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Find video protocols related to scientific articles indexed in Pubmed.
Male lineage strata of Brazilian population disclosed by the simultaneous analysis of STRs and SNPs.
Forensic Sci Int Genet
PUBLISHED: 07-22-2014
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Brazil has a large territory divided in five geographical regions harboring highly diverse populations that resulted from different degrees and modes of admixture between Native Americans, Europeans and Africans. In this study, a sample of 605 unrelated males was genotyped for 17 Y-STRs and 46 Y-SNPs aiming a deep characterization of the male gene pool of Rio de Janeiro and its comparison with other Brazilian populations. High values of Y-STR haplotype diversity (0.9999±0.0001) and Y-SNP haplogroup diversity (0.7589±0.0171) were observed. Population comparisons at both haplotype and haplogroup levels showed significant differences between Brazilian South Eastern and Northern populations that can be explained by differences in the proportion of African and Native American Y chromosomes. Statistical significant differences between admixed urban samples from the five regions of Brazil were not previously detected at haplotype level based on smaller size samples from South East, which emphasizes the importance of sample size to detected population stratification for an accurate interpretation of profile matches in kinship and forensic casework. Although not having an intra-population discrimination power as high as the Y-STRs, the Y-SNPs are more powerful to disclose differences in admixed populations. In this study, the combined analysis of these two types of markers proved to be a good strategy to predict population sub-structure, which should be taken into account when delineating forensic database strategies for Y chromosome haplotypes.
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The peopling of Greenland: further insights from the analysis of genetic diversity using autosomal and X-chromosomal markers.
Eur. J. Hum. Genet.
PUBLISHED: 04-08-2014
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The peopling of Greenland has a complex history shaped by population migrations, isolation and genetic drift. The Greenlanders present a genetic heritage with components of European and Inuit groups; previous studies using uniparentally inherited markers in Greenlanders have reported evidence of a sex-biased, admixed genetic background. This work further explores the genetics of the Greenlanders by analysing autosomal and X-chromosomal data to obtain deeper insights into the factors that shaped the genetic diversity in Greenlanders. Fourteen Greenlandic subsamples from multiple geographical settlements were compared to assess the level of genetic substructure in the Greenlandic population. The results showed low levels of genetic diversity in all sets of the genetic markers studied, together with an increased number of X-chromosomal loci in linkage disequilibrium in relation to the Danish population. In the broader context of worldwide populations, Greenlanders are remarkably different from most populations, but they are genetically closer to some Inuit groups from Alaska. Admixture analyses identified an Inuit component in the Greenlandic population of approximately 80%. The sub-populations of Ammassalik and Nanortalik are the least diverse, presenting the lowest levels of European admixture. Isolation-by-distance analyses showed that only 16% of the genetic substructure of Greenlanders is most likely to be explained by geographic barriers. We suggest that genetic drift and a differentiated settlement history around the island explain most of the genetic substructure of the population in Greenland.European Journal of Human Genetics advance online publication, 7 May 2014; doi:10.1038/ejhg.2014.90.
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Association between Y haplogroups and autosomal AIMs reveals intra-population substructure in Bolivian populations.
Int. J. Legal Med.
PUBLISHED: 04-06-2014
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For the correct evaluation of the weight of genetic evidence in a forensic context, databases must reflect the structure of the population, with all possible groups being represented. Countries with a recent history of admixture between strongly differentiated populations are usually highly heterogeneous and sub-structured. Bolivia is one of these countries, with a high diversity of ethnic groups and different levels of admixture (among Native Americans, Europeans and Africans) across the territory. For a better characterization of the male lineages in Bolivia, 17 Y-STR and 42 Y-SNP loci were genotyped in samples from La Paz and Chuquisaca. Only European and Native American Y-haplogroups were detected, and no sub-Saharan African chromosomes were found. Significant differences were observed between the two samples, with a higher frequency of European lineages in Chuquisaca than in La Paz. A sample belonging to haplogroup Q1a3a1a1-M19 was detected in La Paz, in a haplotype background different from those previously found in Argentina. This result supports an old M19 North-south dispersion in South America, possibly via two routes. When comparing the ancestry of each individual assessed through his Y chromosome with the one estimated using autosomal AIMs, (a) increased European ancestry in individuals with European Y chromosomes and (b) higher Native American ancestry in the carriers of Native American Y-haplogroups were observed, revealing an association between autosomal and Y-chromosomal markers. The results of this study demonstrate that a sub-structure does exist in Bolivia at both inter- and intrapopulation levels, a fact which must be taken into account in the evaluation of forensic genetic evidence.
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Mutation and mutation rates at Y chromosome specific Short Tandem Repeat Polymorphisms (STRs): a reappraisal.
Forensic Sci Int Genet
PUBLISHED: 02-18-2014
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Mutation is a topic of intense research and raises important problems in forensics. Since the markers of choice in current forensic genetics analyses are microsatellites or Short Tandem Repeat Polymorphisms (STRs), mutation is sufficiently common to cause difficulties in evaluating DNA evidence in a significant proportion of cases but at the same time rare enough to turn the estimation of the corresponding probability of occurrence into a hard task. We address these issues using the simplest model of transmission: the Y chromosome specific STRs. Within this model, and under an explicit set of definitions and involved assumptions, we developed the theoretical framework required for the study of allelic transitions in gametogenesis, identifying the required parameters and associated probabilities and finally we discuss the estimation of these parameters and their application in forensics. We conclude that (i) for forensic casework the relevant parameter for incorporation in a likelihood ratio is biallelic specific (i.e. the mutation rate estimate corresponds to the probability of the specific allelic transition observed) and (ii) for these estimates as well as in order to provide data for testing mutation models the absolute frequency of mutated and non-mutated transmissions per allele, along with the description of the observed mutations should be reported.
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Echoes from Sepharad: signatures on the maternal gene pool of crypto-Jewish descendants.
Eur. J. Hum. Genet.
PUBLISHED: 01-24-2014
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The majority of genetic studies on Jewish populations have been focused on Ashkenazim, and genetic data from the Sephardic original source, the Iberian Peninsula, are particularly scarce. Regarding the mitochondrial genome, the available information is limited to a single Portuguese village, Belmonte, where just two different lineages (a single one corresponding to 93.3%) were found in 30 individuals. Aiming at disclosing the ancestral maternal background of the Portuguese Jewry, we enlarged the sampling to other crypto-Jewish descendants in the Bragança district (NE Portugal). Fifty-seven complete mtDNA genomes were newly sequenced and - in contrast with Belmonte - a high level of diversity was found, with five haplogroups (HV0b, N1, T2b11, T2e and U2e) being putatively identified as Sephardic founding lineages. Therefore - in sharp contrast with Belmonte - these communities have managed to escape the expected inbreeding effects caused by centuries of religious repression and have kept a significant proportion of the Sephardic founder gene pool. This deeper analysis of the surviving Sephardic maternal lineages allowed a much more comprehensive and detailed perspective on the origins and survival of the Sephardic genetic heritage. In line with previously published results on Sephardic paternal lineages, our findings also show a surprising resistance to the erosion of genetic diversity in the maternal lineages.European Journal of Human Genetics advance online publication, 30 July 2014; doi:10.1038/ejhg.2014.140.
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A Protocol for mtGenome Analysis on Large Sample Numbers.
Bioinform Biol Insights
PUBLISHED: 01-01-2014
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The mitochondrial genome is widely studied in a variety of fields, such as population, forensic, and human and medical genetics. Most studies have been limited to a small portion of the sequence that, although highly diverse, does not describe the total variability. The arrival of modern high-throughput sequencing technologies has made it possible to investigate larger sequences in a shorter amount of time as well as in a more affordable fashion. This work aims to describe a protocol for sequencing and analyzing the complete mitochondrial genome with the Ion PGM™ platform. To evaluate the protocol, the mitochondrial genome was sequenced to approximately 210 Mbp, with high-quality sequences distributed between 12 samples that had an average coverage of 1023× per sample. Several variant callers were compared to improve the protocol outcome. The results suggest that it is possible to run up to 120 samples per run without any loss of any significant quality. Therefore, this protocol is an efficient and accurate tool for full mitochondrial genome analysis.
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Evaluating the X chromosome-specific diversity of Colombian populations using insertion/deletion polymorphisms.
PLoS ONE
PUBLISHED: 01-01-2014
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The European and African contribution to the pre-existing Native American background has influenced the complex genetic pool of Colombia. Because colonisation was not homogeneous in this country, current populations are, therefore, expected to have different proportions of Native American, European and African ancestral contributions. The aim of this work was to examine 11 urban admixed populations and a Native American group, called Pastos, for 32 X chromosome indel markers to expand the current knowledge concerning the genetic background of Colombia. The results revealed a highly diverse genetic background comprising all admixed populations, harbouring important X chromosome contributions from all continental source populations. In addition, Colombia is genetically sub-structured, with different proportions of European and African influxes depending on the regions. The samples from the North Pacific and Caribbean coasts have a high African ancestry, showing the highest levels of diversity. The sample from the South Andean region showed the lowest diversity and significantly higher proportion of Native American ancestry than the other samples from the North Pacific and Caribbean coasts, Central-West and Central-East Andean regions, and the Orinoquian region. The results of admixture analysis using X-chromosomal markers suggest that the high proportion of African ancestry in the North Pacific coast was primarily male driven. These men have joined to females with higher Native American and European ancestry (likely resulting from a classic colonial asymmetric mating type: European male x Amerindian female). This high proportion of male-mediated African contributions is atypical of colonial settings, suggesting that the admixture occurred during a period when African people were no longer enslaved. In the remaining regions, the African contribution was primarily female-mediated, whereas the European counterpart was primarily male driven and the Native American ancestry contribution was not gender biased.
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Colombias racial crucible: Y chromosome evidence from six admixed communities in the Department of Bolivar.
Ann. Hum. Biol.
PUBLISHED: 11-11-2013
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Abstract Objectives: To determine the African, European and Native-American paternal contributions in genetic samples from the Department of Bolivar (Colombia) with the aims of establishing (1) possible population substructures, and (2) the proportion of biological African heritage in admixed populations of European, Amerindian, and African descent. Methods: Y-SNPs were typed in samples from six communities, including Palenque (renowned for its African linguistic and cultural heritage). Results: Findings reveal a high diversity of Y-haplogroups. With the exception of Palenque, the sum of European male lineages uniformly exceeded 57%. In Palenque, African lineages accounted for 57.7% of its chromosomes, with European male lineages constituting a mere 38.5%. In Pinillos, a significant proportion (23.8%) of the chromosomes belongs to the Native American haplogroup Q1a3a*-M3. Genetic differentiation analyses reveal significant divergences in most pairwise comparisons among the Bolivar municipalities, and the same holds between Bolivar and other South American populations. Conclusions: Heterogeneous patterns of admixture reveal a genetic substructure within the Department of Bolivar. On the paternal side, five out of the six communities studied exhibit a predominantly European gene pool. The exception is Palenque, where European input (38%) is more significant than we had expected.
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Continent-wide decoupling of Y-chromosomal genetic variation from language and geography in native South Americans.
PLoS Genet.
PUBLISHED: 04-01-2013
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Numerous studies of human populations in Europe and Asia have revealed a concordance between their extant genetic structure and the prevailing regional pattern of geography and language. For native South Americans, however, such evidence has been lacking so far. Therefore, we examined the relationship between Y-chromosomal genotype on the one hand, and male geographic origin and linguistic affiliation on the other, in the largest study of South American natives to date in terms of sampled individuals and populations. A total of 1,011 individuals, representing 50 tribal populations from 81 settlements, were genotyped for up to 17 short tandem repeat (STR) markers and 16 single nucleotide polymorphisms (Y-SNPs), the latter resolving phylogenetic lineages Q and C. Virtually no structure became apparent for the extant Y-chromosomal genetic variation of South American males that could sensibly be related to their inter-tribal geographic and linguistic relationships. This continent-wide decoupling is consistent with a rapid peopling of the continent followed by long periods of isolation in small groups. Furthermore, for the first time, we identified a distinct geographical cluster of Y-SNP lineages C-M217 (C3*) in South America. Such haplotypes are virtually absent from North and Central America, but occur at high frequency in Asia. Together with the locally confined Y-STR autocorrelation observed in our study as a whole, the available data therefore suggest a late introduction of C3* into South America no more than 6,000 years ago, perhaps via coastal or trans-Pacific routes. Extensive simulations revealed that the observed lack of haplogroup C3* among extant North and Central American natives is only compatible with low levels of migration between the ancestor populations of C3* carriers and non-carriers. In summary, our data highlight the fact that a pronounced correlation between genetic and geographic/cultural structure can only be expected under very specific conditions, most of which are likely not to have been met by the ancestors of native South Americans.
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Comparison of the genetic background of different Colombian populations using the SNPforID 52plex identification panel.
Int. J. Legal Med.
PUBLISHED: 03-10-2013
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Various strategies for analysing SNP markers and genotyping have been published with the goal of obtaining informative profiles from biological samples that contain only small amounts of template and/or degraded DNA. In this study, a multiplex assay of 52 autosomal single-nucleotide polymorphisms (SNPs) was used to analyse 438 individuals from urban populations from different regions of Colombia, as well as a sample of 50 Native American individuals of the Pastos ethnic group from Nariño. To determine if significant differences in these 52 SNPs exist between the distinct regions of Colombia, genetic distance and admixture analyses were performed based on the available data for 17 different Colombian population groups and for population groups from Africa, Europe and America. The results demonstrate significant differences between the populations from the Southwest Andean, Central-West Andean, Central-East Andean, Orinoquian and northern Colombian Pacific Coast regions. Most of the regions exhibited a European and Native American admixture. One exception is the population from the region of Chocó (on the northern Pacific Coast), which exhibits a high proportion of African admixture (54 %). From the observed genetic backgrounds, it is possible to conclude that a single reference database for the entire country would not be suitable for forensic purposes. The allele frequencies and the forensically relevant parameters were calculated for all of the markers in each Colombian region with significant values for the combined matching probability (power of discrimination ?0.99999999999999990) and the combined probability of exclusion (?0.9990) in trios that were obtained from all of the population groups.
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Paternity exclusion power: comparative behaviour of autosomal and X-chromosomal markers in standard and deficient cases with inbreeding.
Forensic Sci Int Genet
PUBLISHED: 01-09-2013
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In paternity testing the informativeness of genetic markers is traditionally measured through the probability of finding, in randomly chosen individuals, inconsistencies with parent to child Mendelian rules of transmission. This statistic, called power of exclusion (PE), paternal exclusion chance or probability, can be defined for duos (mother not typed) or trios (random false fathers are matched against mother/child pairs) and performed both for autosomal and X-chromosomal markers (restricted to paternity testing involving daughters). PE is an a priori statistic, in the sense of not depending on the individuals genetic data of a case, being dependent however on the estimates of genetic markers allele (or haplotype) frequencies. We have studied the behaviour of this statistic in situations where the randomness assumption is not met, because either (a) the alleged - and false - father is related to the true one, or (b) there is a non-negligible level of background relatedness in the population. For the first case, we derived general (autosomal and X-chromosomal) PE formulas for duos and trios for any genealogy linking alleged father and child, highlighting that the PE of each marker only depends on a single kinship parameter associated with their pedigree. In this case we also estimate a lower bound for the number of extra markers needed to be analysed to achieve the same global power as for unrelated individuals. In the second situation, we demonstrate that for realistic values of the coancestry coefficient the decrease in PE due to population inbreeding is very moderate even when duos are analysed. In this work, beyond the aforementioned issues, we also discuss the suitability of assuming the pedigree father-daughter for calculating the X-PE, since X-markers are not the tool of choice in laboratorial routine when the alleged father is available for testing. Indeed, X-markers are particularly useful in situations where the alleged father is not available for testing but experts are able to type the mother or a daughter of his. Such increase of power is due to the paternal genealogies: half- and full-sisters, and grandmother-granddaughter, having a non-null X-PE even when only duos are analysed in contrast to what happens for autosomes. Algebraic expressions for these cases are also presented.
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High-Throughput Sequencing of a South American Amerindian.
PLoS ONE
PUBLISHED: 01-01-2013
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The emergence of next-generation sequencing technologies allowed access to the vast amounts of information that are contained in the human genome. This information has contributed to the understanding of individual and population-based variability and improved the understanding of the evolutionary history of different human groups. However, the genome of a representative of the Amerindian populations had not been previously sequenced. Thus, the genome of an individual from a South American tribe was completely sequenced to further the understanding of the genetic variability of Amerindians. A total of 36.8 giga base pairs (Gbp) were sequenced and aligned with the human genome. These Gbp corresponded to 95.92% of the human genome with an estimated miscall rate of 0.0035 per sequenced bp. The data obtained from the alignment were used for SNP (single-nucleotide) and INDEL (insertion-deletion) calling, which resulted in the identification of 502,017 polymorphisms, of which 32,275 were potentially new high-confidence SNPs and 33,795 new INDELs, specific of South Native American populations. The authenticity of the sample as a member of the South Native American populations was confirmed through the analysis of the uniparental (maternal and paternal) lineages. The autosomal comparison distinguished the investigated sample from others continental populations and revealed a close relation to the Eastern Asian populations and Aboriginal Australian. Although, the findings did not discard the classical model of America settlement; it brought new insides to the understanding of the human population history. The present study indicates a remarkable genetic variability in human populations that must still be identified and contributes to the understanding of the genetic variability of South Native American populations and of the human populations history.
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SNaPAfu: A Novel Single Nucleotide Polymorphism Multiplex Assay for Aspergillus fumigatus Direct Detection, Identification and Genotyping in Clinical Specimens.
PLoS ONE
PUBLISHED: 01-01-2013
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Early diagnosis of invasive aspergillosis is essential for positive patient outcome. Likewise genotyping of fungal isolates is desirable for outbreak control in clinical setting. We designed a molecular assay that combines detection, identification, and genotyping of Aspergillus fumigatus in a single reaction.
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Revisiting the genetic ancestry of Brazilians using autosomal AIM-Indels.
PLoS ONE
PUBLISHED: 01-01-2013
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There are many different studies that contribute to the global picture of the ethnic heterogeneity in Brazilian populations. These studies use different types of genetic markers and are focused on the comparison of populations at different levels. In some of them, each geographical region is treated as a single homogeneous population, whereas other studies create different subdivisions: political (e.g., pooling populations by State), demographic (e.g., urban and rural), or ethnic (e.g., culture, self-declaration, or skin colour). In this study, we performed an enhanced reassessment of the genetic ancestry of ~ 1,300 Brazilians characterised for 46 autosomal Ancestry Informative Markers (AIMs). In addition, 798 individuals from twelve Brazilian populations representing the five geographical macro-regions of Brazil were newly genotyped, including a Native American community and a rural Amazonian community. Following an increasing North to South gradient, European ancestry was the most prevalent in all urban populations (with values up to 74%). The populations in the North consisted of a significant proportion of Native American ancestry that was about two times higher than the African contribution. Conversely, in the Northeast, Center-West and Southeast, African ancestry was the second most prevalent. At an intrapopulation level, all urban populations were highly admixed, and most of the variation in ancestry proportions was observed between individuals within each population rather than among population. Nevertheless, individuals with a high proportion of Native American ancestry are only found in the samples from Terena and Santa Isabel. Our results allowed us to further refine the genetic landscape of Brazilians while establishing the basis for the effective application of an autosomal AIM panel in forensic casework and clinical association studies within the highly admixed Brazilian populations.
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SNaPaer: a practical single nucleotide polymorphism multiplex assay for genotyping of Pseudomonas aeruginosa.
PLoS ONE
PUBLISHED: 01-01-2013
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Multilocus sequence typing (MLST) represents the gold standard genotyping method in studies concerning microbial population structure, being particularly helpful in the detection of clonal relatedness. However, its applicability on large-scale genotyping is limited due to the high cost and time spent on the task. The selection of the most informative nucleotide positions simplifies genomic characterization of bacteria. A simple and informative multiplex, SNaPaer assay, was developed and genotyping of Pseudomonas aeruginosa was obtained after a single reaction of multiplex PCR amplification and mini-sequencing. This cost-effective technique allowed the analysis of a Portuguese set of isolates (n?=?111) collected from three distinct hospitals and the genotyping data could be obtained in less than six hours. Point mutations were shown to be the most frequent event responsible for diversification of the Portuguese population sample. The Portuguese isolates corroborated the epidemic hypothesis for P. aeruginosa population. SNaPaer genotyping assay provided a discriminatory power of 0.9993 for P. aeruginosa, by testing in silico several hundreds of MLST profiles available online. The newly proposed assay targets less than 0.01% of the total MLST length and guarantees reproducibility, unambiguous analysis and the possibility of comparing and transferring data between different laboratories. The plasticity of the method still supports the addition of extra molecular markers targeting specific purposes/populations. SNaPaer can be of great value to clinical laboratories by facilitating routine genotyping of P. aeruginosa.
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Allele frequencies for 15 autosomal STR markers in the Libyan population.
Ann. Hum. Biol.
PUBLISHED: 11-01-2011
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Until recently Libya remained the only state of the Maghreb without genetic evolution investigations of the genetic landscape of its population. Apart from some studies of Libyan Jews and Libyan Tuareg, only two recent investigations, based on autosomal ancestry informative SNP and mitochondrial DNA markers, have concerned the general Libyan population.
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The peopling of Europe and the cautionary tale of Y chromosome lineage R-M269.
Proc. Biol. Sci.
PUBLISHED: 08-24-2011
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Recently, the debate on the origins of the major European Y chromosome haplogroup R1b1b2-M269 has reignited, and opinion has moved away from Palaeolithic origins to the notion of a younger Neolithic spread of these chromosomes from the Near East. Here, we address this debate by investigating frequency patterns and diversity in the largest collection of R1b1b2-M269 chromosomes yet assembled. Our analysis reveals no geographical trends in diversity, in contradiction to expectation under the Neolithic hypothesis, and suggests an alternative explanation for the apparent cline in diversity recently described. We further investigate the young, STR-based time to the most recent common ancestor estimates proposed so far for R-M269-related lineages and find evidence for an appreciable effect of microsatellite choice on age estimates. As a consequence, the existing data and tools are insufficient to make credible estimates for the age of this haplogroup, and conclusions about the timing of its origin and dispersal should be viewed with a large degree of caution.
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A method for the analysis of 32 X chromosome insertion deletion polymorphisms in a single PCR.
Int. J. Legal Med.
PUBLISHED: 04-22-2011
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Studies of human genetic variation predominantly use short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) but Insertion deletion polymorphisms (Indels) are being increasingly explored. They combine desirable characteristics of other genetic markers, especially the possibility of being analysed using short amplicon strategies, which increases the ease of analysis, contributing to justify their interest in population and forensic genetics. After the advent of autosomal and uniparental genomes (mtDNA and Y chromosome), these fields of research are also focusing on the X chromosome, given its special transmission pattern. The X chromosome markers brought new insights into the history of modern human populations and also proved useful in forensic kinship investigations, namely in deficient relationship cases and in cases where autosomes are uninformative. This work describes an X-Indel multiplex system amplifying 32 biallelic markers in one single PCR. The multiplex includes X-Indels shown to be polymorphic in the major human population groups and follows a short amplicon strategy. The set was applied in the genetic characterization of sub-Saharan African, European and East Asian population samples and revealed high forensic efficiency, as measured by the accumulated power of discrimination (0.9999990 was the lowest value in males and 0.999999999998 was the highest in females) and mean exclusion chance varied between 0.998 and 0.9996 in duos and between 0.99997 and 0.999998 in trios. Finally, a segregation analysis was performed using trio constellations of father-mother-daughters in order to address the transmission pattern and assess mutation rates of this type of markers.
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Rapid identification of Aspergillus fumigatus within the section Fumigati.
BMC Microbiol.
PUBLISHED: 03-01-2011
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New fungal species that are morphologically similar to Aspergillus fumigatus were recently described and included in section Fumigati. Misidentification of such fungal species, particularly of the human pathogens, Aspergillus lentulus, Neosartorya fischeri, Neosartorya hiratsukae, Neosartorya pseudofischeri and Neosartorya udagawae, has been increasingly reported by numerous clinical labs. Nevertheless, A. fumigatus still accounts for more than 90% of all invasive aspergillosis cases. The purpose of the present study was to develop a rapid method for the molecular identification of A. fumigatus to distinguish it from other species within the section Fumigati.
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Y chromosome comparative analysis of Rondônia with other Brazilian populations.
Leg Med (Tokyo)
PUBLISHED: 01-29-2011
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In the present study, a Brazilian population, located in the Rondônia state, was genetically characterized for a set of Y chromosome specific STRs included in the Applied Biosystems kit (AmpF?STR®Yfiler™), which allows the simultaneous amplification of 16 markers: DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a/b, DYS438, DYS439, DYS437, DYS448, DYS456, DYS458, DYS635 and GATA H4. The studied population from Rondônia state, in the North of Brazil, included individuals with admixed Native American, African and European ancestry. When comparing Rondônia with other Brazilian populations no significant genetic distances were found. In the comparison with other worldwide populations, although a predominant male European influence could be detected, there were significant differences with some populations from Central and South America and Africa.
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Male lineages in South American native groups: evidence of M19 traveling south.
Am. J. Phys. Anthropol.
PUBLISHED: 01-19-2011
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With this study, we aimed to determine the different male ancestral components of two Native American communities from Argentina, namely Toba and Colla. The analysis of 27 Y-chromosome SNPs allowed us to identify seven different haplogroups in both samples. Chromosomes carrying the M3 mutation, which typically defines the Native American haplogroup Q1a3a, were seen most frequently in the Toba community (90%). Conversely, Q1a3a was represented in 34% of the Colla Y-chromosomes, whereas haplogroup R1b1, the main representative of western European populations, exhibited the highest frequency in this population (41%). Different M3 sublineages in the Toba community could be identified by observing point mutations at both DYS385 and M19 loci. A microvariant at DYS385, named 16.1, has been characterized, which helps to further subdivide Q1a3a. It is the first time the M19 mutated allele is described in a population from Argentina. This finding supports the old age of the lineages carrying the M19 mutation, but it contradicts the previous hypothesis that the M19 mutated allele is confined to only two Equatorial-Tucano population groups from the north region of South America. The detection of M19 further south than previously thought allows questioning of the hypothesis that this lineage serves as an example of isolation after colonization. This observation also affirms the strong genetic drift to which Native Americans have been subjected. Moreover, our study illustrates a heterogeneous contribution of Europeans to these populations and supports previous studies showing that most Native American groups were subjected to European admixture that primarily involved immigrant men.
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Reconstructing the Indian origin and dispersal of the European Roma: a maternal genetic perspective.
PLoS ONE
PUBLISHED: 01-10-2011
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Previous genetic, anthropological and linguistic studies have shown that Roma (Gypsies) constitute a founder population dispersed throughout Europe whose origins might be traced to the Indian subcontinent. Linguistic and anthropological evidence point to Indo-Aryan ethnic groups from North-western India as the ancestral parental population of Roma. Recently, a strong genetic hint supporting this theory came from a study of a private mutation causing primary congenital glaucoma. In the present study, complete mitochondrial control sequences of Iberian Roma and previously published maternal lineages of other European Roma were analyzed in order to establish the genetic affinities among Roma groups, determine the degree of admixture with neighbouring populations, infer the migration routes followed since the first arrival to Europe, and survey the origin of Roma within the Indian subcontinent. Our results show that the maternal lineage composition in the Roma groups follows a pattern of different migration routes, with several founder effects, and low effective population sizes along their dispersal. Our data allowed the confirmation of a North/West migration route shared by Polish, Lithuanian and Iberian Roma. Additionally, eleven Roma founder lineages were identified and degrees of admixture with host populations were estimated. Finally, the comparison with an extensive database of Indian sequences allowed us to identify the Punjab state, in North-western India, as the putative ancestral homeland of the European Roma, in agreement with previous linguistic and anthropological studies.
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Identification of species by multiplex analysis of variable-length sequences.
Nucleic Acids Res.
PUBLISHED: 10-04-2010
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The quest for a universal and efficient method of identifying species has been a longstanding challenge in biology. Here, we show that accurate identification of species in all domains of life can be accomplished by multiplex analysis of variable-length sequences containing multiple insertion/deletion variants. The new method, called SPInDel, is able to discriminate 93.3% of eukaryotic species from 18 taxonomic groups. We also demonstrate that the identification of prokaryotic and viral species with numeric profiles of fragment lengths is generally straightforward. A computational platform is presented to facilitate the planning of projects and includes a large data set with nearly 1800 numeric profiles for species in all domains of life (1556 for eukaryotes, 105 for prokaryotes and 130 for viruses). Finally, a SPInDel profiling kit for discrimination of 10 mammalian species was successfully validated on highly processed food products with species mixtures and proved to be easily adaptable to multiple screening procedures routinely used in molecular biology laboratories. These results suggest that SPInDel is a reliable and cost-effective method for broad-spectrum species identification that is appropriate for use in suboptimal samples and is amenable to different high-throughput genotyping platforms without the need for DNA sequencing.
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Genetic characterization of uniparental lineages in populations from Southwest Iberia with past malaria endemicity.
Am. J. Hum. Biol.
PUBLISHED: 08-26-2010
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Malaria endemicity in Southwest Iberia afforded conditions for an increase of sickle cell disease (SCD), which in the region follows a clinal pattern toward the south, where foci of high prevalence were found. SCD distribution is associated with specific geographical areas, and therefore, its introduction into Iberia may be related to the migration of different populations. We have analyzed the variation of uniparental markers in Portuguese populations with high frequency of SCD--Coruche, Pias, and Alcacer do Sal--to evaluate if their present-day pattern of neutral diversity could provide evidence about people inhabiting the area over different time periods. Two hundred and eighty-five individuals were sampled in Coruche, Pias, and Alcacer do Sal. All were analyzed for the control region of mitochondrial DNA (mtDNA); males were additionally examined for Y-chromosome markers. Results were then compared with data from other Portuguese and non-Portuguese populations. In Coruche, the genetic profile was similar to the profile usually found in Portugal. In Alcacer do Sal, the frequency of sub-Saharan mtDNA L lineages was the highest ever reported (22%) in Europe. In Pias, mtDNA diversity revealed higher frequencies of Mediterranean haplogroups I, J, and T than usually found in surrounding populations. The presence of Sub-Saharan maternal lineages in Alcacer do Sal is likely associated with the influx of African slaves between the 15th and 19th centuries, whereas in Pias, the Mediterranean influence might be traced to ancient contacts with Greeks, Phoenicians, and Carthaginians, who established important trading networks in southern Iberia.
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International distribution and age estimation of the Portuguese BRCA2 c.156_157insAlu founder mutation.
Breast Cancer Res. Treat.
PUBLISHED: 06-29-2010
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The c.156_157insAlu BRCA2 mutation has so far only been reported in hereditary breast/ovarian cancer (HBOC) families of Portuguese origin. Since this mutation is not detectable using the commonly used screening methodologies and must be specifically sought, we screened for this rearrangement in a total of 5,443 suspected HBOC families from several countries. Whereas the c.156_157insAlu BRCA2 mutation was detected in 11 of 149 suspected HBOC families from Portugal, representing 37.9% of all deleterious mutations, in other countries it was detected only in one proband living in France and in four individuals requesting predictive testing living in France and in the USA, all being Portuguese immigrants. After performing an extensive haplotype study in carrier families, we estimate that this founder mutation occurred 558 ± 215 years ago. We further demonstrate significant quantitative differences regarding the production of the BRCA2 full length RNA and the transcript lacking exon 3 in c.156_157insAlu BRCA2 mutation carriers and in controls. The cumulative incidence of breast cancer in carriers did not differ from that of other BRCA2 and BRCA1 pathogenic mutations. We recommend that all suspected HBOC families from Portugal or with Portuguese ancestry are specifically tested for this rearrangement.
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Study of 25 X-chromosome SNPs in the Portuguese.
Forensic Sci Int Genet
PUBLISHED: 06-27-2010
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The importance of X-chromosome markers in individual identifications, population genetics, forensics and kinship testing is getting wide recognition. In this work, we studied the distributions of 25 X-chromosome single nucleotide polymorphisms (X-SNPs) in population samples from Northern, Central and Southern Portugal (n=305). The data were also compared with previous data from the Mediterranean area confirming a general genetic homogeneity among populations in the region. The X-SNP distribution in the three Portuguese regional samples did not show any significant substructure and the X-SNP distributions did not differ significantly from those of the majority of Mediterranean populations.
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Genetic profile characterization of 10 X-STRs in four populations of the southeastern region of Brazil.
Int. J. Legal Med.
PUBLISHED: 06-02-2010
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Ten X-chromosomal short tandem repeats (DXS8378, DXS9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7133, GATA172D05, GATA31E08 and DXS7423) were analyzed in four populations of the southeastern region of Brazil (São Paulo, Rio de Janeiro, Vitória and Belo Horizonte). No deviations from the Hardy-Weinberg equilibrium were observed for any of the analyzed loci in the four populations. The average diversity per locus varied between 68% for DXS8378, DXS7133, and DXS7423 and 83%, for DXS6809, with Rio de Janeiro being the most diverse population. Overall power of discrimination values in females varied between 0.99999999990 and 0.99999999997 and between 0.9999991 and 0.9999995 in males. These high values show the potential of this system for forensic application and relationships testing in the studied groups. Genetic comparisons (exact tests of population differentiation and pairwise genetic distances) revealed significant differences between Brazilian and other populations from Europe, Latin America and Africa, as well as among different Brazilian populations.
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Malaria: looking for selection signatures in the human PKLR gene region.
Br. J. Haematol.
PUBLISHED: 04-04-2010
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The genetic component of susceptibility to malaria is both complex and multigenic and the better-known protective polymorphisms are those involving erythrocyte-specific structural proteins and enzymes. In vivo and in vitro data have suggested that pyruvate kinase deficiency, which causes a nonspherocytic haemolytic anaemia, could be protective against malaria severity in humans, but this hypothesis remains to be tested. In the present study, we conducted a combined analysis of Short Tandem Repeats (STRs) and Single Nucleotide Polymorphisms (SNPs) in the pyruvate kinase-encoding gene (PKLR) and adjacent regions (chromosome 1q21) to look for malaria selective signatures in two sub-Saharan African populations from Angola and Mozambique, in several groups with different malaria infection outcome. A European population from Portugal, including a control and a pyruvate kinase-deficient group, was used for comparison. Data from STR and SNP loci spread along the PKLR gene region showed a considerably higher differentiation between African and Portuguese populations than that usually found for neutral markers. In addition, a wider region showing strong linkage disequilibrium was found in an uncomplicated malaria group, and a haplotype was found to be associated with this clinical group. Altogether, this data suggests that malaria selective pressure is acting in this genomic region.
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Analysis of paternal lineages in Brazilian and African populations.
Genet. Mol. Biol.
PUBLISHED: 02-23-2010
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The present-day Brazilian population is a consequence of the admixture of various peoples of very different origins, namely, Amerindians, Europeans and Africans. The proportion of each genetic contribution is known to be very heterogeneous throughout the country. The aim of the present study was to compare the male lineages present in two distinct Brazilian populations, as well as to evaluate the African contribution to their male genetic substrate. Thus, two Brazilian population samples from Manaus (State of Amazon) and Ribeirão Preto (State of São Paulo) and three African samples from Guinea Bissau, Angola and Mozambique were typed for a set of nine Y chromosome specific STRs. The data were compared with those from African, Amerindian and European populations. By using Y-STR haplotype information, low genetic distances were found between the Manaus and Ribeirão Preto populations, as well as between these and others from Iberia. Likewise, no significant distances were observed between any of the African samples from Angola, Mozambique and Guinea Bissau. Highly significant Rst values were found between both Brazilian samples and all the African and Amerindian populations. The absence of a significant Sub-Saharan African male component resulting from the slave trade, and the low frequency in Amerindian ancestry Y-lineages in the Manaus and Ribeirão Preto population samples are in accordance with the accentuated gender asymmetry in admixture processes that has been systematically reported in colonial South American populations.
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Genetic diversity of Aspergillus fumigatus in indoor hospital environments.
Med. Mycol.
PUBLISHED: 02-09-2010
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Environmental isolates of Aspergillus fumigatus are less studied than those recovered from clinical sources. In the present study, the genetic diversity among such environmental isolates was assessed, as well as their dispersion ability and the acquisition of new strains in 19 medical units of the same hospital. A. fumigatus isolates were genotyped using a single multiplex PCR-based reaction with eight microsatellite markers and an insertion/deletion polymorphism. A total of 130 unique genotypes were found among a total of 250 A. fumigatus isolates. Genotypic diversity ranged from 0.86 to 1 in samples from hospital rooms, and there was no correlation between these samples and the presence of high-efficiency particulate air filters or any other air filtration system. Four of the six most prevalent A. fumigatus strains were recovered from water samples. The occurrence of microvariation was common among environmental isolates, which affected each of the microsatellite markers. The assessment of the genetic diversity of A. fumigatus is a useful tool for illustrating the presence or absence of specific clonal populations in a clinical setting. A. fumigatus populations were highly dynamic indoors, and new populations were found in just a few months. Due to the high indoor dispersion capability of A. fumigatus, more attention should be given to strains with increased pathogenic potential or reduced susceptibility to anti-fungal drugs.
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Digging deeper into East African human Y chromosome lineages.
Hum. Genet.
PUBLISHED: 02-02-2010
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The most significant and widely studied remodeling of the African genetic landscape is the Bantu expansion, which led to an almost total replacement of the previous populations from the sub-Saharan region. However, a poor knowledge exists about other population movements, namely, the Nilotic migration, which is a pastoralist dispersal that, contrary to the Bantu expansion, impacted only East African populations. Here, samples from a Ugandan Nilotic-speaking population were studied for 37 Y chromosome-specific SNPs, and the obtained data were compared with those already available for other sub-Saharan population groups. Although Uganda lies on the fringe of both Bantu and Nilotic expansions, a low admixture with Bantu populations was detected, with haplogroups carrying M13, M182 and M75 mutations prevailing in Nilotes together with a low frequency of the main Bantu haplogroups from clade E1b1a-M2. The results of a comparative analysis with data from other population groups allowed a deeper characterization of some lineages in our sample, clarifying some doubts about the origin of some particular Y-SNPs in different ethnic groups, such as M150, M112 and M75. Moreover, it was also possible to identify a new Y-SNP apparently specific to Nilotic groups, as well as the presence of particular haplogroups that characterize Nilotic populations. The detection of a new haplogroup B2a1b defined by G1, could be, therefore, important to differentiate Nilotes from other groups, helping to trace migration and admixture events that occurred in eastern Africa.
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X-chromosome markers in kinship testing: a generalisation of the IBD approach identifying situations where their contribution is crucial.
Forensic Sci Int Genet
PUBLISHED: 01-15-2010
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The standard practice of forensic kinship evaluation uses unlinked autosomal markers. However, X-chromosome markers have recently gained recognition as a powerful tool to complement the information provided by autosomes, particularly in complex cases. In this paper, the X-chromosome mode of transmission is addressed in the theoretical identity-by-descent framework. Formulas for the joint genotypic probabilities considering various pedigrees relating two inbred and/or non-inbred individuals are derived. Finally, the importance of X-chromosome markers is highlighted by the fact that, in addition to complementing the autosomal information, X-chromosome transmission allows differential weighting of certain hypotheses regarding pedigrees belonging to the same autosomal class, i.e., pedigrees that are indistinguishable by the use of unlinked autosomal markers. Illustrative examples of common kinship testing are shown.
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Genetic analysis of 10 X-STRs in Argentinian population.
Forensic Sci Int Genet
PUBLISHED: 01-04-2010
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A set of 200 samples, 100 males and 100 females, obtained from unrelated Argentinean donors were analyzed using 10 X-STRs-DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS7423, DXS6809, DXS7132, DXS9902 and DXS6789-in order to obtain allele frequencies. Statistical analysis was performed using Powerstats and Arlequin software. The population showed no deviation from Hardy Weinberg equilibrium at all loci analyzed. Allele frequencies were compared with Spanish and Portuguese sample sets showing no statistical significant differences in four of the 10 markers analyzed. The most polymorphic marker was DXS6809 and the high values of combined power of exclusion (99.9993355% in trios and 99.9715450% in duos) reinforce the usefulness of this set of markers for kinship test and human identification.
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Allele-specific CDH1 downregulation and hereditary diffuse gastric cancer.
Hum. Mol. Genet.
PUBLISHED: 12-04-2009
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Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant cancer susceptibility syndrome characterized by early-onset diffuse gastric cancer (DGC) and lobular breast cancer. E-cadherin (CDH1) heterozygous germline mutations and deletions are found in 40% of families. Independent of CDH1 alterations, most HDGC tumours display mislocalized or absent E-cadherin immunoexpression, therefore undetected defects at the CDH1 locus may still be involved. We aimed at determining whether CDH1 mutation-negative probands display germline CDH1 allele-specific expression (ASE) imbalance, using a single-nucleotide primer extension-based procedure and tried to uncover the underlying molecular defect. CDH1 ASE analysis was performed using three intragenic SNPs in RNA extracted from the blood of 21 cancer-free individuals and 22 HDGC probands (5 CDH1 mutation carriers and 17 CDH1 negative). Germline promoter methylation, deletions and haplotype-related susceptibility at the CDH1 locus were analysed. Both CDH1 alleles from cancer-free individuals displayed equivalent expression levels, whereas monoallelic CDH1 expression or high allelic expression imbalance (AI) was present in 80% of CDH1 mutant and 70.6% (n = 12) of CDH1-negative HDGC probands. Germline deletions and promoter hypermethylation were found in 25% of probands displaying high CDH1 AI. No particular haplotype was found to be associated with CDH1 high AI. Germline CDH1 AI is highly frequent among CDH1 mutation-negative probands but was not seen in cancer-free individuals. This implicates the CDH1 locus in the majority of mutation-negative HDGC families.
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A new multiplex for human identification using insertion/deletion polymorphisms.
Electrophoresis
PUBLISHED: 10-29-2009
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Human identification is usually based on the study of STRs or SNPs depending on the particular characteristics of the investigation. However, other types of genetic variation such as insertion/deletion polymorphisms (indels) have considerable potential in the field of identification, since they can combine the desirable characteristics of both STRs and SNPs. In this study, a set of 38 non-coding bi-allelic autosomal indels reported to be polymorphic in African, European, and Asian populations were selected. We developed a sensitive genotyping assay, which is able to characterize all 38 bi-allelic markers using a single multiplex PCR and detected with standard CE analyzers. Amplicon length was designed to be shorter than 160 bp. Complete profiles were obtained using 0.3 ng of DNA, and full genotyping of degraded samples was possible in cases where standard STR typing had partially failed. A total of 306 individuals from Angola, Mozambique, Portugal, Macau, and Taiwan were studied and population data are presented. All indels were polymorphic in the three population groups studied and the random match probabilities of the set ranged in orders of magnitude from 10(-14) to 10(-15). Therefore, the indel-plex represents a valuable approach in human identification studies, especially in challenging DNA cases, as a more straightforward and efficient alternative to SNP typing.
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Tracing the history of goat pastoralism: new clues from mitochondrial and Y chromosome DNA in North Africa.
Mol. Biol. Evol.
PUBLISHED: 09-03-2009
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Valuable insights into the history of human populations have been obtained by studying the genetic composition of their domesticated species. Here we address some of the long-standing questions about the origin and subsequent movements of goat pastoralism in Northern Africa. We present the first study combining results from mitochondrial DNA (mtDNA) and Y chromosome loci for the genetic characterization of a domestic goat population. Our analyses indicate a remarkably high diversity of maternal and paternal lineages in a sample of indigenous goats from the northwestern fringe of the African continent. Median-joining networks and a multidimensional scaling of ours and almost 2000 published mtDNA sequences revealed a considerable genetic affinity between goat populations from the Maghreb (Northwest Africa) and the Near East. It has been previously shown that goats have a weak phylogeographic structure compatible with high levels of gene flow, as demonstrated by the worldwide dispersal of the predominant mtDNA haplogroup A. In contrast, our results revealed a strong correlation between genetic and geographical distances in 20 populations from different regions of the world. The distribution of Y chromosome haplotypes in Maghrebi goats indicates a common origin for goat patrilines in both Mediterranean coastal regions. Taken together, these results suggest that the colonization and subsequent dispersal of domestic goats in Northern Africa was influenced by the maritime diffusion throughout the Mediterranean Sea and its coastal regions of pastoralist societies whose economy included goat herding. Finally, we also detected traces of gene flow between goat populations from the Maghreb and the Iberian Peninsula corroborating evidence of past cultural and commercial contacts across the Strait of Gibraltar.
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The Karimojong from Uganda: genetic characterization using an X-STR decaplex system.
Forensic Sci Int Genet
PUBLISHED: 08-04-2009
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The Karimojong, an African group from the Karamoja region of Northeast Uganda, were genetically analysed using a decaplex system for X chromosome short tandem repeats (X-STRs). A total of 255 individuals (117 males and 138 females) were genotyped for the following loci: DXS8378, DXS9898, DXS7133, GATA31E08, GATA172D05, DXS7423, DXS6809, DXS7132, DXS9902 and DXS6789. Allele frequencies and parameters for forensic evaluation were calculated for each STR. No association was found between any pairs of loci studied. DXS6789 was the most polymorphic marker in this sample, followed by DXS6809, with gene diversities of 84.79% and 83.94%, respectively. The less discriminating locus observed was DXS7133, with a gene diversity of 39.79%. High overall values of power of discrimination were obtained for female (1 in 1.8 x 10(10)) and male samples (1 in 1.6 x 10(6)), as well as high power of exclusion in father/mother/daughter trios (99.9997%), in father daughter duos (99.9862%) and in half sisters with same father (99.0331%). These results confirm the potential of this 10-plex in parentage testing and in human identification.
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A GEP-ISFG collaborative study on the optimization of an X-STR decaplex: data on 15 Iberian and Latin American populations.
Int. J. Legal Med.
PUBLISHED: 08-04-2009
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In a collaborative work carried out by the Spanish and Portuguese ISFG Working Group (GEP-ISFG), a polymerase chain reaction multiplex was optimized in order to type ten X-chromosome short tandem repeats (STRs) in a single reaction, including: DXS8378, DXS9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7133, GATA172D05, GATA31E08, and DXS7423. Using this X-decaplex, each 17 of the participating laboratories typed a population sample of approximately 200 unrelated individuals (100 males and 100 females). In this work, we report the allele frequencies for the ten X-STRs in 15 samples from Argentina (Buenos Aires, Córdoba, Río Negro, Entre Ríos, and Misiones), Brazil (São Paulo, Rio de Janeiro, Paraná, and Mato Grosso do Sul), Colombia (Antioquia), Costa Rica, Portugal (Northern and Central regions), and Spain (Galicia and Cantabria). Gene diversities were calculated for the ten markers in each population and all values were above 56%. The average diversity per locus varied between 66%, for DXS7133, and 82%, for DXS6809. For this set of STRs, a high discrimination power was obtained in all populations, both in males (> or =1 in 5 x 10(5)) and females (> or =1 in 3 x 10(9)), as well as high mean exclusion chance in father/daughter duos (> or =99.953%) and in father/mother/daughter trios (> or =99.999%). Genetic distance analysis showed no significant differences between northern and central Portugal or between the two Spanish samples from Galicia and Cantabria. Inside Brazil, significant differences were found between Rio de Janeiro and the other three populations, as well as between São Paulo and Paraná. For the five Argentinean samples, significant distances were only observed when comparing Misiones with Entre Ríos and with Río Negro, the only two samples that do not differ significantly from Costa Rica. Antioquia differed from all other samples, except the one from Río Negro.
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Analysis of malaria associated genetic traits in Cabo Verde, a melting pot of European and sub Saharan settlers.
Blood Cells Mol. Dis.
PUBLISHED: 07-31-2009
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Malaria has occurred in the Cabo Verde archipelago with epidemic characteristics since its colonization. Nowadays, it occurs in Santiago Island alone and though prophylaxis is not recommended by the World Health Organization, studies have highlight the prospect of malaria becoming a serious public health problem as a result of the presence of antimalarial drug resistance associated with mutations in the parasite populations and underscore the need for tighter surveillance. Despite the presumptive weak immune status of the population, severe symptoms of malaria are not observed and many people present a subclinical course of the disease. No data on the prevalence of sickle-cell trait and red cell glucose-6-phosphate dehydrogenase deficiency (two classical genetic factors associated with resistance to severe malaria) were available for the Cabo Verde archipelago and, therefore, we studied the low morbidity from malaria in relation to the particular genetic characteristics of the human host population. We also included the analysis of the pyruvate kinase deficiency associated gene, reported as putatively associated with resistance to the disease. Allelic frequencies of the polymorphisms examined are closer to European than to African populations and no malaria selection signatures were found. No association was found between the analyzed human factors and infection but one result is of high interest: a linkage disequilibrium test revealed an association of distant loci in the PKLR gene and adjacent regions, only in non-infected individuals. This could mean a more conserved gene region selected in association to protection against the infection and/or the disease.
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Assessing interethnic admixture using an X-linked insertion-deletion multiplex.
Am. J. Hum. Biol.
PUBLISHED: 06-18-2009
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In this study, a PCR multiplex was optimized, allowing the simultaneous analysis of 13 X-chromosome Insertion/deletion polymorphisms (INDELs). Genetic variation observed in Africans, Europeans, and Native Americans reveals high inter-population variability. The estimated proportions of X-chromosomes in an admixed population from the Brazilian Amazon region show a predominant Amerindian contribution (approximately 41%), followed by European (approximately 32%) and African (approximately 27%) contributions. The proportion of Amerindian contribution based on X-linked data is similar to the expected value based on mtDNA and Y-chromosome information. The accuracy for assessing interethnic admixture, and the high differentiation between African, European, and Native American populations, demonstrates the suitability of this INDEL set to measure ancestry proportions in three-hybrid populations, as it is the case of Latin American populations.
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Nilotes from Karamoja, Uganda: haplotype data defined by 17 Y-chromosome STRs.
Forensic Sci Int Genet
PUBLISHED: 06-17-2009
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In this work 118 Nilote male samples were genotyped from Karamoja region, in Northeast Uganda, through 17 Y-chromosomal short tandem repeats (STRs)-DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385, DYS437, DYS438, DYS439, DYS448, DYS456, DYS458, DYS635 and GATA H4.1. A total of 94 different haplotypes were found, where 19 were shared by at least two individuals, and haplotype diversity amounted to 0.9958+/-0.0017. When considering only the nine Y-STRs included in the minimal haplotype (YHRD) the haplotype diversity decreased to 0.9807+/-0.0048, a similar value to those found in other African populations such as Mozambique, Angola and Guinea-Bissau. Population comparisons were performed between our sample and nine other African populations. Significant R(st) genetic distances were obtained between the Nilote population from Karamoja and all African populations used for comparison, except Xhosa sample from South Africa. In the multidimensional scaling (MDS) plot, the Karamoja sample is well separated from all other populations, standing between the Ethiopia and the Bantu samples, although closer to this last group.
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X-chromosome STR sequence variation, repeat structure, and nomenclature in humans and chimpanzees.
Int. J. Legal Med.
PUBLISHED: 06-17-2009
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Qualitative information on the sequence composition of the allele and locus structure of the X-STRs DXS8378, DXS9898, DXS6789, GATA31E08, and GATA172D05 was generated in this study. Sequence data were obtained from chimpanzees (Pan troglodytes) and diverse human population groups including Africans, Caucasians, Asians, African-Americans, and Hispanics. Results revealed DXS8378 as the most stable locus. On the other hand, DXS9898 and GATA172D05 showed unstable regions identified through chimpanzee-human sequence comparison. At DXS6789, intra-allelic variation was found in all human populations, i.e., alleles with same fragment sizes showed structural differences only detected by sequencing. At the GATA31E08 locus, a previously unreported variation between humans and chimpanzees was identified in an adjacent region upstream from the repeat. This resulted in the addition of two repeat units and the proposal of a new allele nomenclature at this locus. Also, the sequence analyses did not detect ethnic differences between the studied population samples that would justify the use of these markers to help identify ethnic origin in an anthropological context.
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An INDEL polymorphism at the X-STR GATA172D05 flanking region.
Int. J. Legal Med.
PUBLISHED: 06-17-2009
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A new polymorphic INDEL was detected at the X-STR GATA172D05 flanking region, which corresponds to an 18-bp deletion, 141 bp upstream the TAGA repeat motif. This INDEL was found to be polymorphic in different population samples from Native Americans, Africans, and Europeans as well as in an admixed population from the Amazonia (Belém). Gene diversities varied between 37.5% in Native Americans and 49.9% in Africans. Comparison between human and chimpanzee sequences showed that the ancestral state corresponds to the presence of two copies of 18 bp, detected in both species; and the mutated allele has lost one of these two copies. The simultaneous analysis of the short tandem repeat (STR) and INDEL variation showed an association between the INDEL ancestral allele with the shorter STR alleles. High diversities were found in all population groups when combining the information provided by the INDEL and STR variation. Gene diversities varied between 76.7% in Native Americans and 80.6% in both Portugal and Belém.
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An X-chromosome pentaplex in two linkage groups: haplotype data in Alagoas and Rio de Janeiro populations from Brazil.
Forensic Sci Int Genet
PUBLISHED: 06-15-2009
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Genotype data were obtained for five X-Chr STRs (DXS10079, DXS10074, DXS10075, DXS7424 and DXS101) in two different populations from Brazil, namely Alagoas and Rio de Janeiro. Observed genotype distributions in female samples for each locus do not show deviations from Hardy-Weinberg equilibrium expectations. Gametic association was tested for all pairs of loci in male samples. Significant association values were found between all pairs including DXS10079, DXS10074 and DXS10075, as well as between DXS7424 and DXS101, proving that these two groups of markers must be treated as haplotypes. No significant association could be found between markers from the two groups (DXS10079, DXS10074 or DXS10075 vs. DXS7424 or DXS101), although distances between them varied from 24 to 25cM. When comparing haplotype frequencies in Alagoas, Rio de Janeiro, Germany and Ghana, significant differences were found between the Brazilian and the Germany sample and that from Ghana. Nevertheless, no significant differences were found between Alagoas and Rio de Janeiro, as well as between these two populations and Germany. The combined power of discrimination in males and females were high in both Brazilian populations (>or=0.9996 and >or=0.9999998, respectively), showing the utility of these markers for human identification and paternity testing.
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Population data for 12 Y-chromosome STR loci in a sample from El Salvador.
Leg Med (Tokyo)
PUBLISHED: 06-11-2009
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Haplotype, allele frequencies and population data of 12 Y-chromosome STR loci DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439 were determined from a sample of 150 unrelated male individuals from El Salvador, Central America. A total of 131 haplotypes were identified by the 12 Y-STR loci of which 118 were unique. The haplotype diversity (99.08%) and the proportion of different haplotypes (87.33%) were estimated. R(ST) genetic distances were calculated between El Salvador and other populations from Southern and Central America, Europe and Africa. The highest R(ST) genetic distances were found when comparing El Salvador with African populations (0.334
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The C-509T promoter polymorphism of the transforming growth factor beta-1 gene is associated with levels of total and specific IgE in a Colombian population.
Int. Arch. Allergy Immunol.
PUBLISHED: 05-29-2009
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The C-509T polymorphism of the transforming growth factor beta-1 (TGFB1) gene has been associated with asthma and asthma-related phenotypes, but its influence on total and specific IgE levels is controversial.
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Population stratification in Argentina strongly influences likelihood ratio estimates in paternity testing as revealed by a simulation-based approach.
Int. J. Legal Med.
PUBLISHED: 05-26-2009
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A simulation-based analysis was carried out to investigate the potential effects of population substructure in paternity testing in Argentina. The study was performed by evaluating paternity indexes (PI) calculated from different simulated pedigree scenarios and using 15 autosomal short tandem repeats (STRs) from eight Argentinean databases. The results show important statistically significant differences between PI values depending on the dataset employed. These differences are more dramatic when considering Native American versus urban populations. This study also indicates that the use of Fst to correct for the effect of population stratification on PI might be inappropriate because it cannot account for the particularities of single paternity cases.
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A Six-SNP haplotype of ADAM33 is associated with asthma in a population of Cartagena, Colombia.
Int. Arch. Allergy Immunol.
PUBLISHED: 04-22-2009
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A disintegrin and metalloprotein-33 (ADAM33) participates in the bronchial remodeling process in asthma, and genetic analyses pointed it out as a candidate gene in asthma.
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J1-M267 Y lineage marks climate-driven pre-historical human displacements.
Eur. J. Hum. Genet.
PUBLISHED: 04-15-2009
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The present day distribution of Y chromosomes bearing the haplogroup J1 M267(*)G variant has been associated with different episodes of human demographic history, the main one being the diffusion of Islam since the Early Middle Ages. To better understand the modes and timing of J1 dispersals, we reconstructed the genealogical relationships among 282 M267(*)G chromosomes from 29 populations typed at 20 YSTRs and 6 SNPs. Phylogenetic analyses depicted a new genetic background consistent with climate-driven demographic dynamics occurring during two key phases of human pre-history: (1) the spatial expansion of hunter gatherers in response to the end of the late Pleistocene cooling phases and (2) the displacement of groups of foragers/herders following the mid-Holocene rainfall retreats across the Sahara and Arabia. Furthermore, J1 STR motifs previously used to trace Arab or Jewish ancestries were shown unsuitable as diagnostic markers for ethnicity.
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Allele frequencies of 15 STRs in a representative sample of the Brazilian population.
Forensic Sci Int Genet
PUBLISHED: 03-26-2009
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Allele frequencies for 15 short tandem repeat (STR) loci were obtained from a sample of 12,030 individuals undergoing paternity testing. This sample includes individuals from all States in Brazil, combined according to the current country division into five regions (North, Northeast, Central West, Southeast, and South). The most polymorphic loci were D2S1338 and D18S51. All the analysed loci meet Hardy-Weinberg equilibrium expectations. Combined power of discrimination and combined power of exclusion for the 15 tested STR loci were 0.999999999999990 and 0.9999992, respectively. Comparative analysis between populations from different Brazilian macroregions as well as between Brazil and other relevant populations are presented.
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Genetic profiles and sex identification of found-dead wolves determined by the use of an 11-loci PCR multiplex.
Forensic Sci Int Genet
PUBLISHED: 03-16-2009
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A previously described canine-specific 9-STR multiplex, now including two markers for sex determination, was tested for the genotyping of 23 wolves from Northern and Central Portugal. The samples were collected at necropsies and presented varying states of preservation. Complete profiles were obtained in 74% of the samples, partial profiles in 22% and one completely null profile. This survey revealed 15 alleles not previously described in dogs, distributed among 6 STR loci. It is shown that this genotyping system, previously tested in domestic dogs, can be reliably used for obtaining complete genetic profiles in wolves with a matching probability of 2.45 x 10(-9) and compatible sex identification, even in sub-optimal samples. Moreover, a population structure analysis using the observed genotypes revealed that this multiplexed 11-loci panel may potentially be used for discriminating between wolves and dogs.
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Evaluation of DXS9902, DXS7132, DXS6809, DXS7133, and DXS7423 in humans and chimpanzees: sequence variation, repeat structure, and nomenclature.
Int. J. Legal Med.
PUBLISHED: 03-10-2009
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Sequencing data obtained in this study provide information on the short tandem repeat allele structures of DXS9902, DXS7132, DXS6809, DXS7133, and DXS7423. Data were obtained from the three human major population groups, namely Africans, Caucasians, and Asians as well as from chimpanzees (Pan troglodytes). DXS7133 was found to be the most stable locus and DXS6809 seemed to have evolved from a simple array of CTAT units but currently reveals a highly complex and compound structure within and between humans and chimpanzees. DXS9902 results support a TAGA allele nomenclature, which increases in one repeat unit previously reported allele distributions at this locus. For DXS7132, human/chimpanzee comparisons performed in this study provided important evidence that the CTAT allele structure should be considered for allele nomenclature purposes. Also, possible population-specific intermediate type alleles (with Native American origin) were detected at this locus that could be useful for ethnic group differentiation. DXS7423 results revealed two different sequence structures and one of these structures seems to be restricted to a single allele class in just one population group (Africans).
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Population data for 12 Y-chromosome STR loci in a sample from Honduras.
Leg Med (Tokyo)
PUBLISHED: 02-25-2009
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Haplotype, allele frequencies and population data of 12 Y-chromosome STR loci DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439 were determined from a sample of 128 unrelated male individuals from Honduras, Central America. A total of 112 haplotypes were identified by the 12 Y-STR loci of which 98 were unique. The haplotype diversity (98.99%) and the proportion of different haplotypes (87.50%) were estimated. Genetic distances were calculated between Honduras and other populations from Southern and Central America, Europe and Africa. The analysis of a Multi Dimensional Scaling (MDS) plot, based on pairwise R(ST) genetic distances, allowed to conclude that Honduras is highly differentiated from the African samples (0.343< or =R(ST)< or =0.620; P=0.000) and from a Native American sample from Argentina, Tobas (R(ST)=0.210, P=0.000). Honduras showed a lower genetic distance to the European cluster (composed by European and South American general population samples from Brazil, Argentina, Colombia and Venezuela) than to the Central American cluster (Mexico and El Salvador).
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The c.156_157insAlu BRCA2 rearrangement accounts for more than one-fourth of deleterious BRCA mutations in northern/central Portugal.
Breast Cancer Res. Treat.
PUBLISHED: 02-20-2009
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We evaluated the contribution of an Alu insertion in BRCA2 exon 3 (c.156_157insAlu) to inherited predisposition to breast/ovarian cancer in 208 families originated mostly from northern/central Portugal. We identified the c.156_157insAlu BRCA2 mutation in 14 families and showed that it accounts for more that one-fourth of deleterious BRCA1/BRCA2 mutations in breast/ovarian cancer families originated from this part of the country. This mutation originates BRCA2 exon 3 skipping and we demonstrated its pathogenic effect by showing that the BRCA2 full length transcript is derived only from the wild type allele in carriers, that it is absent in 262 chromosomes from healthy blood donors, and that it co-segregates with the disease. Polymorphic microsatellite markers were used for haplotype analysis in three informative families. In two of the three families one haplotype was shared for all but two markers, whereas in the third family all markers telomeric to BRCA2 differed from that observed in the other two. Although the c.156_157insAlu BRCA2 mutation has so far only been identified in Portuguese breast/ovarian cancer families, screening of this rearrangement in other populations will allow evaluation of whether or not it is a population-specific founder mutation and a more accurate estimation of its distribution and age.
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Quantification of epigenetic and genetic 2nd hits in CDH1 during hereditary diffuse gastric cancer syndrome progression.
Gastroenterology
PUBLISHED: 02-16-2009
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Hereditary diffuse gastric cancer (HDGC) families carry CDH1 heterozygous germline mutations; their tumors acquire complete CDH1 inactivation through "2nd-hit" mechanisms. Most frequently, this occurs via promoter hypermethylation (epigenetic modification), and less frequently via CDH1 mutations and loss of heterozygosity (LOH). We quantified the different 2nd hits in CDH1 occurring in neoplastic lesions from HDGC patients.
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Analysis of 10 X-linked tetranucleotide markers in mixed and isolated populations.
Forensic Sci Int Genet
PUBLISHED: 02-14-2009
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We have applied a recently described X-STRs decaplex to characterize four population groups of the Iberian Peninsula, including two well mixed populations and two relatively isolated ones from Northern Spain, in order to get a better insight about the characteristics of X-STRs in those population types between-population differences in allelic frequencies were relatively small. Nevertheless, Fst values were between 0.2 and 2.7%, figures higher than usually reported for autosomic STRs. This result suggests that when forensic cases originate from relatively isolated groups in western Europe, and a specific reference database is not available, it is probably safe to include a Fst-based correction in the calculations of matching or kinship probabilities.
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Population data defined by 15 autosomal STR loci in Karamoja population (Uganda) using AmpF/STR Identifiler kit.
Forensic Sci Int Genet
PUBLISHED: 02-14-2009
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Karamoja is a region located in the northeast edge of Uganda where it borders Kenya and Sudan. The majority of inhabitants of this region belong to Karimojong ethnic groups. In this work, we present allele frequencies for 15 STRs included in the AmpF/STR Identifiler kit (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPO and VWA) in 218 unrelated individuals from Karamoja region. Observed genotype distributions for each locus do not show deviations from Hardy-Weinberg equilibrium expectations. When comparing allele frequencies, for each locus, with other five African samples (Equatorial Guinea, Mozambique, Cabinda (Angola), Rwanda and Tanzania) the only population that did not show significant differences with Karamoja (Uganda) was Rwanda.
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Distribution of Y-chromosomal haplotypes in the Central Portuguese population using 17-STRs.
Forensic Sci Int Genet
PUBLISHED: 02-11-2009
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17 Y-chromosome STR loci (DYS19, DYS389I, DYS389II, DYS390, DYS456, DYS391, DYS392, DYS393, DYS385 a/b, DYS458, DYS439, DYS635, GATA H4.1, DYS437, DYS438 and DYS448) were determined for 303 unrelated males, living in Central Portugal, using the AmpFlSTR YFiler PCR Amplification kit (Applied Biosystems). A total of 287 different haplotypes were found, 272 being unique. The overall haplotype diversity (HD) was determined as 0.9996, a value similar to other YFiler data sets. Y-STR polymorphisms in Central Portugal population, using YFiler, provide a powerful discrimination tool for routine forensic applications.
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A new autosomal STR nineplex for canine identification and parentage testing.
Electrophoresis
PUBLISHED: 02-11-2009
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A single multiplex PCR assay capable of simultaneously amplifying nine canine-specific autosomal STR markers (FH3210, FH3241, FH2004, FH2658, FH4012, REN214L11, FH2010, FH2361 and the newly described C38) was developed for individual identification and parentage testing in domestic dogs. In order to increase genotyping efficiency, amplicon sizes were optimized for a 90-350 bp range, with fluorescently labelled primers for use in Applied Biosystems, Inc., platforms. The performance of this new multiplex system was tested in 113 individuals from a case-study population and 12 random dogs from mixed-breed origin. Co-dominant inheritance of STR alleles was investigated in 101 father, mother and son trios. Expected heterozygosity values vary between 0.5648 for REN214L11 and 0.9050 for C38. The high level of genetic diversity observed for most markers provides this multiplex with a very high discriminating power (matching probability=1.63/10(10) and matching probability among siblings=4.9/10(3)). Allele sequences and a proposal for standardized nomenclature are also herein presented, aiming at implementing the use of this system in forensic DNA typing and population genetic studies. This approach resulted in an optimized and well-characterized canine DNA genotyping system that is highly performing and straightforward to integrate and employ routinely. Although this STR multiplex was developed for use and tested in a case-study population, the Portuguese breed Cão de Gado Transmontano, it proved to be useful for general identification purposes or parentage testing.
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Moors and Saracens in Europe: estimating the medieval North African male legacy in southern Europe.
Eur. J. Hum. Genet.
PUBLISHED: 01-21-2009
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To investigate the male genetic legacy of the Arab rule in southern Europe during medieval times, we focused on specific Northwest African haplogroups and identified evolutionary close STR-defined haplotypes in Iberia, Sicily and the Italian peninsula. Our results point to a higher recent Northwest African contribution in Iberia and Sicily in agreement with historical data. southern Italian regions known to have experienced long-term Arab presence also show an enrichment of Northwest African types. The forensic and genomic implications of these findings are discussed.
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Demographic history of Canary Islands male gene-pool: replacement of native lineages by European.
BMC Evol. Biol.
PUBLISHED: 01-16-2009
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The origin and prevalence of the prehispanic settlers of the Canary Islands has attracted great multidisciplinary interest. However, direct ancient DNA genetic studies on indigenous and historical 17th-18th century remains, using mitochondrial DNA as a female marker, have only recently been possible. In the present work, the analysis of Y-chromosome polymorphisms in the same samples, has shed light on the way the European colonization affected male and female Canary Island indigenous genetic pools, from the conquest to present-day times.
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Reconstructing the population history of European Romani from genome-wide data.
Curr. Biol.
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The Romani, the largest European minority group with approximately 11 million people, constitute a mosaic of languages, religions, and lifestyles while sharing a distinct social heritage. Linguistic and genetic studies have located the Romani origins in the Indian subcontinent. However, a genome-wide perspective on Romani origins and population substructure, as well as a detailed reconstruction of their demographic history, has yet to be provided. Our analyses based on genome-wide data from 13 Romani groups collected across Europe suggest that the Romani diaspora constitutes a single initial founder population that originated in north/northwestern India ~1.5 thousand years ago (kya). Our results further indicate that after a rapid migration with moderate gene flow from the Near or Middle East, the European spread of the Romani people was via the Balkans starting ~0.9 kya. The strong population substructure and high levels of homozygosity we found in the European Romani are in line with genetic isolation as well as differential gene flow in time and space with non-Romani Europeans. Overall, our genome-wide study sheds new light on the origins and demographic history of European Romani.
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Analysis of genetic ancestry in the admixed Brazilian population from Rio de Janeiro using 46 autosomal ancestry-informative indel markers.
Ann. Hum. Biol.
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The Brazilian population is highly heterogeneous as a result of five centuries of inter-ethnic mating between native Amerindians, European colonizers and Africans arrived during slavery. This study aimed to assess the proportions of inter-ethnic admixture in the Brazilian population of Rio de Janeiro using autosomal Ancestry-Informative Markers (AIMs). The autosomal data were also compared to the results expected from uniparental genetic markers. A total of 413 individuals were genotyped for 46 AIM-Indels and ancestry estimates were then assessed using HGDP-CEPH samples as ancestral reference. Individuals from Rio de Janeiro presented highly diverse admixture patterns. The global admixture estimates showed a predominantly European ancestry, above 55%, followed by African and Amerindian contributions. A separate self-declared Afro-descendant group also included in this study revealed an increased African ancestry, from ?30% to ?50%. The inter-ethnic admixture landscape of Rio de Janeiro captured by autosomal AIM-Indels is in agreement with historical records and similar to that expected from uniparental mtDNA and Y-chromosome information. The AIM-Indel panel proved to be a rapid strategy to estimate autosomal genetic ancestry at individual and population levels in Rio de Janeiro, which is useful in population genetics and in case-control association studies.
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Comparative evaluation of alternative batteries of genetic markers to complement autosomal STRs in kinship investigations: autosomal indels vs. X-chromosome STRs.
Int. J. Legal Med.
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Kinship investigations such as paternity are currently solved using sets of (commercially available) highly polymorphic autosomal short tandem repeats (STRs), which lead to powerful likelihood ratios (LR). Still, some difficult cases arise whenever the kinship is much more remote or if the alternative hypotheses are not correctly formulated due to the lack of information (for e.g. there is an unknown relationship between the alleged and the true fathers). In these situations, beyond the routinely used marker set, laboratories usually enlarge the number and/or the type of markers analysed. Among these, autosomal indels and X-chromosome STRs have gained popularity. The aim of this study was to compare the results obtained after complementing an initial set of autosomal STRs with indels or with X-chromosome-specific STRs in simulated paternity cases where the alleged father is a close relative of the real one. Results show that in paternity cases where a low number of incompatibilities are observed, the best strategy is to increase the number of autosomal STRs under analysis. Nevertheless, if these are not available, our study globally shows that in father-daughter duos, a set of 12 X-STRs is more advantageous than 38 highly diverse autosomal biallelic markers. Additionally, the usefulness of X-STRs was also evaluated in cases where only a close relative of the alleged parent (father or mother) is available for testing. For those situations where these markers have the power to exclude, strong LR values are obtained. In the remaining cases, LRs are usually weak and sometimes the results are more likely under the wrong kinship hypothesis.
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The genetic landscape of Equatorial Guinea and the origin and migration routes of the Y chromosome haplogroup R-V88.
Eur. J. Hum. Genet.
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Human Y chromosomes belonging to the haplogroup R1b1-P25, although very common in Europe, are usually rare in Africa. However, recently published studies have reported high frequencies of this haplogroup in the central-western region of the African continent and proposed that this represents a back-to-Africa migration during prehistoric times. To obtain a deeper insight into the history of these lineages, we characterised the paternal genetic background of a population in Equatorial Guinea, a Central-West African country located near the region in which the highest frequencies of the R1b1 haplogroup in Africa have been found to date. In our sample, the large majority (78.6%) of the sequences belong to subclades in haplogroup E, which are the most frequent in Bantu groups. However, the frequency of the R1b1 haplogroup in our sample (17.0%) was higher than that previously observed for the majority of the African continent. Of these R1b1 samples, nine are defined by the V88 marker, which was recently discovered in Africa. As high microsatellite variance was found inside this haplogroup in Central-West Africa and a decrease in this variance was observed towards Northeast Africa, our findings do not support the previously hypothesised movement of Chadic-speaking people from the North across the Sahara as the explanation for these R1b1 lineages in Central-West Africa. The present findings are also compatible with an origin of the V88-derived allele in the Central-West Africa, and its presence in North Africa may be better explained as the result of a migration from the south during the mid-Holocene.
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Diversity and specificity of microsatellites within Aspergillus section Fumigati.
BMC Microbiol.
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Microsatellites (or short tandem repeats, STRs) are the genetic markers of choice for studying Aspergillus fumigatus molecular epidemiology due to its reproducibility and high discrimination power. However, the specificity of these markers must be investigated in a group of isolates from closely related species. The aim of this work was to test a microsatellite-based PCR multiplex previously designed for A. fumigatus in a set of species belonging to section Fumigati, namely Aspergillus fumigatiaffinis, Aspergillus lentulus, Aspergillus novofumigatus, Aspergillus unilateralis, Aspergillus viridinutans, Neosartorya fischeri, Neosartorya hiratsukae, Neosartorya pseudofischeri and Neosartorya udagawae.
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Genetic profile characterization of ten X-STRs in a sample from Paraná, Brazil.
Int. J. Legal Med.
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This work reports the allele frequencies for ten X-STRs (DXS8378, DXS7132, DXS9898, DXS6809, DXS9902, DXS6789, DXS7133, DXS7423, GATA172D05, GATA31E08) in a sample of 800 individuals from Paraná, Brazil. No deviations from the Hardy-Weinberg equilibrium were observed. Linkage disequilibrium analysis did not reveal association between the X-STRs. High overall power of discrimination was obtained for female and male samples, and high probability of exclusion was observed in father/mother/daughter trios and father/daughter duos. Genetic comparisons revealed significant differences between Paraná and other Brazilian populations.
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Disclosing the genetic structure of Brazil through analysis of male lineages with highly discriminating haplotypes.
PLoS ONE
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In a large variety of genetic studies, probabilistic inferences are made based on information available in population databases. The accuracy of the estimates based on population samples are highly dependent on the number of chromosomes being analyzed as well as the correct representation of the reference population. For frequency calculations the size of a database is especially critical for haploid markers, and for countries with complex admixture histories it is important to assess possible substructure effects that can influence the coverage of the database. Aiming to establish a representative Brazilian population database for haplotypes based on 23 Y chromosome STRs, more than 2,500 Y chromosomes belonging to Brazilian, European and African populations were analyzed. No matter the differences in the colonization history of the five geopolitical regions that currently exist in Brazil, for the Y chromosome haplotypes of the 23 studied Y-STRs, a lack of genetic heterogeneity was found, together with a predominance of European male lineages in all regions of the country. Therefore, if we do not consider the diverse Native American or Afro-descendent isolates, which are spread through the country, a single Y chromosome haplotype frequency database will adequately represent the urban populations in Brazil. In comparison to the most commonly studied group of 17 Y-STRs, the 23 markers included in this work allowed a high discrimination capacity between haplotypes from non-related individuals within a population and also increased the capacity to discriminate between paternal relatives. Nevertheless, the expected haplotype mutation rate is still not enough to distinguish the Y chromosome profiles of paternally related individuals. Indeed, even for rapidly mutating Y-STRs, a very large number of markers will be necessary to differentiate male lineages from paternal relatives.
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Assessing paternities with inconclusive STR results: The suitability of bi-allelic markers.
Forensic Sci Int Genet
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In paternity testing the genetic profiles of the individuals are used to compare the relative likelihoods of the alleged father and the child being related as father/offspring against, usually, being unrelated. In the great majority of the cases, analyses with the widely used sets of short tandem repeat markers (STRs) provide powerful statistical evidence favouring one of the alternative hypotheses. Nevertheless, there are situations where the final statistical result is ambiguous, mostly because the alleged father shows incompatible genotypes at a few loci along with a very high paternity index in the remaining systems. In these cases, the possibility that the alleged father is actually a close relative of the real one (son, father or brother) can reasonably be raised. In such cases, when the statistical evidence obtained is considered as insufficient, the common practice is to extend the set of analysed markers. In this context, many authors have suggested that bi-allelic markers, such as single nucleotide (SNP) or insertion/deletion (Indel) polymorphisms, are markers of choice, as they are incomparably less prone to mutation than STRs. In this work we address the soundness of this claim and the consequences of this strategy, analyzing the a priori odds both for (a) expected number of Mendelian incompatibilities, and (b) expected values for the final likelihood ratios. Moreover, one hundred real pairs of second degree relatives, typed for two sets of markers: 15 STRs plus 38 Indels, were used to simulate paternity testing. Our data show that, for the number of markers commonly considered, the results from an extended battery of SNPs or Indels should be interpreted with caution when relatives are possibly involved.
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