Effects of Plasma from Bivalve Mollusk Species on the in Vitro Proliferation of the Protistan Parasite Perkinsus Marinus

The Journal of Experimental Zoology. Feb, 2002  |  Pubmed ID: 11857456

The in vitro culture of the Eastern oyster parasite Perkinsus marinus has provided a unique opportunity to examine its susceptibility to putative recognition and effector defense mechanisms operative in refractory bivalve species. In this study, we report the effect of supplementing the culture medium with plasma from: (1) uninfected to heavily infected Eastern oysters; (2) oyster species considered to be disease-resistant; and (3) bivalve mollusk species that are naturally exposed to the parasite but show no signs of disease. We also examined in vitro the interaction between hemocytes from Crassostrea virginica and C. gigas and P. marinus trophozoites. Our results revealed a significant decrease (32%) in proliferation of P. marinus in the presence of plasma from heavily infected C. virginica oysters. The inhibitory effects were less pronounced with plasma from moderately infected and uninfected oysters. In contrast, plasma from C. rivularis and C. gigas enhanced P. marinus proliferation. Proliferation was significantly reduced in media supplemented with plasma from Mytilus edulis, Mercenaria mercenaria, and Anadara ovalis. The highest inhibitory activity was apparent in M. edulis, for which 5% plasma-supplemented medium reduced growth by 35% relative to the controls. M. edulis active component(s) was heat-stable, yet pronase-sensitive. The significantly higher uptake of live P. marinus trophozoites by hemocytes from C. virginica, relative to those from C. gigas, suggests a certain level of specificity in the recognition/endocytosis of the parasite by its natural bivalve host species.

Nucleotide Sequence of the P53 CDNA of Beluga Whale (Delphinapterus Leucas)

Gene. Apr, 2002  |  Pubmed ID: 12034505

The cDNA (DNA complementary to RNA) of the p53 gene of the beluga whale (Delphinapterus leucas) was sequenced by the method of 5'- and 3'-rapid amplification of cDNA ends (RACE) with the cDNA made for the RNA obtained from fresh peripheral blood leukocytes isolated from two animals. Primers for the RACE method were synthesized based on the sequence of the DNA of beluga whale corresponding to exon 5 of the human p53 gene, which was determined after amplification of the DNA isolated from the liver from a beluga whale by using a pair of primers for the human sequence. The sequenced cDNA had a 2150-nucleotide length and contained the whole region corresponding to human exons 1 through 11. The reading frame was 1164 bp (base pair) long and began in exon 2 and ended in exon 11, coding for a 387-amino acid protein. The nucleotide sequence of the reading frame showed high similarity over 85% with pig, sheep, cow, and human genes. The similarities with the former two animals at the amino acid level were also more than 85%. Lower similarity of the beluga whale p53 gene was also found with those of lower tetrapods, fish and invertebrates.

Catechol-O-methyltransferase Val-108/158-Met Gene Variants Associated with Performance on the Wisconsin Card Sorting Test

Archives of General Psychiatry. Jul, 2002  |  Pubmed ID: 12090821

CDNA Cloning and Characterization of Two Iron Superoxide Dismutases from the Oyster Parasite Perkinsus Marinus

Molecular and Biochemical Parasitology. Aug, 2002  |  Pubmed ID: 12165391

Mutation Screening of FOXP2 in Individuals Diagnosed with Autistic Disorder

American Journal of Medical Genetics. Part A. Apr, 2003  |  Pubmed ID: 12655497

Although it is well established that genetic factors play an important role in the etiology of autistic disorder (AD), no specific genes have as yet been implicated. Genetic epidemiological data, particularly the sharp fall in concordance rates from monozygotic to dizygotic twins, indicate that the mode of transmission of this disorder is complex and may involve several genes. The 7q31 locus has been repeatedly linked to AD, suggesting that this chromosomal region is likely to harbor a susceptibility gene for AD. Recently, variations in the FOXP2 gene were reported to be responsible for a severe speech and language disorder. Because of the chromosomal location of FOXP2 (7q31) and the putative implication of the 7q31 region both in autistic and in language disorders (a feature of AD), it has been hypothesized that FOXP2 may be implicated in the pathophysiology of AD. To test this hypothesis, we screened the FOXP2 gene coding sequence for mutations in subjects diagnosed with AD and in normal controls. We identified four silent polymorphisms that were equally distributed between patients and controls. Using an intra-family association design, we identified no transmission disequilibrium in any of the four identified alleles, suggesting that the FOXP2 gene does not play a significant role in AD.

Superoxide Dismutases from the Oyster Parasite Perkinsus Marinus: Purification, Biochemical Characterization, and Development of a Plate Microassay for Activity

Analytical Biochemistry. Jul, 2003  |  Pubmed ID: 12782041

We have isolated and biochemically characterized superoxide dismutase (SOD) activity in cell extracts of clonally cultured Perkinsus marinus, a facultative intracellular parasite of the Eastern oyster, Crassostrea virginica. In order to assess the SOD activity throughout the purification, we developed and optimized a 96-well-plate microassay based on the inhibition of pyrogallol oxidation. The assay was also adapted to identify SOD activity type (Cu/Zn-, Mn-, or FeSOD), even in mixtures of more than one type of SOD. All SOD activity detected in the cell extracts was of the FeSOD type. Most of the SOD activity in P. marinus trophozoites resides in a major component of subunit molecular weight 24 kDa. The protein was purified by affinity chromatography on an anti-SOD antibody-Sepharose column. Amino-terminal peptide sequence of the affinity-purified protein corresponds to the predicted product of the PmSOD1 gene and indicates that amino-terminal processing has taken place. The results are discussed in the context of processing of mitochondrially targeted SODs.

A Serosurvey of Leptospirosis in Connecticut Peridomestic Wildlife

Vector Borne and Zoonotic Diseases (Larchmont, N.Y.). 2003  |  Pubmed ID: 14733671

Recently, leptospirosis has gained attention as a re-emerging infection in domestic dogs in the northeastern United States. In order to gain insight into the epizootiology of leptospirosis in this region, 109 small wild mammals (31 raccoons (Procyon lotor), 30 skunks (Mephitis mephitis), 28 opossums (Didelphis virginiana), and 20 gray squirrels (Sciurus carolinensis)) collected between February 27 and September 17, 2001 were tested for serologic evidence of exposure to five common Leptospira serovars (serovars pomona, icterohemorrhagiae, canicola, hardjo, grippotyphosa). Evidence of exposure to leptospirosis was detected in 36% of raccoons tested; icterohemorrhagiae was the predominant reactive serovar in these animals. Sera from 13% of skunks showed evidence of exposure to serovar grippotyphosa. One squirrel exhibited high antibody titers to serovars grippotyphosa and canicola. All 28 opossums examined tested negative to the five Leptospira serovars. Results from this serosurvey suggest that common peridomestic wildlife species should be considered as potential sources of leptospirosis to dogs and humans in Connecticut. Additional investigation is warranted to clarify their role in the epidemiology of this zoonotic disease in the northeastern United States.

Flow Cytometric Analysis of Lectin Binding to in Vitro-cultured Perkinsus Marinus Surface Carbohydrates

The Journal of Parasitology. Jun, 2004  |  Pubmed ID: 15270084

Parasite surface glycoconjugates are frequently involved in cellular recognition and colonization of the host. This study reports on the identification of Perkinsus marinus surface carbohydrates by flow cytometric analyses of fluorescein isothiocyanate-conjugated lectin binding. Lectin-binding specificity was confirmed by sugar inhibition and Kolmogorov-Smirnov statistics. Clear, measurable fluorescence peaks were discriminated, and no parasite autofluorescence was observed. Parasites (GTLA-5 and Perkinsus-1 strains) harvested during log and stationary phases of growth in a protein-free medium reacted strongly with concanavalin A and wheat germ agglutinin, which bind to glucose-mannose and N-acetyl-D-glucosamine (GlcNAc) moieties, respectively. Both P. marinus strains bound with lower intensity to Maclura pomifera agglutinin, Bauhinia purpurea agglutinin, soybean agglutinin (N-acetyl-D-galactosamine-specific lectins), peanut agglutinin (PNA) (terminal galactose specific), and Griffonia simplicifolia II (GlcNAc specific). Only background fluorescence levels were detected with Ulex europaeus agglutinin I (L-fucose specific) and Limulus polyphemus agglutinin (sialic acid specific). The lectin-binding profiles were similar for the 2 strains except for a greater relative binding intensity of PNA for Perkinsus-1 and an overall greater lectin-binding capacity of Perkinsus-1 compared with GTLA-5. Growth stage comparisons revealed increased lectin-binding intensities during stationary phase compared with log phase of growth. This is the first report of the identification of surface glycoconjugates on a Perkinsus spp. by flow cytometry and the first to demonstrate that differential surface sugar expression is growth phase and strain dependent.

NLGN3/NLGN4 Gene Mutations Are Not Responsible for Autism in the Quebec Population

American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics : the Official Publication of the International Society of Psychiatric Genetics. Jan, 2005  |  Pubmed ID: 15389766

Jamain [2003: Nat Genet 34:27-29] recently reported mutations in two neuroligin genes in sib-pairs affected with autism. In order to confirm these causative mutations in our autistic population and to determine their frequency we screened 96 individuals affected with autism. We found no mutations in these X-linked genes. These results indicate that mutations in NLGN3 and NLGN4 genes are responsible for at most a small fraction of autism cases and additional screenings in other autistic populations are needed to better determine the frequency with which mutations in NLGN3 and NLGN4 occur in autism.

Capillary Electrophoresis Separation of a Mixture of Chitin and Chitosan Oligosaccharides Derivatized Using a Modified Fluorophore Conjugation Procedure

Journal of Separation Science. Aug, 2005  |  Pubmed ID: 16138691

A capillary electrophoresis (CE) method was developed for the simultaneous analysis of small chitin and chitosan oligosaccharides. For detection purposes, the oligomers were derivatized with 8-aminopyrene-1,3,6-trisulfonic acid (APTS), a well known fluorophore for oligosaccharides analysis. The detection was performed by laser-induced fluorescence (LIF) with an argon ion laser having an excitation wavelength of 488 nm and with emission monitored at 520 nm. Derivatization parameters such as reaction time and conditions were examined. Separation conditions were also varied by testing a range of buffer pHs and concentrations. The best conditions were found using an 80 mM borate buffer at pH 8.4. This CE-LIF optimized method was used for the analysis of an enzymatically produced oligo-chitosan sample composed of a complex mixture and having an average degree of polymerization of 3.7 monomer units and 80% deacetylation. The oligo-chitosan sample was treated with a chitin deacetylase-like enzyme, the products were derivatized with APTS, and then analyzed without purification. The goal was to determine whether the deacetylase-like enzyme could increase the extent of deacetylation of the oligo-chitosan sample.

Clinical Stringency Greatly Improves Mutation Detection in Rett Syndrome

The Canadian Journal of Neurological Sciences. Le Journal Canadien Des Sciences Neurologiques. Aug, 2005  |  Pubmed ID: 16225173

Rett syndrome (RTT) is a severe neurodevelopmental disorder of girls, caused by mutations in the X-linked MECP2 gene. Worldwide recognition of the RTT clinical phenotype in the early 1980's allowed many cases to be diagnosed, and established RTT as one of the most common mental retardation syndromes in females. The years since then led to a refinement of the phenotype and the recent elaboration of Revised Diagnostic Criteria (RDC). Here, we study the impact of the presence versus the absence of the use of diagnostic criteria from the RDC to make a diagnosis of RTT on MECP2 mutation detection in Canadian patients diagnosed and suspected of having RTT.

Sleep and COMT Polymorphism in ADHD Children: Preliminary Actigraphic Data

Journal of the American Academy of Child and Adolescent Psychiatry. Aug, 2006  |  Pubmed ID: 16865041

To examine whether COMT (catechol-O-methyltransferase) polymorphism modulates aspects of sleep in children diagnosed with attention-deficit/hyperactivity disorder (ADHD).

Transmission Disequilibrium Study of an Oligodendrocyte and Myelin Glycoprotein Gene Allele in 431 Families with an Autistic Proband

Neuroscience Research. Dec, 2007  |  Pubmed ID: 17897745

Autistic disorder is a neurodevelopmental disorder where genetic factors play an important role. We previously described an association between a subgroup of French autistic patients and an allele of a non-synonymous single nucleotide polymorphism (nsSNP: OMGP62 G>A or rs11080149) in the gene coding for the oligodendrocyte and myelin glycoprotein (OMG), located at 7Mb from the marker D17S250, linked to autism in two independent genome scan studies. We report a study on 431 families with 1 affected child from different origins: French Canada (n=262), Italy (n=123) and United States (n=46). We analyzed the transmission of the rs11080149 alleles from parents to their affected children. There was a preferential transmission of the G allele from parents to affected children (p=0.0017) in the overall sample. Paternal and maternal transmission rates were both skewed. Taking into account our previous results obtained in a French group of patients, where we observed an association with allele A, a direct role of this polymorphism is improbable in autism. The associations observed in Japanese and French patients, the linkage studies and the present work speak in favor of the existence of a susceptibility gene for autism in the NF1 locus.

Mutations in the Calcium-related Gene IL1RAPL1 Are Associated with Autism

Human Molecular Genetics. Dec, 2008  |  Pubmed ID: 18801879

In a systematic sequencing screen of synaptic genes on the X chromosome, we have identified an autistic female without mental retardation (MR) who carries a de novo frameshift Ile367SerfsX6 mutation in Interleukin-1 Receptor Accessory Protein-Like 1 (IL1RAPL1), a gene implicated in calcium-regulated vesicle release and dendrite differentiation. We showed that the function of the resulting truncated IL1RAPL1 protein is severely altered in hippocampal neurons, by measuring its effect on neurite outgrowth activity. We also sequenced the coding region of the close related member IL1RAPL2 and of NCS-1/FREQ, which physically interacts with IL1RAPL1, in a cohort of subjects with autism. The screening failed to identify non-synonymous variant in IL1RAPL2, whereas a rare missense (R102Q) in NCS-1/FREQ was identified in one autistic patient. Furthermore, we identified by comparative genomic hybridization a large intragenic deletion of exons 3-7 of IL1RAPL1 in three brothers with autism and/or MR. This deletion causes a frameshift and the introduction of a premature stop codon, Ala28GlufsX15, at the very beginning of the protein. All together, our results indicate that mutations in IL1RAPL1 cause a spectrum of neurological impairments ranging from MR to high functioning autism.

Identification of Drostanolone and 17-methyldrostanolone Metabolites Produced by Cryopreserved Human Hepatocytes

Steroids. Mar, 2009  |  Pubmed ID: 19056412

Methyldrostanolone (2alpha,17alpha-dimethyl-17beta-hydroxy-5alpha-androstan-3-one) was synthesized from drostanolone (17beta-hydroxy-2alpha-methyl-5alpha-androstan-3-one) and identified in commercial products. Cultures of cryopreserved human hepatocytes were used to study the biotransformation of drostanolone and its 17-methylated derivative. For both steroids, the common 3alpha- (major) and 3beta-reduced metabolites were identified by GC-MS analysis of the extracted culture medium and the stereochemistry confirmed by incubation with 3alpha-hydroxysteroid dehydrogenase. Structures corresponding to hydroxylated metabolites in C-12 (minor) and C-16 were proposed for other metabolites based upon the evaluation of the mass spectra of the pertrimethylsilyl (TMS-d(0) and TMS-d(9)) derivatives. Finally, on the basis of the GC-MS and (1)H NMR data and through chemical synthesis of the 17-methylated model compounds, structures could be proposed for metabolites hydroxylated in C-2. All the metabolites extracted from hepatocyte culture medium were present although in different relative amounts in urines collected following the administration to a human volunteer, therefore confirming the suitability of the cryopreserved hepatocytes to generate characteristic metabolites and study biotransformation of new steroids.

Mutations in SYNGAP1 in Autosomal Nonsyndromic Mental Retardation

The New England Journal of Medicine. Feb, 2009  |  Pubmed ID: 19196676

Although autosomal forms of nonsyndromic mental retardation account for the majority of cases of mental retardation, the genes that are involved remain largely unknown. We sequenced the autosomal gene SYNGAP1, which encodes a ras GTPase-activating protein that is critical for cognition and synapse function, in 94 patients with nonsyndromic mental retardation. We identified de novo truncating mutations (K138X, R579X, and L813RfsX22) in three of these patients. In contrast, we observed no de novo or truncating mutations in SYNGAP1 in samples from 142 subjects with autism spectrum disorders, 143 subjects with schizophrenia, and 190 control subjects. These results indicate that SYNGAP1 disruption is a cause of autosomal dominant nonsyndromic mental retardation.

No Association Between SRGAP3/MEGAP Haploinsufficiency and Mental Retardation

Archives of Neurology. May, 2009  |  Pubmed ID: 19433673

Novel De Novo SHANK3 Mutation in Autistic Patients

American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics : the Official Publication of the International Society of Psychiatric Genetics. Apr, 2009  |  Pubmed ID: 18615476

A number of studies have confirmed that genetic factors play an important role in autism spectrum disorder (ASD). More recently de novo mutations in the SHANK3 gene, a synaptic scaffolding protein, have been associated with the ASD phenotype. As part of our gene discovery strategy, we sequenced the SHANK3 gene in a cohort of 427 ASD subjects and 190 controls. Here, we report the identification of two putative causative mutations: one being a de novo deletion at an intronic donor splice site and one missense transmitted from an epileptic father. We were able to confirm the deleterious effect of the splice site deletion by RT-PCR using mRNA extracted from cultured lymphoblastoid cells. The missense mutation, a leucine to proline at amino acid position 68, is perfectly conserved across all species examined, and would be predicted to disrupt an alpha-helical domain. These results further support the role of SHANK3 gene disruption in the etiology of ASD.

De Novo STXBP1 Mutations in Mental Retardation and Nonsyndromic Epilepsy

Annals of Neurology. Jun, 2009  |  Pubmed ID: 19557857

We sequenced genes coding for components of the SNARE complex (STX1A, VAMP2, SNAP25) and their regulatory proteins (STXBP1/Munc18-1, SYT1), which are essential for neurotransmission, in 95 patients with idiopathic mental retardation. We identified de novo mutations in STXBP1 (nonsense, p.R388X; splicing, c.169+1G>A) in two patients with severe mental retardation and nonsyndromic epilepsy. Reverse transcriptase polymerase chain reaction and sequencing showed that the splicing mutation creates a stop codon downstream of exon-3. No de novo or deleterious mutations in STXBP1 were found in 190 control subjects, or in 142 autistic patients. These results suggest that STXBP1 disruption is associated with autosomal dominant mental retardation and nonsyndromic epilepsy.

[De Novo Mutations in SYNGAP1 Associated with Non-syndromic Mental Retardation]

Médecine Sciences : M/S. Feb, 2010  |  Pubmed ID: 20188038

De Novo Mutations in the Gene Encoding the Synaptic Scaffolding Protein SHANK3 in Patients Ascertained for Schizophrenia

Proceedings of the National Academy of Sciences of the United States of America. Apr, 2010  |  Pubmed ID: 20385823

Schizophrenia likely results from poorly understood genetic and environmental factors. We studied the gene encoding the synaptic protein SHANK3 in 285 controls and 185 schizophrenia patients with unaffected parents. Two de novo mutations (R1117X and R536W) were identified in two families, one being found in three affected brothers, suggesting germline mosaicism. Zebrafish and rat hippocampal neuron assays revealed behavior and differentiation defects resulting from the R1117X mutant. As mutations in SHANK3 were previously reported in autism, the occurrence of SHANK3 mutations in subjects with a schizophrenia phenotype suggests a molecular genetic link between these two neurodevelopmental disorders.

De Novo Truncating Mutation in Kinesin 17 Associated with Schizophrenia

Biological Psychiatry. Oct, 2010  |  Pubmed ID: 20646681

Schizophrenia (SCZ) is one of the most disabling psychiatric disorders. It is thought to be due to a complex interplay between polygenic and various environmental risk factors, although recent reports on genomic copy number variations suggest that a fraction of the cases could result from variably penetrant de novo variants. The gene encoding the synaptic motor protein kinesin 17 (KIF17) involved in glutamatergic synapse is a candidate gene for SCZ.

Direct Measure of the De Novo Mutation Rate in Autism and Schizophrenia Cohorts

American Journal of Human Genetics. Sep, 2010  |  Pubmed ID: 20797689

The role of de novo mutations (DNMs) in common diseases remains largely unknown. Nonetheless, the rate of de novo deleterious mutations and the strength of selection against de novo mutations are critical to understanding the genetic architecture of a disease. Discovery of high-impact DNMs requires substantial high-resolution interrogation of partial or complete genomes of families via resequencing. We hypothesized that deleterious DNMs may play a role in cases of autism spectrum disorders (ASD) and schizophrenia (SCZ), two etiologically heterogeneous disorders with significantly reduced reproductive fitness. We present a direct measure of the de novo mutation rate (μ) and selective constraints from DNMs estimated from a deep resequencing data set generated from a large cohort of ASD and SCZ cases (n = 285) and population control individuals (n = 285) with available parental DNA. A survey of ∼430 Mb of DNA from 401 synapse-expressed genes across all cases and 25 Mb of DNA in controls found 28 candidate DNMs, 13 of which were cell line artifacts. Our calculated direct neutral mutation rate (1.36 × 10(-8)) is similar to previous indirect estimates, but we observed a significant excess of potentially deleterious DNMs in ASD and SCZ individuals. Our results emphasize the importance of DNMs as genetic mechanisms in ASD and SCZ and the limitations of using DNA from archived cell lines to identify functional variants.

Role of GacA in Virulence of Vibrio Vulnificus

Microbiology (Reading, England). Dec, 2010  |  Pubmed ID: 20817642

The GacS/GacA two-component signal transduction system regulates virulence, biofilm formation and symbiosis in Vibrio species. The present study investigated this regulatory pathway in Vibrio vulnificus, a human pathogen that causes life-threatening disease associated with the consumption of raw oysters and wound infections. Small non-coding RNAs (csrB1, csrB2, csrB3 and csrC) commonly regulated by the GacS/GacA pathway were decreased (P<0.0003) in a V. vulnificus CMCP6 ΔgacA : : aph mutant compared with the wild-type parent, and expression was restored by complementation of the gacA deletion mutation in trans. Of the 20 genes examined by RT-PCR, significant reductions in the transcript levels of the mutant in comparison with the wild-type strain were observed only for genes related to motility (flaA), stationary phase (rpoS) and protease (vvpE) (P=0.04, 0.01 and 0.002, respectively). Swimming motility, flagellation and opaque colony morphology indicative of capsular polysaccharide (CPS) were unchanged in the mutant, while cytotoxicity, protease activity, CPS phase variation and the ability to acquire iron were decreased compared with the wild-type (P<0.01). The role of gacA in virulence of V. vulnificus was also demonstrated by significant impairment in the ability of the mutant strain to cause either skin (P<0.0005) or systemic infections (P<0.02) in subcutaneously inoculated, non-iron-treated mice. However, the virulence of the mutant was equivalent to that of the wild-type in iron-treated mice, demonstrating that the GacA pathway in V. vulnificus regulates the virulence of this organism in an iron-dependent manner.

Disruption at the PTCHD1 Locus on Xp22.11 in Autism Spectrum Disorder and Intellectual Disability

Science Translational Medicine. Sep, 2010  |  Pubmed ID: 20844286

Autism is a common neurodevelopmental disorder with a complex mode of inheritance. It is one of the most highly heritable of the complex disorders, although the underlying genetic factors remain largely unknown. Here, we report mutations in the X-chromosome PTCHD1 (patched-related) gene in seven families with autism spectrum disorder (ASD) and in three families with intellectual disability. A 167-kilobase microdeletion spanning exon 1 was found in two brothers, one with ASD and the other with a learning disability and ASD features; a 90-kilobase microdeletion spanning the entire gene was found in three males with intellectual disability in a second family. In 900 probands with ASD and 208 male probands with intellectual disability, we identified seven different missense changes (in eight male probands) that were inherited from unaffected mothers and not found in controls. Two of the ASD individuals with missense changes also carried a de novo deletion at another ASD susceptibility locus (DPYD and DPP6), suggesting complex genetic contributions. In additional males with ASD, we identified deletions in the 5' flanking region of PTCHD1 that disrupted a complex noncoding RNA and potential regulatory elements; equivalent changes were not found in male control individuals. Thus, our systematic screen of PTCHD1 and its 5' flanking regions suggests that this locus is involved in ~1% of individuals with ASD and intellectual disability.

De Novo Mutations in FOXP1 in Cases with Intellectual Disability, Autism, and Language Impairment

American Journal of Human Genetics. Nov, 2010  |  Pubmed ID: 20950788

Heterozygous mutations in FOXP2, which encodes a forkhead transcription factor, have been shown to cause developmental verbal dyspraxia and language impairment. FOXP2 and its closest homolog, FOXP1, are coexpressed in brain regions that are important for language and cooperatively regulate developmental processes, raising the possibility that FOXP1 may also be involved in developmental conditions that are associated with language impairment. In order to explore this possibility, we searched for mutations in FOXP1 in patients with intellectual disability (ID; mental retardation) and/or autism spectrum disorders (ASD). We first performed array-based genomic hybridization on sporadic nonsyndromic ID (NSID) (n = 30) or ASD (n = 80) cases. We identified a de novo intragenic deletion encompassing exons 4-14 of FOXP1 in a patient with NSID and autistic features. In addition, sequencing of all coding exons of FOXP1 in sporadic NSID (n = 110) or ASD (n = 135) cases, as well as in 570 controls, revealed the presence of a de novo nonsense mutation (c.1573C>T [p.R525X]) in the conserved forkhead DNA-binding domain in a patient with NSID and autism. Luciferase reporter assays showed that the p.R525X alteration disrupts the activity of the protein. Formal assessments revealed that both patients with de novo mutations in FOXP1 also show severe language impairment, mood lability with physical aggressiveness, and specific obsessions and compulsions. In conclusion, both FOXP1 and FOXP2 are associated with language impairment, but decrease of the former has a more global impact on brain development than that of the latter.

De Novo SYNGAP1 Mutations in Nonsyndromic Intellectual Disability and Autism

Biological Psychiatry. May, 2011  |  Pubmed ID: 21237447

Little is known about the genetics of nonsyndromic intellectual disability (NSID). Recently, we reported de novo truncating mutations in the SYNGAP1 gene of 3 of 94 NSID cases, suggesting that its disruption represents a common cause of autosomal dominant NSID.

Intellectual Disability Without Epilepsy Associated with STXBP1 Disruption

European Journal of Human Genetics : EJHG. May, 2011  |  Pubmed ID: 21364700

STXBP1 (Munc18-1) is a component of the machinery involved in the fusion of secretory vesicles to the presynaptic membrane for the release of neurotransmitters. De novo missense mutations in STXBP1 were recently reported in patients with Ohtahara syndrome, a form of encephalopathy with severe early-onset epilepsy. In addition, sequencing of the coding region of STXBP1 in 95 patients with non-syndromic intellectual disability (NSID) revealed de novo truncating mutations in two patients who also showed severe non-specific epilepsy, suggesting that STXBP1 disruption has the potential of causing a wide spectrum of epileptic disorders in association with intellectual disability. Here, we report on the mutational screening of STXBP1 in a different series of 50 patients with NSID and the identification of a novel de novo truncating mutation (c.1206delT/ p.Y402X) in a male with NSID, but surprisingly with no history of epilepsy. This is the first report of a patient with a truncating mutation in STXBP1 that does not show epilepsy, thus, expanding the clinical spectrum associated with STXBP1 disruption.

Excess of De Novo Deleterious Mutations in Genes Associated with Glutamatergic Systems in Nonsyndromic Intellectual Disability

American Journal of Human Genetics. Mar, 2011  |  Pubmed ID: 21376300

Little is known about the genetics of nonsyndromic intellectual disability (NSID). We hypothesized that de novo mutations (DNMs) in synaptic genes explain an important fraction of sporadic NSID cases. In order to investigate this possibility, we sequenced 197 genes encoding glutamate receptors and a large subset of their known interacting proteins in 95 sporadic cases of NSID. We found 11 DNMs, including ten potentially deleterious mutations (three nonsense, two splicing, one frameshift, four missense) and one neutral mutation (silent) in eight different genes. Calculation of point-substitution DNM rates per functional and neutral site showed significant excess of functional DNMs compared to neutral ones. De novo truncating and/or splicing mutations in SYNGAP1, STXBP1, and SHANK3 were found in six patients and are likely to be pathogenic. De novo missense mutations were found in KIF1A, GRIN1, CACNG2, and EPB41L1. Functional studies showed that all these missense mutations affect protein function in cell culture systems, suggesting that they may be pathogenic. Sequencing these four genes in 50 additional sporadic cases of NSID identified a second DNM in GRIN1 (c.1679_1681dup/p.Ser560dup). This mutation also affects protein function, consistent with structural predictions. None of these mutations or any other DNMs were identified in these genes in 285 healthy controls. This study highlights the importance of the glutamate receptor complexes in NSID and further supports the role of DNMs in this disorder.

A Population Genetic Approach to Mapping Neurological Disorder Genes Using Deep Resequencing

PLoS Genetics. Feb, 2011  |  Pubmed ID: 21383861

Deep resequencing of functional regions in human genomes is key to identifying potentially causal rare variants for complex disorders. Here, we present the results from a large-sample resequencing (n  =  285 patients) study of candidate genes coupled with population genetics and statistical methods to identify rare variants associated with Autism Spectrum Disorder and Schizophrenia. Three genes, MAP1A, GRIN2B, and CACNA1F, were consistently identified by different methods as having significant excess of rare missense mutations in either one or both disease cohorts. In a broader context, we also found that the overall site frequency spectrum of variation in these cases is best explained by population models of both selection and complex demography rather than neutral models or models accounting for complex demography alone. Mutations in the three disease-associated genes explained much of the difference in the overall site frequency spectrum among the cases versus controls. This study demonstrates that genes associated with complex disorders can be mapped using resequencing and analytical methods with sample sizes far smaller than those required by genome-wide association studies. Additionally, our findings support the hypothesis that rare mutations account for a proportion of the phenotypic variance of these complex disorders.

Truncating Mutations in NRXN2 and NRXN1 in Autism Spectrum Disorders and Schizophrenia

Human Genetics. Oct, 2011  |  Pubmed ID: 21424692

Growing genetic evidence is converging in favor of common pathogenic mechanisms for autism spectrum disorders (ASD), intellectual disability (ID or mental retardation) and schizophrenia (SCZ), three neurodevelopmental disorders affecting cognition and behavior. Copy number variations and deleterious mutations in synaptic organizing proteins including NRXN1 have been associated with these neurodevelopmental disorders, but no such associations have been reported for NRXN2 or NRXN3. From resequencing the three neurexin genes in individuals affected by ASD (n = 142), SCZ (n = 143) or non-syndromic ID (n = 94), we identified a truncating mutation in NRXN2 in a patient with ASD inherited from a father with severe language delay and family history of SCZ. We also identified a de novo truncating mutation in NRXN1 in a patient with SCZ, and other potential pathogenic ASD mutations. These truncating mutations result in proteins that fail to promote synaptic differentiation in neuron coculture and fail to bind either of the established postsynaptic binding partners LRRTM2 or NLGN2 in cell binding assays. Our findings link NRXN2 disruption to the pathogenesis of ASD for the first time and further strengthen the involvement of NRXN1 in SCZ, supporting the notion of a common genetic mechanism in these disorders.

SYN1 Loss-of-function Mutations in Autism and Partial Epilepsy Cause Impaired Synaptic Function

Human Molecular Genetics. Jun, 2011  |  Pubmed ID: 21441247

Several genes predisposing to autism spectrum disorders (ASDs) with or without epilepsy have been identified, many of which are implicated in synaptic function. Here we report a Q555X mutation in synapsin 1 (SYN1), an X-linked gene encoding for a neuron-specific phosphoprotein implicated in the regulation of neurotransmitter release and synaptogenesis. This nonsense mutation was found in all affected individuals from a large French-Canadian family segregating epilepsy and ASDs. Additional mutations in SYN1 (A51G, A550T and T567A) were found in 1.0 and 3.5% of French-Canadian individuals with autism and epilepsy, respectively. The majority of these SYN1 mutations were clustered in the proline-rich D-domain which is substrate of multiple protein kinases. When expressed in synapsin I (SynI) knockout (KO) neurons, all the D-domain mutants failed in rescuing the impairment in the size and trafficking of synaptic vesicle pools, whereas the wild-type human SynI fully reverted the KO phenotype. Moreover, the nonsense Q555X mutation had a dramatic impact on phosphorylation by MAPK/Erk and neurite outgrowth, whereas the missense A550T and T567A mutants displayed impaired targeting to nerve terminals. These results demonstrate that SYN1 is a novel predisposing gene to ASDs, in addition to epilepsy, and strengthen the hypothesis that a disturbance of synaptic homeostasis underlies the pathogenesis of both diseases.

Increased Exonic De Novo Mutation Rate in Individuals with Schizophrenia

Nature Genetics. Sep, 2011  |  Pubmed ID: 21743468

Schizophrenia is a severe psychiatric disorder that profoundly affects cognitive, behavioral and emotional processes. The wide spectrum of symptoms and clinical variability in schizophrenia suggest a complex genetic etiology, which is consistent with the numerous loci thus far identified by linkage, copy number variation and association studies. Although schizophrenia heritability may be as high as ∼80%, the genes responsible for much of this heritability remain to be identified. Here we sequenced the exomes of 14 schizophrenia probands and their parents. We identified 15 de novo mutations (DNMs) in eight probands, which is significantly more than expected considering the previously reported DNM rate. In addition, 4 of the 15 identified DNMs are nonsense mutations, which is more than what is expected by chance. Our study supports the notion that DNMs may account for some of the heritability reported for schizophrenia while providing a list of genes possibly involved in disease pathogenesis.

Resequencing of 29 Candidate Genes in Patients with Familial and Sporadic Amyotrophic Lateral Sclerosis

Archives of Neurology. May, 2011  |  Pubmed ID: 21220648

To identify novel disease-causing genes for amyotrophic lateral sclerosis (ALS).

Identification of a Novel In-frame De Novo Mutation in SPTAN1 in Intellectual Disability and Pontocerebellar Atrophy

European Journal of Human Genetics : EJHG. Jan, 2012  |  Pubmed ID: 22258530

Heterozygous in-frame mutations (p.E2207del and p.R2308_M2309dup) in the α-II subunit of spectrin (SPTAN1) were recently identified in two patients with intellectual disability (ID), infantile spasms (IS), hypomyelination, and brain atrophy. These mutations affected the C-terminal domain of the protein, which contains the nucleation site of the α/β spectrin heterodimer. By screening SPTAN1 in 95 patients with idiopathic ID, we found a de novo in-frame mutation (p.Q2202del) in the same C-terminal domain in a patient with mild generalized epilepsy and pontocerebellar atrophy, but without IS, hypomyelination, or other brain structural defects, allowing us to define the core phenotype associated with these C-terminal SPTAN1 mutations. We also found a de novo missense variant (p.R566P) of unclear clinical significance in a patient with non-syndromic ID. These two mutations induced different patterns of aggregation between spectrin subunits in transfected neuronal cell lines, providing a paradigm for the classification of candidate variants.European Journal of Human Genetics advance online publication, 18 January 2012; doi:10.1038/ejhg.2011.271.