We determined the electrostatic potential distribution in pristine Pt/Fe:SrTiO3/Nb:SrTiO3 structures by electron holography experiments, revealing the existence of a depletion layer extending into the Nb-doped bottom electrode. Simulations of potential profiles in metal-insulator-metal structures were conducted assuming different types and distributions of dopants. It is found that the presence of acceptor-type dopant concentrations at the Fe:SrTiO3/Nb:SrTiO3 interface with a donor-doped insulating layer provides a good match to the measured profile. Such acceptor-type interface concentrations may be associated with Sr vacancies on the Nb:SrTiO3 side of the bottom interface.
Protein mono-ADP-ribosylation is a reversible post-translational modification of cellular proteins. This scheme of amino-acid modification is used not only by bacterial toxins to attack host cells, but also by endogenous ADP-ribosyltransferases (ARTs) in mammalian cells. These latter ARTs include members of three different families of proteins: the well characterised arginine-specific ecto-enzymes (ARTCs), two sirtuins, and some members of the poly(ADP-ribose) polymerase (PARP/ARTD) family. In the present study, we demonstrate that human ARTC1 is localised to the endoplasmic reticulum (ER), in contrast to the previously characterised ARTC proteins, which are typical GPI-anchored ecto-enzymes. Moreover, using the "macro domain" cognitive binding module to identify ADP-ribosylated proteins, we show here that the ER luminal chaperone GRP78/BiP (glucose-regulated protein of 78 kDa/immunoglobulin heavy-chain-binding protein) is a cellular target of human ARTC1 and hamster ARTC2. We further developed a procedure to visualise ADP-ribosylated proteins using immunofluorescence. With this approach, in cells overexpressing ARTC1, we detected staining of the ER that co-localises with GRP78/BiP, thus confirming that this modification occurs in living cells. In line with the key role of GRP78/BiP in the ER stress response system, we provide evidence here that ARTC1 is activated during the ER stress response, which results in acute ADP-ribosylation of GRP78/BiP paralleling translational inhibition. Thus, this identification of ARTC1 as a regulator of GRP78/BiP defines a novel, previously unsuspected, player in GRP78-mediated ER stress responses.
HMIP-2 is a human quantitative trait locus affecting peripheral numbers, size and hemoglobin composition of red blood cells, with a marked effect on the persistence of the fetal form of hemoglobin, HbF, in adults. The locus consists of multiple common variants in an enhancer region for MYB (chr 6q23.3), which encodes the hematopoietic transcription factor cMYB. Studying a European population cohort and four African-descended groups of patients with sickle cell anemia, we found that all share a set of two spatially separate HbF-promoting alleles at HMIP-2, termed "A" and "B." These typically occurred together ("A-B") on European chromosomes, but existed on separate homologous chromosomes in Africans. Using haplotype signatures for "A" and "B," we interrogated public population datasets. Haplotypes carrying only "A" or "B" were typical for populations in Sub-Saharan Africa. The "A-B" combination was frequent in European, Asian, and Amerindian populations. Both alleles were infrequent in tropical regions, possibly undergoing negative selection by geographical factors, as has been reported for malaria with other hematological traits. We propose that the ascertainment of worldwide distribution patterns for common, HbF-promoting alleles can aid their further genetic characterization, including the investigation of gene-environment interaction during human migration and adaptation.
By using hard X-ray photoelectron spectroscopy experimentally, proof is provided that resistive switching in Ti/Pr?.?? Ca?.?? MnO? (PCMO) devices is based on a redox-process that mainly occurs on the Ti-side. The different resistance states are determined by the amount of fully oxidized Ti-ions in the stack, implying a reversible redox-reaction at the interface, which governs the formation and shortening of an insulating tunnel barrier.
Genetic studies have identified common variants within the intergenic region (HBS1L-MYB) between GTP-binding elongation factor HBS1L and myeloblastosis oncogene MYB on chromosome 6q that are associated with elevated fetal hemoglobin (HbF) levels and alterations of other clinically important human erythroid traits. It is unclear how these noncoding sequence variants affect multiple erythrocyte characteristics. Here, we determined that several HBS1L-MYB intergenic variants affect regulatory elements that are occupied by key erythroid transcription factors within this region. These elements interact with MYB, a critical regulator of erythroid development and HbF levels. We found that several HBS1L-MYB intergenic variants reduce transcription factor binding, affecting long-range interactions with MYB and MYB expression levels. These data provide a functional explanation for the genetic association of HBS1L-MYB intergenic polymorphisms with human erythroid traits and HbF levels. Our results further designate MYB as a target for therapeutic induction of HbF to ameliorate sickle cell and ?-thalassemia disease severity.
Fetal hemoglobin (HbF) is an important modulator of sickle cell disease (SCD). HbF has previously been shown to be affected by variants at three loci on chromosomes 2, 6 and 11, but it is likely that additional loci remain to be discovered.
We report on an analytical model which describes the bipolar resistive switching in electrochemical metallization cells. To simulate the resistive switching, we modeled the growth and dissolution of a metallic filament together with electron tunneling between the growing filament and the counter electrode. The model accounts for the controllability of the low resistive state and the RESET current by tuning the SET current. By analytical analysis the relevant conditions for these generic characteristics are identified. In addition, an explanation for the asymmetry in the SET and RESET switching characteristics is presented. The results of the analytical analysis is generalized to all types of ReRAMs.
The strongly nonlinear switching kinetics of electrochemical metallization memory (ECM) cells are investigated using an advanced 1D simulation model. It is based on the electrochemical growth and dissolution of a Ag or Cu filament within a solid thin film and accounts for nucleation effects, charge transfer, and cation drift. The model predictions are consistent with experimental switching results of a time range of 12 orders of magnitude obtained from silver iodide (AgI) based ECM cells. By analyzing the simulation results the electrochemical processes limiting the switching kinetics are revealed. This study provides new insights into the understanding of the limiting electrochemical processes determining the switching kinetics of ECM cells.
In 1901, the first Nobel Prize in Physiology or Medicine was awarded to Emil von Behring for his ground-breaking discovery of serum therapy: serum from horses vaccinated with toxin-containing culture medium of Corynebacterium diphtheriae contained life-saving antitoxins. The molecular nature of the ADP-ribosylating toxin and the neutralizing antibodies were unraveled only 50 years later. Today, von Behrings antibody therapy is being refined with a new generation of recombinant antibodies and antibody fragments. Nanobodies, which are single-domain antibodies derived from the peculiar heavy-chain antibodies of llamas and other camelids, are emerging as a promising new class of highly specific enzyme inhibitors. In this review, we illustrate the potential of nanobodies as tools to block extracellular and intracellular ADP-ribosyltransferases (ARTs), using the toxin-related membrane-bound mammalian ecto-enzyme ARTC2 and the actin-ADP-ribosylating Salmonella virulence plasmid factor B toxin of Salmonella enterica as examples.
Patients with inherited bone marrow failure syndromes (IBMFS) have stress erythropoiesis, with anaemia, macrocytosis, increased fetal haemoglobin (Hb F) and high erythropoietin levels. In haemoglobinopathies, Hb F levels are regulated by 3 quantitative trait loci, HBS1L-MYB, BCL11A and Xmn1-HBG2. In our study of 97 patients with an IBMFS, increased Hb F was associated with young age, male gender, anaemia, high erythropoietin levels, and alternative alleles in Xmn1-HBG2 [adjusted P = 0·04 for the total group, driven by Fanconi anaemia (P = 0·02) and dyskeratosis congenita (P = 0·09)]. Thus Hb F is regulated in IBMFS by Xmn1-HBG2, as it is in the haemoglobinopathies.
White blood cell (WBC) count is a common clinical measure from complete blood count assays, and it varies widely among healthy individuals. Total WBC count and its constituent subtypes have been shown to be moderately heritable, with the heritability estimates varying across cell types. We studied 19,509 subjects from seven cohorts in a discovery analysis, and 11,823 subjects from ten cohorts for replication analyses, to determine genetic factors influencing variability within the normal hematological range for total WBC count and five WBC subtype measures. Cohort specific data was supplied by the CHARGE, HeamGen, and INGI consortia, as well as independent collaborative studies. We identified and replicated ten associations with total WBC count and five WBC subtypes at seven different genomic loci (total WBC count-6p21 in the HLA region, 17q21 near ORMDL3, and CSF3; neutrophil count-17q21; basophil count- 3p21 near RPN1 and C3orf27; lymphocyte count-6p21, 19p13 at EPS15L1; monocyte count-2q31 at ITGA4, 3q21, 8q24 an intergenic region, 9q31 near EDG2), including three previously reported associations and seven novel associations. To investigate functional relationships among variants contributing to variability in the six WBC traits, we utilized gene expression- and pathways-based analyses. We implemented gene-clustering algorithms to evaluate functional connectivity among implicated loci and showed functional relationships across cell types. Gene expression data from whole blood was utilized to show that significant biological consequences can be extracted from our genome-wide analyses, with effect estimates for significant loci from the meta-analyses being highly corellated with the proximal gene expression. In addition, collaborative efforts between the groups contributing to this study and related studies conducted by the COGENT and RIKEN groups allowed for the examination of effect homogeneity for genome-wide significant associations across populations of diverse ancestral backgrounds.
We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to hemoglobinopathies and thalassemia and implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories. A total of 1,941 unique genetic variants in 37 genes, encoding globins and other erythroid proteins, are currently documented in these databases, with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants, leading to a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The principles established here will serve as a model for other systems and for the analysis of other common and/or complex human genetic diseases.
Cytotoxic precipitation of free ?-globin monomers and its production of reactive oxygen species cause red cell membrane damage that leads to anemia and eventually ineffective erythropoiesis in ?-thalassemia. Alpha hemoglobin stabilizing protein (AHSP) was found to bind only to free ?-globin monomers creating a stable and inert complex which remains soluble in the cytoplasm thus preventing harmful precipitations. Alpha hemoglobin stabilizing protein was shown to bind nascent ?-globin monomers with transient strength before transferring ?-globin to ?-globin to form hemoglobin tetramer. A classical twin study would be beneficial to investigate the role of genetics and environment in the variation of alpha hemoglobin stabilizing protein expression as this knowledge will enable us to determine further investigations with regards to therapeutic interventions if alpha hemoglobin stabilizing protein is to be a therapeutic agent for ?-thalassemia. This study investigates the heritability influence of alpha hemoglobin stabilizing protein expression and factors that may contribute to this. Results indicated that a major proportion of alpha hemoglobin stabilizing protein expression was influenced by genetic heritability (46%) with cis-acting factors accounting for 19% and trans-acting factors at 27%.
Fetal hemoglobin (HbF, ?(2)?(2)) is a major contributor to the remarkable phenotypic heterogeneity of sickle cell anemia (SCA). Genetic variation at 3 principal loci (HBB cluster on chromosome 11p, HBS1L-MYB region on chromosome 6q, and BCL11A on chromosome 2p) have been shown to influence HbF levels and disease severity in ?-thalassemia and SCA. Previous studies in SCA, however, have been restricted to populations from the African diaspora, which include multiple genealogies. We have investigated the influence of these 3 loci on HbF levels in sickle cell patients from Tanzania and in a small group of African British sickle patients. All 3 loci have a significant impact on the trait in both patient groups. The results suggest the presence of HBS1L-MYB variants affecting HbF in patients who are not tracked well by European-derived markers, such as rs9399137. Additional loci may be identified through independent genome-wide association studies in African populations.
Sickle cell anemia is caused by a single type of mutation, a homozygous A?T substitution in the ß globin gene. Clinical severity is diverse, partially due to additional, disease-modifying genetic factors. We are studying one such modifier locus, HMIP (HBS1L-MYB intergenic polymorphism, chromosome 6q23.3). Working with a genetically admixed patient population, we have encountered the necessity to generate haplotype signatures of genetic markers to label genomic fragments with distinct genealogical origin at this locus. With the goal to generate haplotype signatures from patients experimentally, we have investigated the suitability of an existing nanofluidic assay platform to perform phase alignment with single-nucleotide polymorphism alleles.
Increased levels of fetal hemoglobin (HbF, alpha(2)gamma(2)) are of no consequence in healthy adults, but confer major clinical benefits in patients with sickle cell anemia (SCA) and beta thalassemia, diseases that represent major public health problems. Inter-individual HbF variation is largely genetically controlled, with one extreme caused by mutations involving the beta globin gene (HBB) complex, historically referred to as pancellular hereditary persistence of fetal hemoglobin (HPFH). These Mendelian forms of HPFH are rare and do not explain the common form of heterocellular HPFH which represents the upper tail of normal HbF variation, and is clearly inherited as a quantitative genetic trait. Genetic studies have identified three major quantitative trait loci (QTLs) (Xmn1-HBG2, HBS1L-MYB intergenic region on chromosome 6q23, and BCL11A on chromosome 2p16) that account for 20-50% of the common variation in HbF levels in patients with SCA and beta thalassemia, and in healthy adults. Two of the major QTLs include oncogenes, emphasizing the importance of cell proliferation and differentiation as an important contribution to the HbF phenotype. The review traces the story of HbF quantitative genetics that uncannily mirrors the changing focus in genetic methodology, from candidate genes through positional cloning, to genome-wide association, that have expedited the dissection of the genetic architecture underlying HbF variability. These genetic results have already provided remarkable insights into molecular mechanisms that underlie the hemoglobin switch.
Sickle cell disease (SCD) and beta thalassaemia, caused by lesions that affect the HBB (beta globin gene), form the most common human genetic disorders world-wide, and represent a major public health problem. Inter-individual variation in foetal haemoglobin (HbF) expression is a known and heritable disease modifier; high HbF levels are correlated with reduced morbidity and mortality in both diseases. This review traces our progress in the understanding of the persistence of HbF in adults as a quantitative trait and the genetic approaches used in teasing out the loci contributing to its variability in normal populations and in patients with haemoglobinopathies. Three major loci -- Xmn1-HBG2 single nucleotide polymorphism, HBS1L-MYB intergenic region on chromosome 6q, and BCL11A -- contribute 20-50% of the trait variance in patients with sickle cell anaemia and healthy European Caucasians. It is likely that the remaining trait variance is due to numerous other loci, many contributing modest effects. Identification of the three major loci has not yet been translated into new therapeutic approaches for HbF reactivation but an immediate application would be an improved prediction of ones ability to produce HbF, which in turn, may improve prediction of disease severity.
The number and volume of cells in the blood affect a wide range of disorders including cancer and cardiovascular, metabolic, infectious and immune conditions. We consider here the genetic variation in eight clinically relevant hematological parameters, including hemoglobin levels, red and white blood cell counts and platelet counts and volume. We describe common variants within 22 genetic loci reproducibly associated with these hematological parameters in 13,943 samples from six European population-based studies, including 6 associated with red blood cell parameters, 15 associated with platelet parameters and 1 associated with total white blood cell count. We further identified a long-range haplotype at 12q24 associated with coronary artery disease and myocardial infarction in 9,479 cases and 10,527 controls. We show that this haplotype demonstrates extensive disease pleiotropy, as it contains known risk loci for type 1 diabetes, hypertension and celiac disease and has been spread by a selective sweep specific to European and geographically nearby populations.
Mean platelet volume (MPV) and platelet count (PLT) are highly heritable and tightly regulated traits. We performed a genome-wide association study for MPV and identified one SNP, rs342293, as having highly significant and reproducible association with MPV (per-G allele effect 0.016 +/- 0.001 log fL; P < 1.08 x 10(-24)) and PLT (per-G effect -4.55 +/- 0.80 10(9)/L; P < 7.19 x 10(-8)) in 8586 healthy subjects. Whole-genome expression analysis in the 1-MB region showed a significant association with platelet transcript levels for PIK3CG (n = 35; P = .047). The G allele at rs342293 was also associated with decreased binding of annexin V to platelets activated with collagen-related peptide (n = 84; P = .003). The region 7q22.3 identifies the first QTL influencing platelet volume, counts, and function in healthy subjects. Notably, the association signal maps to a chromosome region implicated in myeloid malignancies, indicating this site as an important regulatory site for hematopoiesis. The identification of loci regulating MPV by this and other studies will increase our insight in the processes of megakaryopoiesis and proplatelet formation, and it may aid the identification of genes that are somatically mutated in essential thrombocytosis.
Fetal haemoglobin (HbF) is a major ameliorating factor in sickle cell disease. We investigated if a quantitative trait locus on chromosome 6q23 was significantly associated with HbF and F cell levels in individuals of African descent. Single nucleotide polymorphisms (SNPs) in a 24-kb intergenic region, 33-kb upstream of the HBS1L gene and 80-kb upstream of the MYB gene, were typed in 177 healthy Afro-Caribbean subjects (AC) of approximately 7% European admixture, 631 healthy Afro-Germans (AG, a group of African and German descendents located in rural Jamaica with about 20% European admixture), 87 West African and Afro-Caribbean individuals with sickle cell anaemia (HbSS), as well as 75 Northern Europeans, which served as a contrasting population. Association with a tag SNP for the locus was detected in all four groups (AC, P = 0.005, AG, P = 0.002, HbSS patients, P = 0.019, Europeans, P = 1.5 x 10(-7)). The association signal varied across the interval in the African-descended groups, while it is more uniform in Europeans. The 6q QTL for HbF traits is present in populations of African origin and is also acting in sickle cell anaemia patients. We have started to distinguish effects originating from European and African ancestral populations in our admixed study populations.
High levels of fetal haemoglobin (HbF) are protective in beta-haemoglobinopathies. The proportion of erythrocytes containing HbF (F-cells, FC) was measured in healthy adults of African and Caucasian ancestry to assess the feasibility of localizing genes for the FC trait using admixture mapping. Participants were Afro-Caribbean (AC) blood donors and residents of a rural enclave with a history of recent German admixture (Afro-German, AG) recruited in Jamaica, and Caucasian Europeans recruited in Jamaica and the UK. FC levels were significantly different between groups (P < 0.001); the geometric mean FC level in the AC sample (n = 176) was 3.75% [95% confidence interval (CI) 3.36-4.18], AG sample (n = 631) was 2.77% (95% CI 2.63-2.92), and among Caucasians (n = 1099) was 3.26% (95% CI 3.13-3.39). After adjustment for age, sex, haemoglobin electrophoresis pattern, and HBG2 genotype, FC levels in the AC group remained significantly different (P < 0.001) from those in the Caucasian and the AG group but the difference between the Caucasian and AG groups became non-significant (P = 0.46) despite substantial differences in average ancestry. The data confirm ethnic differences in FC levels and indicate the potential usefulness of these populations for admixture mapping of genes for FC levels.
Using a genome-wide association study, we found that common inter-individual differences in haemoglobin A(2) (HbA(2) , ?(2) ?(2) ) levels are largely governed by genetic factors (42% of variability). The influence of age (1%) and sex (4%) was small. HbA(2) levels were influenced by two loci: the HBS1L-MYB locus on chromosome 6q, which has been shown to have pleiotropic effects on other haematological traits; and a second locus surrounding HBB, the gene encoding ?-globin. Our results suggest that HbA(2) levels in adults are influenced by two different biological processes: one via kinetics of erythropoiesis, and the other, via competition between HBB and HBD activity.
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