Mapping genomic loci implicates genes and synaptic biology in schizophrenia

Schizophrenia has a heritability of 60-80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

Mapping genomic loci prioritises genes and implicates synaptic biology in schizophrenia

Schizophrenia has a heritability of 60–80%1, much of which is attributable to common risk alleles. Here, in a two-stage genome-wide association study of up to 76,755 individuals with schizophrenia and 243,649 control individuals, we report common variant associations at 287 distinct genomic loci. Associations were concentrated in genes that are expressed in excitatory and inhibitory neurons of the central nervous system, but not in other tissues or cell types. Using fine-mapping and functional genomic data, we identify 120 genes (106 protein-coding) that are likely to underpin associations at some of these loci, including 16 genes with credible causal non-synonymous or untranslated region variation. We also implicate fundamental processes related to neuronal function, including synaptic organization, differentiation and transmission. Fine-mapped candidates were enriched for genes associated with rare disruptive coding variants in people with schizophrenia, including the glutamate receptor subunit GRIN2A and transcription factor SP4, and were also enriched for genes implicated by such variants in neurodevelopmental disorders. We identify biological processes relevant to schizophrenia pathophysiology; show convergence of common and rare variant associations in schizophrenia and neurodevelopmental disorders; and provide a resource of prioritized genes and variants to advance mechanistic studies

The Influence of the CTIP Polymorphism, Q418P, on Homologous Recombination and Predisposition to Radiation-Induced Tumorigenesis (mainly rAML) in Mice

Exposure to ionizing radiation increases the incidence of acute myeloid leukemia (AML), which has been diagnosed in Japanese atomic bombing survivors, as well as patients treated with radiotherapy. The genetic basis for susceptibility to radiation-induced AML is not well characterized. We previously identified a candidate murine gene for susceptibility to radiation-induced AML (rAML): C-terminal binding protein (CTBP)-interacting protein (CTIP)/retinoblastoma binding protein 8 (RBBP8). This gene is essential for embryonic development, double-strand break (DSB) resection in homologous recombination (HR) and tumor suppression. In the 129S2/SvHsd mouse strain, a nonsynonymous single nucleotide polymorphism (nsSNP) in Ctip, Q418P, has been identified. We investigated the role of Q418P in radiation-induced carcinogenesis and its effect on CTIP function in HR. After whole-body exposure to 3 Gy of X rays, 11 out of 113 (9.7%) 129S2/SvHsd mice developed rAML. Furthermore, 129S2/SvHsd mouse embryonic fibroblasts (MEFs) showed lower levels of recruitment of HR factors, Rad51 and replication protein A (RPA) to radiation-induced foci, compared to CBA/H and C57BL/6 MEFs, isolated from rAML-sensitive and resistant strains, respectively. Mitomycin C and alpha particles induced lower levels of sister chromatid exchanges in 129S2/SvHsd cells compared to CBA/H and C57BL/6. Our data demonstrate that Q418P nsSNP influences the efficiency of CTIP function in HR repair of DNA DSBs in vitro and in vivo, and appears to affect susceptibility to rAML

Macaques Infected with a CCR5-Tropic Simian/Human Immunodeficiency Virus (SHIV) Develop Broadly Reactive Anti-HIV Neutralizing Antibodies▿

The development of anti-human immunodeficiency virus (anti-HIV) neutralizing antibodies and the evolution of the viral envelope glycoprotein were monitored in rhesus macaques infected with a CCR5-tropic simian/human immunodeficiency virus (SHIV), SHIVSF162P4. Homologous neutralizing antibodies developed within the first month of infection in the majority of animals, and their titers were independent of the extent and duration of viral replication during chronic infection. The appearance of homologous neutralizing antibody responses was preceded by the appearance of amino acid changes in specific variable and conserved regions of gp120. Amino acid changes first appeared in the V1, V2, C2, and V3 regions and subsequently in the C3, V4, and V5 regions. Heterologous neutralizing antibody responses developed over time only in animals with sustained plasma viremia. Within 2 years postinfection the breadth of these responses was as broad as that observed in certain patients infected with HIV type 1 (HIV-1) for over a decade. Despite the development of broad anti-HIV-1 neutralizing antibody responses, viral replication persisted in these animals due to viral escape. Our studies indicate that cross-reactive neutralizing antibodies are elicited in a subset of SHIVSF162P4 infected macaques and that their development requires continuous viral replication for extended periods of time. More importantly, their late appearance does not prevent progression to disease. The availability of an animal model where cross-reactive anti-HIV neutralizing antibodies are developed may facilitate the identification of virologic and immunologic factors conducive to the development of such antibodies

Comparative genome and proteome analysis of Anopheles gambiae and Drosophila melanogaster

Comparison of the genomes and proteomes of the two diptera Anopheles gambiae and Drosophila melanogaster, which diverged about 250 million years ago, reveals considerable similarities. However, numerous differences are also observed; some of these must reflect the selection and subsequent adaptation associated with different ecologies and life strategies. Almost half of the genes in both genomes are interpreted as orthologs and show an average sequence identity of about 56%, which is slightly lower than that observed between the orthologs of the pufferfish and human (diverged about 450 million years ago). This indicates that these two insects diverged considerably faster than vertebrates. Aligned sequences reveal that orthologous genes have retained only half of their intron/exon structure, indicating that intron gains or losses have occurred at a rate of about one per gene per 125 million years. Chromosomal arms exhibit significant remnants of homology between the two species, although only 34% of the genes colocalize in small "microsyntenic" clusters, and major interarm transfers as well as intra-arm shuffling of gene order are detected

SLAP/SLAP2 prevent excessive platelet (hem)ITAM signaling in thrombosis and ischemic stroke in mice

Glycoprotein VI and C-type lectin-like receptor 2 are essential platelet activating receptors in hemostasis and thrombo-inflammatory disease, which signal through a (hem)immunoreceptor tyrosine-based activation motif (ITAM)-dependent pathway. The adapter molecules Src-like adapter proteins (SLAP and SLAP2) are involved in the regulation of immune cell surface expression and signaling, but their function in platelets is unknown. In this study, we show that platelets expressed both SLAP isoforms and that overexpression of either protein in a heterologous cell line almost completely inhibited glycoprotein VI and C-type lectin-like receptor 2 signaling. In mice, single deficiency of SLAP or SLAP2 had only moderate effects on platelet function, whereas double deficiency of both adapters resulted in markedly increased signal transduction, integrin activation, granule release, aggregation, procoagulant activity, and thrombin generation in response to (hem)ITAM-coupled, but not G protein-coupled, receptor activation. In vivo, constitutive SLAP/SLAP2 knockout mice displayed accelerated occlusive arterial thrombus formation and a dramatically worsened outcome after focal cerebral ischemia. This was attributed to the absence of both adapter proteins in platelets, as demonstrated by adoptive transfer of Slap(-/-)/Slap2(-/-) platelets into wild-type mice. Our results establish SLAP and SLAP2 as critical inhibitors of platelet (hem)ITAM signaling in the setting of arterial thrombosis and ischemic stroke