Liability to alcohol dependence (AD) is heritable, but little is known
about its complex polygenic architecture or its genetic relationship with other
disorders. To discover loci associated with AD and characterize the relationship
between AD and other psychiatric and behavioral outcomes, we carried out the
largest GWAS to date of DSM-IV diagnosed AD. Genome-wide data on 14,904
individuals with AD and 37,944 controls from 28 case/control and family-based
studies were meta-analyzed, stratified by genetic ancestry (European, N =
46,568; African; N = 6,280). Independent, genome-wide significant effects of
different ADH1B variants were identified in European
(rs1229984; p = 9.8E-13) and African ancestries (rs2066702; p = 2.2E-9).
Significant genetic correlations were observed with 17 phenotypes, including
schizophrenia, ADHD, depression, and use of cigarettes and cannabis. The genetic
underpinnings of AD only partially overlap with those for alcohol consumption,
underscoring the genetic distinction between pathological and non-pathological
drinking behaviors.
Left-right asymmetrical brain function underlies much of human cognition, behavior and emotion. Abnormalities of cerebral asymmetry are associated with schizophrenia and other neuropsychiatric disorders. The molecular, developmental and evolutionary origins of human brain asymmetry are unknown. We found significant association of a haplotype upstream of the gene LRRTM1 (Leucine-rich repeat transmembrane neuronal 1) with a quantitative measure of human handedness in a set of dyslexic siblings, when the haplotype was inherited paternally (P = 0.00002). While we were unable to find this effect in an epidemiological set of twin-based sibships, we did find that the same haplotype is overtransmitted paternally to individuals with schizophrenia/schizoaffective disorder in a study of 1002 affected families (P = 0.0014). We then found direct confirmatory evidence that LRRTM1 is an imprinted gene in humans that shows a variable pattern of maternal downregulation. We also showed that LRRTM1 is expressed during the development of specific forebrain structures, and thus could influence neuronal differentiation and connectivity. This is the first potential genetic influence on human handedness to be identified, and the first putative genetic effect on variability in human brain asymmetry. LRRTM1 is a candidate gene for involvement in several common neurodevelopmental disorders, and may have played a role in human cognitive and behavioral evolution.
Uterine leiomyomata (UL) are the most common neoplasms of the female reproductive tract and primary cause for hysterectomy, leading to considerable morbidity and high economic burden. Here we conduct a GWAS meta-analysis in 35,474 cases and 267,505 female controls of European ancestry, identifying eight novel genome-wide significant (P < 5 × 10−8) loci, in addition to confirming 21 previously reported loci, including multiple independent signals at 10 loci. Phenotypic stratification of UL by heavy menstrual bleeding in 3409 cases and 199,171 female controls reveals genome-wide significant associations at three of the 29 UL loci: 5p15.33 (TERT), 5q35.2 (FGFR4) and 11q22.3 (ATM). Four loci identified in the meta-analysis are also associated with endometriosis risk; an epidemiological meta-analysis across 402,868 women suggests at least a doubling of risk for UL diagnosis among those with a history of endometriosis. These findings increase our understanding of genetic contribution and biology underlying UL development, and suggest overlapping genetic origins with endometriosis.
Background
Given moderately strong genetic contributions to variation in alcoholism and heaviness of drinking (50–60% heritability), with high correlation of genetic influences, we have conducted a quantitative trait genomewide association study for phenotypes related to alcohol use and dependence.
Methods
Diagnostic interview and blood/buccal samples were obtained from sibships ascertained through the Australian Twin Registry. Genomewide SNP genotyping was performed with 8754 individuals [2062 alcohol dependent cases] selected for informativeness for alcohol use disorder and associated quantitative traits. Family-based association tests were performed for alcohol dependence, dependence factor score and heaviness of drinking factor score, with confirmatory case-population control comparisons using an unassessed population control series of 3393 Australians with genomewide SNP data.
Results
No findings reached genomewide significance (p=8.4×10−8 for this study), with lowest p-value for primary phenotypes of 1.2×10−7. Convergent findings for quantitative consumption and diagnostic and quantitative dependence measures suggest possible roles for a transmembrane protein gene (TMEM108) and for ANKS1A. The major finding, however, was small effect sizes estimated for individual SNPs, suggesting that hundreds of genetic variants make modest contributions (1/4% of variance or less) to alcohol dependence risk.
Conclusions
We conclude that (i) meta-analyses of consumption data may contribute usefully to gene-discovery; (ii) translation of human alcoholism GWAS results to drug discovery or clinically useful prediction of risk will be challenging; (iii) through accumulation across studies, GWAS data may become valuable for improved genetic risk differentiation in research in biological psychiatry (e.g. prospective high-risk or resilience studies).
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