Cocaine dependence is a complex neuropsychiatric disorder that is highly comorbid with other psychiatric traits. Association studies suggest that common genetic variants contribute substantially to cocaine dependence susceptibility. Also, increasing evidence supports the role of shared genetic risk factors in the lifetime co-occurrence of psychiatric traits and cocaine dependence. Here we performed a genome-wide association study (GWAS) meta-analysis of cocaine dependence using four different dbGaP datasets (2,085 cases and 4,293 controls).Although no genome-wide significant hits were found in the SNP-based analysis, the gene-based analysis identified HIST1H2BD as significantly associated with cocaine-dependence (10% FDR).This gene is located in a region on chromosome 6 enriched in histone-related genes, previously associated with schizophrenia. The top SNPs of this region, rs806973 and rs56401801 (P=3.14e-06 and 3.44e-06, respectively), are eQTLs for different genes in multiple brain areas.Furthermore, we performed LD Score regression (LDSC) analysis with comorbid conditions and found significant genetic correlations between cocaine dependence and ADHD, SCZ, MDD and risk-taking behavior. We also found, through polygenic risk score (PRS)
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder caused by an interplay of genetic and environmental factors. Epigenetics is crucial to lasting changes in gene expression in the brain. Recent studies suggest a role for DNA methylation in ADHD. We explored the contribution to ADHD of allele-specific methylation (ASM), an epigenetic mechanism that involves SNPs correlating with differential levels of DNA methylation at CpG sites. We selected 3896 tagSNPs reported to influence methylation in human brain regions and performed a casecontrol association study using the summary statistics from the largest GWAS meta-analysis of ADHD, comprising 20,183 cases and 35,191 controls. We observed that genetic risk variants for ADHD are enriched in ASM SNPs and identified associations with eight tagSNPs that were significant at a 5% false discovery rate (FDR). These SNPs correlated with methylation of CpG sites lying in the promoter regions of six genes. Since methylation may affect gene expression, we inspected these ASM SNPs together with 52 ASM SNPs in high LD with them for eQTLs in brain tissues and observed that the expression of three of those genes was affected by them. ADHD risk alleles correlated with increased expression (and decreased methylation) of ARTN and PIDD1 and with a decreased expression (and increased methylation) of C2orf82. Furthermore, these three genes were predicted to have altered expression in ADHD, and genetic variants in C2orf82 correlated with brain volumes. In summary, we followed a systematic approach to identify risk variants for ADHD that correlated with differential cis-methylation, identifying three novel genes contributing to the disorder.
For over a century, mice have been used to model human disease, leading to many fundamental discoveries about mammalian biology and the development of new therapies. Mouse genetics research has been further catalysed by a plethora of genomic resources developed in the last 20 years, including the genome sequence of C57BL/6J and more recently the first draft reference genomes for 16 additional laboratory strains. Collectively, the comparison of these genomes highlights the extreme diversity that exists at loci associated with the immune system, pathogen response, and key sensory functions, which form the foundation for dissecting phenotypic traits in vivo. We review the current status of the mouse genome across the diversity of the mouse lineage and discuss the value of mice to understanding human disease.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.