Transcriptome-wide association study of attention deficit hyperactivity disorder identifies associated genes and phenotypes
NATURE COMMUNICATIONS
Authors: Liao, Calwing; Laporte, Alexandre D.; Spiegelman, Dan; Akcimen, Fulya; Joober, Ridha; Dion, Patrick A.; Rouleau, Guy A.
Abstract
Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental psychiatric disorder. Genome-wide association studies (GWAS) have identified several loci associated with ADHD. However, understanding the biological relevance of these genetic loci has proven to be difficult. Here, we conduct an ADHD transcriptome-wide association study (TWAS) consisting of 19,099 cases and 34,194 controls and identify 9 transcriptome-wide significant hits, of which 6 genes were not implicated in the original GWAS. We demonstrate that two of the previous GWAS hits can be largely explained by expression regulation. Probabilistic causal fine-mapping of TWAS signals prioritizes KAT2B with a posterior probability of 0.467 in the dorsolateral prefrontal cortex and TMEM161B with a posterior probability of 0.838 in the amygdala. Furthermore, pathway enrichment identifies dopaminergic and norepinephrine pathways, which are highly relevant for ADHD. Overall, our findings highlight the power of TWAS to identify and prioritize putatively causal genes.
KAT2B polymorphism identified for drug abuse in African Americans with regulatory links to drug abuse pathways in human prefrontal cortex
ADDICTION BIOLOGY
Authors: Johnson, Eric O.; Hancock, Dana B.; Levy, Joshua L.; Gaddis, Nathan C.; Page, Grier P.; Glasheen, Cristie; Saccone, Nancy L.; Bierut, Laura J.; Kral, Alex H.
Abstract
Drug abuse is a common and heritable set of disorders, but the underlying genetic factors are largely unknown. We conducted genome-wide association studies of drug abuse using 7 million imputed single nucleotide polymorphisms (SNPs) and insertions/deletions in African Americans (AAs; n=3742) and European Americans (EAs; n=6845). Cases were drawn from the Urban Health Study of street-recruited people, who injected drugs and reported abusing opioids, cocaine, marijuana, stimulants and/or other drugs 10 or more times in the past 30days, and were compared with population controls. Independent replication testing was conducted in 755 AAs and 1131 EAs from the Genetic Association Information Network. An intronic SNP (rs9829896) in the K(lysine) acetyltransferase 2B (KAT2B) gene was significantly associated with drug abuse in AAs (P=4.63x10(-8)) and independently replicated in AAs (P=0.0019). The rs9829896-C allele (frequency=12%) had odds ratios of 0.68 and 0.53 across the AA cohorts: meta-analysis P=3.93x10(-10). Rs9829896-C was not associated with drug abuse across the EA cohorts: frequency=36% and meta-analysis P=0.12. Using dorsolateral prefrontal cortex data from the BrainCloud cohort, we found that rs9829896-C was associated with reduced KAT2B expression in AAs (n=113, P=0.050) but not EAs (n=110, P=0.39). KAT2B encodes a transcriptional regulator in the cyclic adenosine monophosphate and dopamine signaling pathways, and rs9829896-C was associated with expression of genes in these pathways: reduced CREBBP expression (P=0.011) and increased OPRM1 expression (P=0.016), both in AAs only. Our study identified the KAT2B SNP rs9829896 as having novel and biologically plausible associations with drug abuse and gene expression in AAs but not EAs, suggesting ancestry-specific effects.