Abstract 1890: Identification of Carboxyl Terminal ADRA1A Variants as Cardiomyopathy Risk Factors by Microarray SNP Analysis Followed by Targeted Deep Resequencing of Cardiomyopathy Cohorts
Familial clustering of sporadic heart failure (HF) suggests an unknown genetic component. We used the ITMAT/Broad/CARe SNP microarray to screen 2000 cardiovascular genes for HF-associated variants in a case-control analysis of two independent Caucasian HF populations (n=755 and 835). Fourteen gene polymorphisms (SNPs) were identified with replicated associations in both study cohorts. Among these was rs12541572, an intronic SNP in the ADRA1A gene encoding α1A adrenergic receptors (P=7.46E-06). Sub-group analysis and further genotyping revealed the ADRA1A SNP association to be specific for non-ischemic HF, and to extend to African American HF as well (n=637). Since this SNP is intronic, we sought to identify causal variants by resequencing coding exons of the ADRA1A gene in the entire case-control study cohort (n>3,700) using the next-generation Illumina GAII sequencing platform. This technique combines DNA into pools averaging ~100 individual DNAs, grouped by race, HF etiology, and diabetes status, for targeted exomic amplification prior to library production and sequencing. Sequence coverage depth averaged ~30×, and pooled sequencing results were confirmed by Sanger sequencing of individual DNAs from one of the study cohorts (n=2,741). Our analysis identified 16 ADRA1A SNPs, 11 that are in dbSNP and 5 that are novel. Allele frequencies were reproducible in different sequencing runs (r=0.981), and for those previously reported were highly correlated with HapMap data. Six SNPs (2 novel) encoded amino acid changes, of which one (rs1048101, R347C) had significantly different allele frequencies between HF cases and controls in African Americans (P=3.0E-06). This SNP encodes an amino acid change in the intracellular carboxyl terminus, which is important for receptor signaling and internalization. Our findings reveal a previously undescribed role in modifying HF risk for an ADRA1A variant that changes amino acid sequence within a critical structural domain of α1A adrenergic receptors.