Abstract 16819: Sequencing of Genetic Loci Associated With Leukocyte Telomere Length Reveals New Intronic Variants in African Americans

Abstract

Background: Shorter telomere length is associated with an increased risk of coronary artery disease (CAD). A prior genomewide association study (GWAS) on 37,684 European ancestry individuals identified seven loci determining leukocyte telomere length (LTL). A genetic risk score across all 7 loci showed an association with CAD. In this study we sequenced these loci to determine whether the same risk variants could be replicated in African admixed individuals. Methods: We used whole genome sequence data (WGS) in 127 healthy African American subjects from GeneSTAR, a family study of early-onset CAD. LTL was calculated from WGS raw bam data (>30x coverage on the Illumina HiSeq platform) for 7 contiguous repeats of the telomere motif (TTAGGG or CCCTAA, Ding et al., 2014). Tests for association for LTL adjusting for age and sex were performed for a total of 55,821 called variants from ~1Mb subset regions of WGS genotype data centered on each of the 7 European peak GWAS SNPs. Results: We identified a total of 17 variants with p<5x10 -4 mapping to 6 of the 7 regions examined; none of the prior European GWAS peak SNPs were significant. The peak SNP per region in the African Americans included intronic variants rs77138331 in ACYP2 (p=0.0005, MAF = 7%), rs149577640 in NAF1 (p=0.002, MAF=1%), rs35387865 in TERT (p=0.003, MAF = 1%) and rs186486116 in OBFC1 (p=0.004, MAF=1%). Additionally, novel intronic variants not previously observed in dbSNP located at chr19: 22190184 (p=0.005, MAF=1%) and chr2:62445438 (0.005, MAF=2%), mapping to ZNF208 and RTEL1 , were also identified as determinants of LTL. Discussion: This is the first study of telomere length in African Americans using a sequencing approach. We are unable to confirm the European-based GWAS variants but identify several associations mapping to genes of importance in telomere biology. Our results provide evidence that the set of SNPs to be included in calculation of a telomeric genetic CAD risk score may be different in populations of European and African ancestry.