Abstract 070: Deletion Of A Non-coding Genomic Segment Orthologous To The Human Rs1173771 Haplotype Region Attenuates Hypertension In Dahl Salt-sensitive Rats

Abstract

Most SNPs associated by GWAS with blood pressure (BP) phenotypes are located in noncoding regions of DNA. Investigating the physiological effects of these SNPs and their underlying mechanisms will advance our understanding of how genetic and epigenetic mechanisms regulate BP. The BP-associated SNP rs1173771 is in linkage disequilibrium (LD) with 10 other SNPs (r 2 >0.80) forming a haplotype spanning 17.5 kb of noncoding DNA. We explored the effects of the rs1173771 LD orthologous region on BP on the genetic background of Dahl salt-sensitive (SS) rats and the physiological and molecular mechanisms involved. A ~29.5 kb noncoding segment on rat chromosome 5 orthologous to the human rs1173771 LD region was identified using LiftOver. The model SS-rs1173771LD -/- was generated using CRISPR-Cas9 to delete this region in SS rats. BP was not significantly different between SS-rs1173771LD -/- rats and wildtype (WT) littermates on a 0.4% NaCl diet. After 14 days of a 4% NaCl diet, 24-hour mean arterial pressure (MAP) and systolic blood pressure (SBP) of SS-rs1173771LD -/- male rats were significantly lower compared with WT (149.1 ± 2.7 vs 155.9 ± 2.5 mmHg for MAP and 169.6 ± 4.3 vs 179.0 ± 3.0 mmHg for SBP). No difference in diastolic blood pressure was observed. No significant difference of BP was observed between genotypes in females. The transcription start sites of human natriuretic peptide receptor 3 (NPR3) and rat Npr3 are located ~129-kbp and ~80-kbp from the human rs1173771 LD region and the rat orthologous region, respectively. RNA-seq indicated that Npr3 expression was upregulated in the mesenteric artery in SS-rs1173771LD -/- rats. Vasodilation of mesenteric arteries in response to C-type natriuretic peptide was significantly enhanced in SS-rs1173771LD -/- male rats compared with WT littermates. A selective NPR-C antagonist abolished vasodilation in both groups, suggesting the vasorelaxation was NPR-C dependent. In conclusion, deletion of the rs1173771 LD orthologous region increased mesenteric artery vasorelaxation and attenuated salt-induced hypertension in male SS rats. Our findings provided evidence that evolutionarily conserved noncoding DNA regions located far from protein-coding genes can influence BP in vivo.