Abstract Body: Most single nucleotide polymorphisms (SNPs) associated with human blood pressure (BP) are in noncoding regions of the genome and have small effect sizes in the general population. Functional studies in a controlled model system are essential to ascertain the effect of these noncoding loci on blood pressure. Such direct testing is challenging and largely absent, contributing to a critical gap between genetic discoveries and physiological understanding. We reasoned that physiological studies in genetically engineered and phenotypically permissive animal models would help to address this critical gap. We tested the hypothesis by studying the noncoding SNP rs1882961. The T allele of rs1882961, which has a frequency of approximately 30% in the European population, is associated with 0.23 mmHg higher systolic blood pressure in humans. We mapped the human rs1882961 SNP to the rat genome and used CRISPR/Cas9 to delete a 4-bp segment encompassed the rs1882961 orthologous site in the genome of the Dahl salt-sensitive (SS) rat (SS-Δrs1882961). Male SS-Δrs1882961^-/-rats exhibited significantly higher mean arterial pressure (MAP) and systolic and diastolic blood pressures (SBP and DBP) than wild-type littermates after the rats were fed a high-salt (4% NaCl) diet for 14 days (156.6 ± 5.9 vs 149.3 ± 5.1 mmHg for MAP, 179.4 ± 7.8 vs 171.9 ± 6.0 mmHg for SBP, and 133.2 ± 4.6 vs 125.1 ± 4.5 mmHg for DBP; n=7 for SS-Δrs1882961^-/- and 9 for wild-type, p<0.05). In contrast, MAP, SBP, DBP, and pulse pressure of female SS-Δrs1882961^-/-rats were significantly lower than wild-type littermates on a high-salt diet (139.8 ± 1.8 vs 149.5 ± 4.7 mmHg for MAP, 159.3 ± 2.5 vs 172.3 ± 6.0 mmHg for SBP, 116.8 ± 1.5 vs 124.5 ± 3.7 mmHg for DBP, and 42.5 ± 1.6 vs 47.7 ± 2.3 mmHg for pulse pressure; n=8 for SS-Δrs1882961^-/- and 7 for wild-type, p<0.05). The difference in systolic blood pressure reached more than 10 mmHg in female rats. Urinary albumin and protein levels of SS-Δrs1882961^-/- rats after 14 days on a high-salt diet tended to be higher in male and lower in female compared with wild-type littermates.
The remarkable effects on BP as well as the sex-divergent changes resulted from a 4-bp noncoding segment deletion around rs1882961 orthologous site indicate that noncoding genomic segment may have profound impact on phenotypes on permissive genomic background and with informative stressors.