A Functional 12T-Insertion Polymorphism in the ATP1A1 Promoter Confers Decreased Susceptibility to Hypertension in a Male Sardinian Population

Abstract

Identification of susceptibility genes for essential hypertension in humans has been a challenge due to its multifactorial pathogenesis complicated by gene-gene and gene-environment interactions, developmental programing and sex specific differences. These concurrent features make identification of causal hypertension susceptibility genes with a single approach difficult, thus requiring multiple lines of evidence involving genetic, biochemical and biological experimentation to establish causal functional mutations. Here we report experimental evidence encompassing genetic, biochemical and in vivo modeling that altogether support ATP1A1 as a hypertension susceptibility gene in males in Sardinia, Italy. ATP1A1 encodes the α1Na,K-ATPase isoform, the sole sodium pump in vascular endothelial and renal tubular epithelial cells. DNA-sequencing detected a 12-nucleotide long thymidine (12T) insertion(ins)/deletion(del) polymorphism within a poly-T sequence (38T vs 26T) in the ATP1A1 5’-regulatory region associated with hypertension in a male Sardinian population. The 12T-insertion allele confers decreased susceptibility to hypertension (P = 0.035; OR = 0.50 [0.28–0.93]) accounting for 12.1 mmHg decrease in systolic BP (P = 0.02) and 6.6 mmHg in diastolic BP (P = 0.046). The ATP1A1 promoter containing the 12T-insertion exhibited decreased transcriptional activity in in vitro reporter-assay systems, indicating decreased α1Na,K-ATPase expression with the 12T-insertion, compared with the 12T-deletion ATP1A1 promoter. To test the effects of decreased α1Na,K-ATPase expression on blood pressure, we measured blood pressure by radiotelemetry in three month-old, highly inbred heterozygous knockout ATP1A1+/− male mice with resultant 58% reduction in ATP1A1 protein levels. Male ATP1A1+/− mice showed significantly lower blood pressure (P < 0.03) than age-matched male wild-type littermate controls. Concordantly, lower ATP1A1 expression is expected to lower Na-reabsorption in the kidney thereby decreasing sodium-associated risk for hypertension and sodium-induced endothelial stiffness and dysfunction. Altogether, data support ATP1A1 as a hypertension susceptibility gene in a male Sardinian population, and mandate further investigation of its involvement in hypertension in the general population.

A Single Nucleotide Polymorphism in SH2B3/LNK Promotes Hypertension Development and Renal Damage

“…[42][43][44][45] These approaches are complicated, however, by the presence of multiple genetic differences in the isolated cells and an inability to test effects of polymorphisms on complex physiological processes such as BP regulation. In vivo approaches include generation of mice with genomic excision of large portions of a gene coding sequence as in classical knockout mice, [46][47][48][49][50][51] however, such studies likely do not recapitulate effects of SNP. Indeed, as observed previously for studies on Sh2b3 in mice and rats, 16,52 genomic deletions of different portions of the coding sequence can yield contrasting results.…”

Connexin 50 Mutation Lowers Blood Pressure in Spontaneously Hypertensive Rat

“…While it is unlikely that a second mutation (distinct from that in Gja8 gene) occurred in SHR-Dca and is responsible for the observed hemodynamic and metabolic effects, it cannot be ruled out absolutely. Potential genes of interest related to cardiovascular pathophysiology within the original interval that lead to identification of the causative Gja8 mutation include ATPase, Na+/K+ transporting, alpha 1 polypeptide (Herrera et al 2015, Orlov et al 2001, gap junction protein alpha 5 (Schmidt et al 2015), or thioredoxin-interacting protein (Yoshioka et al 2012).…”