Supplementary Material for: Genetic Variations in the Sodium Balance-Regulating Genes <i>ENaC</i>, <i>NEDD4L</i>, <i>NDFIP2</i> and <i>USP2</i> Influence Blood Pressure and Hypertension

Background/Aims: In humans, the kidneys regulate blood pressure by balancing sodium concentrations. Fine-tuning of renal sodium reabsorption and excretion depends on the epithelial sodium channel protein (ENaC: protein complex of SCNN1A, SCNN1B, and SCNN1G). The surface expression of ENaC components is directed by the ubiquitination of ENaC by NEDD4L, an ENaC-specific E3 ubiquitin ligase, and is regulated by the deubiquitination of ENaC by USP2. The activity of NEDD4L in turn is regulated by phosphorylation by SGK1 and also through interaction with NDFIP2. Methods: We analyzed 91 SNPs in 7 genes using the genotype data of 8,842 individuals from the Korea Association REsource subject pool for their correlation with blood pressure and hypertension. Results: 25 SNPs in the SCNN1A, SCNN1B, SCNN1G, NEDD4L, NDFIP2, and USP2 loci were found to be associated with blood pressure. An additional hypertension case-control study identified 13 SNPs in SCNN1B, SCNN1G, and NEDD4L that were linked to hypertension. Conclusion: These results support our hypothesis that individual variations in blood pressure are attributed to variants of the genes that regulate renal sodium reabsorption and excretion. Our data also suggest that it would be meaningful to investigate the role of NEDD4L-mediated ubiquitination in the pathogenesis of hypertension.