Genetic Variants in the Natriuretic Peptide Pathway Predict Protein Expression

Abstract

Background: Natriuretic peptides (NP) such as BNP represent a critical physiologic pathway in heart failure, and have important therapeutic and diagnostic applications. However, there is wide variability in system functioning, which may be genetic in origin. We previously showed that genetic variation correlates to RNA quantity in key NP pathway genes, but whether genotype is associated with altered protein expression is unknown.Methods: DNA and tissue samples from non-tumor human kidney (n577) were obtained. Kidney was chosen as target tissue because each of the four candidate genes and proteins (natriuretic peptide receptor (NPR1), NPR2, NPR3 and membrane metallo-endopeptidase (MME)) are expressed there. DNA samples were genotyped for 120 single nucleotide polymorphisms (SNP) in these four genes using a custom Illumina Goldengate array. Target protein concentration was determined in tissue lysates using commercially available enzyme-linked immunosorbent assays for each target. We tested the association of individual SNPs with protein expression using ANOVA, and used a principal components (PC) based regression method for overall SNP association (within each gene) with protein quantity. P-values !0.05 were considered of interest. Multiple comparisons were accounted for by controlling the false discovery rate (FDR) at 0.05. Results: NPR2 showed substantial linkage disequilibrium, and 11 SNPs were associated with protein expression (p!0.05, Figure). These remained significant when FDR was controlled at 0.05. One SNP in MME had a crude association with protein expression (rs3773895, p!0.05) but this did not meet FDR significance. There were no associations of NPR1 or NPR3 genotypes with protein expression. The principle components analysis showed similar results, with PC1 of NPR2 being the only significant association with protein expression. Conclusion: These data suggest that genetic variation in NPR2 impacts protein expression in kidney. Further study is needed to assess whether genetic variation in NPR2 influences NP system physiology, or the effect of exogenous NPs.