The Impact of the Blood Pressure- Associated Genetic Locus at SLC4A7 on Gene Expression and Intracellular pH Regulation
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Genome-wide association studies have revealed an association between variation at the SLC4A7 locus and blood pressure. SLC4A7 encodes the electroneutral Na+/HCO3 – co-transporter NBCn1 which regulates intracellular pH (pHi) in a range of tissues, including vascular smooth muscle and endothelium. Notably, the SLC4A7 knockout mouse has been shown to have an altered blood pressure phenotype. This thesis presents a functional study of variants at this locus in primary cultures of vascular smooth muscle and endothelial cells. There were genotype-dependent differences in DNA-nuclear protein interactions by formaldehyde-assisted isolation of regulatory elements, electrophoretic mobility shift assays and DNA pulldown assays. Subsequently, there were also genotypedependent differences in SLC4A7 expression level and NBCn1 availability at the plasma membrane. In turn, SLC4A7 genotype is associated with Na+/HCO3 –-dependent steady-state pHi and recovery from intracellular acidosis. The genotypic effect on pHi regulation was independent of the calcineurin activity, or the amino acid substitution E326K resulting from a missense polymorphism. However, in the presence of Na+/H+ exchange activity, the SLC4A7 genotypic effect on net base uptake and steady-state pHi was detected only in vascular smooth muscle cells but not endothelial cells. The finding of a genotypic influence on SLC4A7 expression and pHi regulation in vascular smooth muscle cells provide an insight into the molecular mechanism underlying the association of variation at the SLC4A7 locus with blood pressure.
AuthorsNg, Fu Liang
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