Genetic Dissection of a Blood Pressure Quantitative Trait Locus on Rat Chromosome 1 and Gene Expression Analysis Identifies SPON1 as a Novel Candidate Hypertension Gene

摘要

A region with a major effect on blood pressure is located on rat chromosome 1. We have previously isolated this region in reciprocal congenic strains (WKY.SHR-Sa and SHR.WKY-Sa) derived from a cross of the spontaneously hypertensive rat (SHR) with the Wistar-Kyoto rat (WKY) and shown that there are two distinct BP quantitative trait loci (QTLs), BP1 and BP2, in this region. Sisa1, a congenic sub-strain from the SHR.WKY-Sa animals carrying an introgressed segment of 4.3Mb, contains BP1. Here, we report further dissection of BP1 by the creation of two new mutually exclusive congenic sub-strains (Sisa1a and Sisa1b) and interrogation of candidate genes by expression profiling and targeted transcript sequencing. Only one of the sub-strains (Sisa1a) continued to demonstrate a BP difference but with a reduced introgressed segment of 3Mb. Exonic sequencing of the twenty genes located in the Sisa1a region did not identify any major differences between SHR and WKY. However, microarray expression profiling of whole kidney samples and subsequent quantitative RT-PCR identified a single gene, Spon1 that exhibited significant differential expression between the WKY and SHR genotypes at both 6 and 24 weeks of age. Western blot analysis confirmed an increased level of the Spon1 gene product in SHR kidneys. Spon1 belongs to a family of genes with anti-angiogenic properties. These findings justify further investigation of this novel positional candidate gene in BP control in hypertensive rat models and humans.