Altered structure, regulation, and function of the gene encoding the atrial natriuretic peptide in the stroke-prone spontaneously hypertensive rat

Through the genotype/phenotype cosegregation analysis of an F-2 intercross, from the crossbreeding of stroke-prone spontaneously hypertensive rats (SH RSP) and stroke-resistant spontaneously hypertensive rats (SHR), we previou sly identified a quantitative trait locus for stroke on rat chromosome 5 (S TR2) that colocalized with the genes encoding atrial and brain natriuretic peptides (ANP and BNP) and conferred a stroke-delaying effect. To further c haracterize ANP and BNP as candidates for stroke, we performed additional s tudies, Comparative sequence analysis revealed point mutations in both the coding and regulatory regions of ANP, whereas no interstrain differences we re found for BNP. In in vitro studies in COS-7 and AtT-20 cells that were p erformed to test the relevance of a G-->A substitution at position 1125, a Gly-->Ser transposition in the SHRSP pro-ANP peptide resulted in different posttranslational processing of the SHRSP ANP gene product that was also as sociated with higher cGMP production (P<0.05). Furthermore, an analysis of a 5' end mutation affecting a PEA2 regulatory binding site in the 5' untran slated regulatory sequence of SHRSP ANP demonstrated a significantly lower ANP promoter activation in endothelial cells (P<0.05 versus the SKR ANP). I n addition, the expression of ANP was significantly reduced in the brain, b ut not in the atria, of SHRSP compared with SHR (P<0.0001). No differences were detected with regard to BNP expression. The present results reveal sub stantial differences in ANP, but not BNP, structure and product among SHR a nd SHRSP, which supports a role of ANP in the pathogenesis of stroke in the SHRSP animal model.