Neither the New Zealand Genetically Hypertensive Strain nor Dahl Salt-Sensitive Strain Has an A1079T Transversion in the α1 Isoform of the Na + ,K + -ATPase Gene

Abstract

A putative 1079A→T mutation in the α1 isoform of the Na + , K + -ATPase ( Atp1a1 ) gene of the Dahl salt-sensitive rat inbred by John Rapp (SS/Jr) strain was projected to cause a conformation change in the membrane hydrophobic region of the protein product, possibly resulting in hypertension. The existence of the mutation was challenged, but the challenge was apparently rebutted. The New Zealand genetically hypertensive (GH) rat is known to have a blood pressure quantitative trait locus on chromosome 2 containing the gene for the ATPase. Thus, we sought to determine whether the GH rat carried the 1079A→T transversion. We chose a method, first nucleotide change analysis, that can detect point mutations in a mixed population of polymerase chain reaction (PCR) products, even in the presence of PCR bias, and confirmed our analysis by restriction enzyme digestion of PCR products. To ensure the validity of our analyses, we used site-directed mutagenesis to create positive controls containing the mutation. Surprisingly, we found that neither the GH nor the SS/Jr strain had the A1079T transversion. Indeed, the transversion was not found in any strain tested. As an incidental observation, we have sequenced the intron preceding the exon containing the putative A1079T transversion. Within this intron, a single-base C/T polymorphism was observed at base 132. Our results definitively eliminate the putative A1079T transversion in Atp1a1 as a causative factor underlying hypertension in the GH, spontaneously hypertensive, and SS/Jr rat strains and indicate that alternative candidate genes in the region defined by the chromosome 2 hypertension quantitative trait locus should be examined.