RNA-Seq analysis of hearts from NBCe1 Na-HCO3 cotransporter cardiac conditional knockout (K) vs wild-type (W) mice

The purpose of this study was to investigate the hypothesis that cardiomyocyte-specific loss of the electrogenic NBCe1 Na+-HCO3- cotransporter is cardioprotective during in vivo ischemia-reperfusion (IR) injury. An NBCe1 (Slc4a4 gene) cardiac conditional knockout mouse (KO) model was prepared by gene targeting. Cardiovascular performance of wild-type (WT) and cardiac-specific NBCe1 KO mice was analyzed by intraventricular pressure measurements, and changes in cardiac gene expression were determined by RNA Seq analysis. Response to in vivo I/R injury was analyzed after 30 minutes occlusion of the left anterior descending artery followed by 3 hours of reperfusion. Loss of NBCe1 in cardiac myocytes did not impair cardiac contractility or relaxation and caused only limited changes in gene expression patterns, such as those for electrical excitability. However, following ischemia and reperfusion, KO heart sections exhibited significantly fewer apoptotic nuclei than WT sections. These studies indicate that cardiac-specific loss of NBCe1 does not impair cardiovascular performance, causes only minimal changes in gene expression patterns, and protects against I/R injury in vivo. An NBCe1 (Slc4a4 gene) conditional knockout mouse model was prepared. For cardiac myocyte-specific deletion of Slc4a4 exon 12, the mice were bred with a C57Bl6 mouse carrying the Cre recombinase gene driven by the β-myosin promoter, which is active in cardiac myocytes. Total RNA was isolated from whole hearts of 4-month-old male Slc4a4flx/flx and Slc4a4flx/flx(Cre) mice (n = 6 of each genotype). RNA Seq analysis was performed using the Illumina HiSeq 1000 platform, and sequence reads were aligned to the reference mouse genome using TopHat aligner. Statistical analysis was performed using the negative-binomial model of read counts. mRNA expression data are presented as Reads Per Kilobase per Million mapped reads.