Transcriptional analysis of atrial and ventricular muscles from rats

Previous studies have used microarray technology to explore gene expression differences between the atrium and the ventricle. However, selection criteria for the differentially expressed genes (DEGs) based only on either the fold change or the P value in these studies. Here, we aim to further identify the DEGs by setting a P value threshold of <0.05 and a fold change of >2, which may yield more specific gene expression differences between the atrium and the ventricle. Gene expression profiling of the atrial appendages and the ventricular free walls in 13 normal male Sprague Dawley rats were obtained from the Gene Expression Omnibus data base (accession No.: GSE5266). DEGs between the atrial and the ventricular samples were screened using the microarray significance analysis. The underlying functions of DEGs were predicted by gene ontology and pathway enrichment analyses. In addition, we also constructed protein interactions networks, and analyzed the function modules of the interacting proteins by MCODE. A total of 757DEGs between the atria and the ventricles were found. The genes highly expressed in the ventricular myocytes were associated with muscle contraction (e.g., Myl1, Myl2, Myl3, and Myh7) and energy production (e.g., Acadm and Acsl6), while the genes preferentially expressed in the atrial myocytes were involved in the integration of neurohumoral signals (e.g., Cldn1). These conclusions were confirmed by pathway enrichment and function module analyses. Our present study provides an overview of the transcript level differences between the atrium and the ventricle, which may be useful for determination of potential biomarkers.