RNA-seq identifies novel transcript elements and transcript processing in the normal and failing hearts

Changes in gene expression contribute to the pathogenesis of heart failure. The sequence, expression level, and structure of the human cardiac transcriptome are incompletely described, as are their changes in heart disease. High throughput transcriptome sequencing (RNA-seq) is a quantitative and unbiased approach to measure transcript level and to identify novel transcribed elements or transcript splicing. Here we acquired 975.2 x 106 mapped RNA-seq reads in 15 control and 15 ischemic cardiomyopathy (ICM) hearts, obtained at the time of heart transplantation. We identified over 1000 differentially expressed transcripts, and thousands of novel transcribed elements, some of which were differentially expressed in between control and ICM groups. We found that transcript processing of several cardiac genes was deranged in ICM. For instance, the ratio between specific MYH6 exons was significantly changed in ICM compared to controls, while this type of inter-exon variation was not observed for the adjoining gene MYH7. This RNA-seq study of the human heart failure transcriptome revealed the diversity of transcripts expressed in the human heart and their complex patterns of expression in the diseased heart. Overall design: Transcriptome profiling (RNA-seq) of 15 control and 15 ischemic cardiomyopathy (ICM) hearts using Illumina GAII and SOLiD