Abstract P2013: Transcription Fidelity Dysregulation In Heart Failure Pathogenesis

Abstract

Using deep sequencing combined with computational biology, we found that the failing human hearts (n=3) contain a significant amount of aberrant transcripts arising from widespread spurious intragenic transcription initiations. The same phenomenon was detected in failing mouse hearts (n=3) induced by pressure overload and ischemia injury. Therefore, we hypothesize that spurious transcripts accumulation is a causative factor promoting heart failure (HF). The SET domain containing 2 (Setd2), an H3K36 tri-methylase, is a key regulator for transcription fidelity. The Setd2 modified H3K36me3 prevents RNA polymerase II (Pol II) entry from the gene body and the subsequent cryptic transcription initiation. In the same cohort of failing human and mouse hearts, we found that the SETD2 and H3K36me3 levels were concurrently reduced. To further test our hypothesis, we generated cardiac-specific Setd2-Knockout mice. The mice (n≥8) developed a typical HF progression phenotype: initial compensatory hypertrophy followed by a gradually deteriorating HF with chamber dilation. Transcriptome analysis revealed an accumulation of spurious transcripts in pre-hypertrophic Setd2 -/- cardiomyocytes (n=3). New intragenic transcription initiation sites were identified by DECAP-seq in the knockout (n=3), confirming that the increased aberrant transcripts resulted from spurious Pol II entry. Using ribosome footprinting assay (n=3) to map the translation initiation sites, we found that the aberrant transcripts were partially translated into micro peptides in the Setd2 -/- heart, suggesting that the accumulated aberrant transcripts and micro peptides together promote cardiac hypertrophy. Finally, we developed transgenic mice overexpressing human SETD2 (Tg-MHC-SETD2) in the heart. SETD2 overexpression repressed TAC-induced accumulation of spurious transcripts in cardiomyocytes (n=3). The transgenic mice (n≥6) were resistant to pressure overload stress with less cardiac hypertrophy and improved cardiac contractility. Together, we report that dysregulated transcription fidelity causes adverse aberrant transcripts accumulation leading to cardiac hypertrophy and heart failure. This new mechanism provides potential new therapeutic targets for HF.