Abstract 435: Post-transcriptional Regulation of Tropomyosin Isoforms Altered in Human Heart Diseases

Abstract

Background: Tropomyosin 1 (TPM1) is a coiled coil protein that forms polymers along with the actin filament, and it is required for myofibril organization, myocardial contraction, and cardiac development. TPM1 has cardiac muscle and non-muscle specific protein isoforms that dictate its function in cardiac muscle contraction or in cytoskeleton. TPM1 mutations in exon 2b, 5, 6b or 8 are associated with cardiovascular diseases including familial hypertrophic cardiomyopathy, dilated cardiomyopathy and left ventricular non-compaction. Thus, it is of great importance to investigate the mechanisms that control tropomyosin isoforms in order to identify novel therapeutic targets for cardiovascular diseases in which TPM1 is mutated. Method: We used nanopore sequencing technology using MinION and poly(A)click seq (PAC-seq) to identify different TPM1 transcripts generated in rat heart derived H9c2 cells. RT-PCR and western blotting were conducted to measure mRNA and protein levels of TPM1 respectively. Results: We identified 10 different isoforms of TPM1 using nanopore sequencing and determined several exons that are extensively spliced and favored in cardiac cells. We further identified an RNA binding protein that controls cardiac specific isoforms of TPM1 via alternative splicing and polyadenylation. Importantly, we found that this RNA binding protein regulates alternative splicing of exon 6b of TPM1, which is mutated in patients with cardiomyopathies. Conclusions: We identified an RNA binding protein, which controls expression of cardiac specific TPM1 isoforms by alternative polyadenylation and alternative splicing.