Abstract P2070: Insights Into RBM20 Cardiomyopathy Revealed By Global Proteomics

Abstract

Patients with missense mutations in RNA binding motif protein 20 (RBM20), an RNA binding protein and splicing factor, develop a clinically aggressive form of dilated cardiomyopathy (DCM). Recent studies revealed that DCM-linked RBM20 missense mutations promote re-localization of the protein from the nucleus to the cytoplasm where it forms ribonucleoprotein (RNP) granules—non-membrane bound assemblies formed from RNAs and RNA regulatory proteins. The sequestration of RNAs and RNA regulatory proteins in these granules has the potential to dramatically alter the landscape of protein expression in the cardiomyocyte; yet, how RBM20 missense mutations impact global gene expression at the protein level has not been explored. Herein, we utilized mass spectrometry (MS)-based proteomics to identify global changes in protein expression in cardiac tissue harvested from mutation knock-in (KI) mice harboring the DCM-linked S637A and S639G RBM20 mutations. Our analysis revealed a total of 212 and 190 differentially expressed proteins (DEPs) in S637A and S639G KI mice, respectively, relative to wild-type. In general, identified DEPs were similar between KI mice with 81 and 38 proteins commonly up- and down-regulated, respectively. Consistent with mutant RBM20-mediated granule formation, 15 and 12 of the up-regulated proteins in S637A and S639G KI mice, respectively, have previously been implicated in granule assembly. Other up-regulated proteins in KI mice included chaperones and cytoskeletal proteins, as well as proteins involved in RNA metabolism and metabolite interconversion. Interestingly, proteins involved in the regulation of metabolite interconversion were also the most common protein class down-regulated in both KI mice, suggesting that broad changes in cellular metabolism may be a common feature associated with the RBM20 S637A and S639G missense mutations. Additionally, our proteomics analysis confirmed the differential expression of approximately 20-30% of previously identified differentially expressed genes based on RNAseq analyses from S637A and S639G KI mice. Our results provide the first glimpse of global changes in gene expression at the protein level associated with the RBM20 S637A and S639G missense mutations.