Integrated proteomics and transcriptomics analysis reveals insights into differences in premature mortality associated with disparate pathogenic RBM20 variants

Variants in RNA binding motif protein 20 (RBM20) are causative in a severe form of dilated cardiomyopathy referred to as RBM20 cardiomyopathy, yet the mechanisms are unclear. Moreover, the reason(s) for phenotypic heterogeneity in carriers with different pathogenic variants are similarly opaque. To gain insight, we carried out multi-omics analysis, including the first analysis of gene expression changes at the protein level, of mice carrying two different pathogenic variants in the RBM20 nuclear localization signal (NLS). Direct comparison of the phenotypes confirmed greater premature morality in S639G variant carrying mice compared to mice with the S637A variant despite similar cardiac remodeling and dysfunction. Analysis of differentially spliced genes uncovered alterations in the splicing of both RBM20 target genes and non-target genes, including several genes previously implicated in arrhythmia. Global proteomics analysis found that a greater number of proteins were differentially expressed in the hearts of Rbm20^S639G mice relative to WT than in Rbm20^S637A versus WT. Gene ontology analysis suggested greater mitochondrial dysfunction in Rbm20^S639G mice, although direct comparison of protein expression in the hearts of Rbm20^S639G versus Rbm20^S637A mice failed to identify any significant differences. Similarly, few differences were found by direct comparison of gene expression at the transcript level in Rbm20^S639G and Rbm20^S637A despite greater coverage. Our data provide a comprehensive overview of gene splicing and expression differences associated with pathogenic variants in RBM20, as well as insights into the molecular underpinnings of phenotypic heterogeneity associated with different dilated cardiomyopathy-associated variants.