RNA helicase DDX5 maintains cardiac function by regulating CamkIId alternative splicing [RIP-seq]

The cardiomyocyte-specific deletion of Ddx5 in mice resulted in heart failure characterized by diminished cardiac function, enlarged heart chambers, and heightened fibrosis. Proteomic analysis unveiled the involvement of DDX5 in RNA splicing within cardiomyocytes. Our study identified DDX5 as a regulator of the abnormal splicing of CamkIId, preventing the generation of CaMKIIdA. This isoform activates LTCC through serine phosphorylation of Cacna1c, disrupting Ca2+ homeostasis. Consistently, DDX5-depleted cardiomyocytes exhibited elevated intracellular Ca2+ transients and increased sarcoplasmic reticulum Ca2+ content. Overall design: To investigate the role of DDX5 in the heart, we obtained cardiac tissues from 8-week-old DDX5fl/flMYH6Cre+ mice (mCKO), with age-matched DDX5fl/fl mouse cardiac tissues serving as controls (CTR1). Additionally, we collected cardiac tissues from Ddx5flox/flox Myh6MerCreMer mice (iCKO) after 7 days of intraperitoneal tamoxifen injection, with age-matched DDX5fl/fl mouse cardiac tissues injected with the same dose of tamoxifen serving as controls (CTR2). RNA sequencing was performed for each condition, followed by differential gene expression analysis and alternative splicing analysis against their respective controls. In addition, we conducted RNA immunoprecipitation followed by sequencing (RIP-seq) using a DDX5-specific antibody in neonatal rat cardiomyocytes.