OTUD6B Is Essential for Heart Development and Cardiac Function

Ubiquitin (Ub)-dependent proteolysis is essential for protein homeostasis, and its disruption is increasingly recognized as a pathogenic driver of cardiomyopathy and heart failure. Deubiquitinases (DUBs) counterbalance ubiquitination by removing Ub from substrate proteins, thereby modulating diverse cellular processes. However, the specific roles of individual DUBs in cardiac biology remain largely undefined. This project investigates the cardiac function of OTUD6B, a member of the OTU (Ovarian Tumor) DUB family implicated in cell-cycle control, apoptosis, inflammation, DNA repair, and tumorigenesis. Human OTUD6B variants are associated with intellectual disability and congenital heart defects, yet its mechanistic roles in the heart have remained unexplored. We demonstrate for the first time that OTUD6B is essential for perinatal ventricular development and adult cardiac homeostasis. Mice with germline Otud6b deletion exhibited ventricular septal defects, biventricular wall thinning, and perinatal lethality. Transcriptomic and biochemical analyses revealed defects in cardiomyocyte cell-cycle progression, potentially through dysregulation of cell-cycle regulators such as Cyclin E. To define cardiomyocyte-autonomous functions and assess roles beyond development, we generated cardiomyocyte-specific OTUD6B knockout (CKO) mice (αMHC-Cre). While cardiac function was preserved at 3 months, CKO mice developed reduced ejection fraction by 4 months and progressed to severe dilated cardiomyopathy, myocardial fibrosis, and heart failure by 7 months. Transcriptomic profiling of CKO hearts prior to overt disease uncovered broad suppression of pathways related to oxidative phosphorylation, fatty acid metabolism, and cardiac contraction. GSEA revealed significant downregulation of mitochondrial gene programs. In cultured cardiomyocytes, silencing Otud6b impaired mitochondrial respiration, increased mitochondrial ROS, and markedly reduced CCCP-induced mitochondrial ubiquitination, accompanied by destabilization of PINK1 and Parkin—key regulators of mitophagy. These findings identify OTUD6B as a critical regulator of mitochondrial quality control. To evaluate the pathogenic role of human OTUD6B mutations, we generated a cardiomyocyte-specific knock-in (CKI) model expressing the disease-associated R116* truncation mutant (αMHC-Cre/+:Otud6bKI/flox). CKI mice recapitulated the progressive cardiomyopathy and heart failure phenotype of CKO mice, supporting a causal role for this mutation. In summary, our work establishes OTUD6B as a key regulator of heart development and adult cardiac function, acting in part through maintenance of mitochondrial homeostasis and quality control. These findings further suggest that individuals carrying OTUD6B loss-of-function variants may face elevated cardiovascular risk. The CKI model also provides a powerful platform for mechanistic studies and for developing therapeutic strategies to treat OTUD6B-associated cardiac disease. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.