Ubiquitination-targeted therapies improve BMD iPSC myogenic cell engraftment and dystrophin expression in vivo

Becker muscular dystrophy (BMD) is caused by in-frame mutations in dystrophin gene, leading to progressive muscle weakness, and cardiac and respiratory complications. Currently, there is no cure. We have recently identified the importance of poly-ubiquitination in regulating dystrophin stability through the binding of lncRNA H19 to the dystrophin C-terminal zinc-finger domain (ZNF), inhibiting TRIM63-mediated poly-ubiquitination. We also demonstrated that BMD mutations lead to conformational changes in ZNF domain, reduced lncRNA H19 binding and increased dystrophin ubiquitination. Here we used BMD iPSCs to investigate the <i>in vitro</i> myogenic potential of BMD myogenic cells, as well as <i>in vitro</i> and <i>in vivo</i> studies to evaluate the therapeutic efficacy of three candidate molecules targeting dystrophin ubiquitination pathway. <i>In vitro</i> assays indicated significant deficiencies in myogenic cell differentiation of BMD iPSCs, including reduced proliferation, cell-cycle arrest, increased apoptosis, senescence, and membrane damage, and impaired myotube formation. <i>In vivo</i> engraftment demonstrated significant improvement in BMD iPSC myogenic cell survival and dystrophin expression in the animals treated with two molecules: a TRIM63 inhibitor and an α-synuclein aggregation inhibitor. These findings provide promising evidence for the potential therapeutic efficacy of these ubiquitination pathway inhibitors to improve muscle progenitor cell survival and dystrophin expression in BMD patients.