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 in vitro myogenic potential of BMD myogenic cells, as well as in vitro and in vivo studies to evaluate the therapeutic efficacy of three candidate molecules targeting dystrophin ubiquitination pathway. In vitro 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. In vivo 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.