Gleneadie, H. J.; Francis, T.; Mo, S. P. L.; Ahmed, A.; Bensalah, M.; Muntoni, F.; Harridge, S. D. R.; Merkenschlager, M.; Fisher, A. G.

Background: The X-linked muscle wasting disorder Duchenne muscular dystrophy (DMD) is a progressive and ultimately fatal disease caused by loss of function mutations in the dystrophin (DMD) gene. Upregulation of utrophin (UTRN), an embryonic homologue of dystrophin, has been proposed as a therapeutic option that could ameliorate disease. We previously generated a bioluminescent screen for utrophin-upregulating compounds using a mouse reporter of endogenous utrophin expression and discovered that inhibition of ERK1/2 and EZH2, increases utrophin expression in myoblasts. Methodology: Here we extend this analysis to show that treatment of human myoblasts with the ERK1/2 inhibitor LY3214996 and the EZH2 inhibitor GSK503, increases UTRN expression in primary and immortalised myoblasts derived from healthy volunteers and DMD patients. Results: Short-term (24 hours) inhibition of ERK1/2 and EZH2 resulted in increased expression of utrophin in proliferating myoblasts. Surprisingly, in patient-derived samples, but not healthy controls, increased UTRN expression was sustained following drug removal and in vitro differentiation. Furthermore, dystrophin deficient myoblasts have altered expression of myogenic transcription factors MYOD1 and MYOG and proliferation marker Ki67, signalling an altered regenerative capacity of these cells, while ERK1/2 inhibition, alone or combined with EZH2i, reversed this transcriptional signature. Conclusions: Treatment with ERK1/2 and EZH2 inhibitors could offer a therapeutic option for DMD by increasing UTRN and MYOD1 expression. We propose that this may compensate for DMD loss and help restore productive muscle differentiation and regeneration.