Disease modeling and gene correction of LGMDR21- iPSCs elucidates the role of POGLUT1 in skeletal muscle maintenance, regeneration and satellite cell niche
LGMDR21 is a recessive limb girdle muscular dystrophy caused by mutations in the protein O-glucosyltransferase 1 gene (POGLUT1). This enzyme is responsible for O-glucosylation of specific epidermal growth factor-like (EGF) repeats found in ~50 mammalian proteins, including the Notch receptors. Previous data from patient biopsies indicated impaired Notch signaling, reduction of muscle stem cells and accelerated differentiation of myoblasts as possible pathologic mechanism. Using patient iPSCs and their corrected isotypes, we showed that patient iPSC-derived myogenic progenitors demonstrate dysregulation of gene clusters related to POGLUT1, NOTCH, muscle development, ECM, cell adhesion and migration (MET signaling). They also exhibited reduced in vitro enzymatic activity and NOTCH signaling, defective myogenesis, proliferation, migration and differentiation. In vivo studies demonstrated significant reductions in engraftment, muscle stem cell formation, PAX7 expression and maintenance, along with increased percentage of PAX7 positive cells in the interstitial space between myofibers. Remarkably, gene corrected cells were able to rescue in vitro and in vivo phenotypes. These results describe novel mechanistic insights for LGMDR21 pathology and the efficacy of site-specific gene correction in disease modeling and rescue of the phenotypes and paving the way toward gene therapies for LGMDs. Overall design: NOT PROVIDED; REQUESTED