A POGLUT1 mutation causes a muscular dystrophy with reduced notch signaling and satellite cell loss

Abstract

Skeletal muscle regeneration by muscle satellite cells is a physiological mechanism activated upon muscle damage and regulated by Notch signaling. In a family with autosomal recessive limb-girdle muscular dystrophy, we identified the D233E missense mutation in POGLUT1 (protein O-glucosyltransferase 1), an enzyme involved in notch posttranslational modification and function. In vitro and in vivo experiments demonstrated that the mutation reduces O-glucosyltransferase activity on notch and impairs muscle development. Muscles from patients revealed decreased notch signaling, dramatic reduction of satellite cell pool and a muscle-specific α-dystroglycan hypoglycosylation not present in patients' fibroblasts. Primary myoblasts from patients showed slow proliferation, facilitated differentiation and a decreased pool of quiescent PAX7+ cells. None of these alterations were found in muscles from secondary dystroglycanopathy patients. We generated two different continuous myogenic cell lines with the D233E mutation, which reproduced the same phenotypic features displayed by the primary myoblasts during proliferation/differentiation and showed α-dystroglycan hypoglycosylation during differentiation. NICD1 overexpression by lentiviral infection fully rescued the phenotype. In addition, inhibition of notch on C2C12 culture under differentiation by DAPT led to reduced level of α-dystroglycan and disrupted its pattern of glycosylation. These data suggest that notch-dependent loss of satellite cells is a key pathomechanism for this novel form of muscular dystrophy.