Gmppb-mutant mice exhibit dystroglycanopathy symptoms that are rescued with GSK3β inhibition or AAV-mediated GMPPB gene replacement.

Mutations in GDP-mannose pyrophosphorylase B (GMPPB) cause dystroglycanopathy, a rare neuromuscular disorder characterized by α-dystroglycan hypoglycosylation, yet the pathogenic mechanisms and therapeutic options remain poorly defined. To dissect the molecular basis of dystroglycanopathy, we generate Gmppb knockout and knock-in (P32L and R287Q) mice. We show that homozygous Gmppb knockout and P32L mutant mice (both male and female) display embryonic lethality, while heterozygous Gmppb-P32L (GmppbP32L/+) mice (both male and female) develop progressive muscular dystrophy accompanied by Purkinje cell loss, peripheral demyelination, and impaired nerve conduction. Integrated biochemical, transcriptomic, metabolomic and glycoproteomic analyses reveal widespread protein hypoglycosylation, metabolic dysregulation and suppressed Wnt/β-catenin signaling, resulting in defective differentiation and regeneration of muscle stem cells. Pharmacological activation of Wnt signaling with CHIR-99021 restores myogenic capacity and improves regeneration after injury. Furthermore, AAV-mediated GMPPB gene replacement reinstates α-dystroglycan glycosylation, normalizes GDP-mannose levels, and rescues motor and electrophysiological defects. Collectively, our findings establish GmppbP32L/+ mice as a faithful model of GMPPB-associated dystroglycanopathy and demonstrate that Wnt pathway activation and AAV-based gene therapy represent promising strategies for treating glycosylation-defective muscular dystrophies.