The Perijunctional Zone Is a Molecularly Distinct Muscle Subdomain Altered in Duchenne Muscular Dystrophy

The neuromuscular junction (NMJ) is a well-established model for synapse development, structure, and function. Surrounding the NMJ is a narrow perijunctional zone (PJZ), enriched in muscle-specific voltage-gated sodium channels that prevent synaptic fatigue. Despite this role, the PJZ remains poorly characterized. To determine its molecular composition, we engineered mice to express the biotin ligase TurboID fused to the cell adhesion molecule neurofascin (Nfasc), and that localizes to the PJZ through ankyrin scaffolding proteins. Using proximity proteomics, we identified numerous PJZ-associated proteins, including Perilipin 4 (Plin4), that were highly enriched and clustered at the PJZ. We also performed proximity proteomics on the PJZ of mdx mice, a model of Duchenne muscular dystrophy. We found broad changes in PJZ composition, including significantly reduced PJZ Plin4. These findings establish the PJZ as a molecularly distinct subdomain of skeletal muscle and provide insight into its potential roles in neuromuscular function and disease.