Promotes matrix assembly (By similarity). Involved in the organization of skeletal muscles and in the formation of neuromuscular junctions (Probable). {ECO:0000250|UniProtKB:Q8R2Z5, ECO:0000305|PubMed:33559681}. This is the function of VWA1 (von Willebrand factor A domain containing 1, ENSG00000179403).