DAG1 encodes dystroglycan 1, a transmembrane glycoprotein component of the dystrophin-glycoprotein complex (DGC) that serves multiple critical functions in skeletal and cardiac muscle 1. Structurally, dystroglycan 1 acts as an adhesion molecule linking the actin cytoskeleton to the extracellular matrix via basement membrane interactions 1. Beyond structural roles, DAG1 functions as a receptor for pathogenic arenaviruses (Lassa virus, lymphocytic choriomeningitis virus) and serves as a Schwann cell receptor for Mycobacterium leprae in leprosy pathogenesis [UniProt sources]. DAG1 participates in Hippo pathway regulation by directly binding the effector protein Yap to inhibit cardiomyocyte proliferation, linking the DGC to developmental growth control 1. Biallelic DAG1 mutations cause severe muscular dystrophy-dystroglycanopathy with congenital brain and eye anomalies, characterized by deficient alpha-dystroglycan glycosylation 23. Heterozygous DAG1 truncating variants cause isolated or pauci-symptomatic hyperCKemia (elevated serum creatine kinase), with Western blot analysis confirming reduced beta-dystroglycan expression in affected muscle 4. DAG1 expression is regulated at multiple levels including transcriptional control via Sp1 transcription factor binding, DNA methylation, and histone acetylation during myogenic differentiation 5. Recent findings reveal DAG1 promotes fibroblast-keratinocyte interactions in skin wound healing via HSPG2-DAG1 ligand-receptor pairing 6, expanding its functional repertoire beyond muscle.