Defects include those in genes and protein products associated with the sarcolemma (dystrophin deficient X-linked muscular dystrophy and sarcoglycan-deficient limb–girdle muscular dystrophy) and with the extracellular matrix (collagen 6, laminin α2, and α-dystroglycan-deficient congenital muscular dystrophies). Here, DAG1 is linked to congenital muscular dystrophy.