Laminin , an extracellular protein , is a major component of the basement membrane. It is thought to mediate the attachment , migration , and organization of cells into tissues during embryonic development by interacting with other extracellular matrix components. It is composed of three subunits , alpha , beta , and gamma , which are bound to each other by disulfide bonds into a cross-shaped molecule. This gene encodes the alpha 2 chain , which constitutes one of the subunits of laminin 2 (merosin) and laminin 4 (s-merosin) . Mutations in this gene have been identified as the cause of congenital merosin-deficient muscular dystrophy. Two transcript variants encoding different proteins have been found for this gene.