Background：

Laminins， a family of extracellular matrix glycoproteins， are the major noncollagenous constituent of basement membranes. They have been implicated in a wide variety of biological processes including cell adhesion， differentiation， migration， signaling， neurite outgrowth and metastasis. Laminins， composed of 3 non identical chains: laminin alpha， beta and gamma . Some of the chains have been shown to differ with respect to their tissue distribution， presumably reflecting diverse functions in vivo. This gene encodes the beta chain isoform laminin， beta 2. The beta 2 chain contains the 7 structural domains typical of beta chains of laminin， including the short alpha region. However， unlike beta 1 chain， beta 2 has a more restricted tissue distribution. It is enriched in the basement membrane of muscles at the neuromuscular junctions， kidney glomerulus and vascular smooth muscle. Transgenic mice in which the beta 2 chain gene was inactivated by homologous recombination， showed defec