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 gamma chain isoform laminin， gamma 1. The gamma 1 chain， formerly thought to be a beta chain， contains structural domains similar to beta chains， however， lacks the short alpha region separating domains I and II. The structural organization of this gene also suggested that it had diverged considerably from the beta chain genes. Embryos of transgenic mice in which both alleles of the gamma 1 chain gene were inactivated by homologous recombination， lacked basement mem