THE HUMAN LAMININ BETA-2 CHAIN (S-LAMININ) - STRUCTURE, EXPRESSION INFETAL TISSUES AND CHROMOSOMAL ASSIGNMENT OF THE LAMB2 GENE

The sequence of the human laminin beta 2 chain (previously s-laminin) was derived from cloned cDNAs. The complete translation product has 17 98 amino acid residues, including a 32-residue signal peptide. The hum an chain lacks the tripeptide sequence LRE in domain I which is presen t in the rat polypeptide chain and has been shown to promote motor neu ronal cell adhesion. The human gene (LAMB2) was localized to chromosom e 3p21 using somatic cell hybrids and fluorescent in situ hybridizatio n analysis. Northern and in situ hybridization analyses from numerous fetal tissues revealed that the beta 2 chain is generally widely expre ssed. beta 2, but not beta 1, was shown by in situ hybridization to be expressed in fetal brain and renal glomeruli. In fetal skin, beta 2 w as expressed both in epidermal and dermal cells, while beta 1 was expr essed only in the dermis. Expression of beta 2 in fetal liver was seen in hepatocytes, while no signals were observed for beta 1. In lung, b oth beta 1 and beta 2 were expressed in alveoli and bronchial smooth m uscle cells, whereas only the beta 2 chain was expressed in bronchial epithelial cells. In striated muscle, however, the beta 1 chain, but n ot beta 2, was expressed. These results indicate different biological roles for the laminin beta 1 and beta 2 chains.