THE COMPLETE CDNA SEQUENCE OF LAMININ ALPHA-4 AND ITS RELATIONSHIP TOTHE OTHER HUMAN LAMININ ALPHA-CHAINS

We previously localised the gene (LAMA4) encoding a novel]aminin alpha 4 chain to chromosome 6q21. In this study, we describe the complete c oding sequence and compare the protein with the other three known huma n laminin alpha chains. Although closely linked to LAMA2, the LAMA4 pr oduct most closely resembles laminin alpha 3, a constituent of laminin 5. Like laminin alpha 3A, the alpha 4 chain is a truncated version of the alpha 1 and alpha 2 chains, with a much reduced short arm. While the alpha 4 molecule is most similar to alpha 3, it shares some featur es of the C-terminal domains G4 and G5 in common with alpha 2. Unlike the LAMAS gene, LAMA4 appears to encode only a single transcript, as d etermined by 5' rapid amplification of cDNA ends. The cDNA sequence en codes 1816 amino acids. which include a 24-residue signal peptide. The gene is expressed in skin, placenta, heart, lung, skeletal muscle, an d pancreas. We have also shown that the mRNA can be readily reverse tr anscribed and amplified from cultured dermal fibroblasts.