S-laminin: mapping to mouse chromosome 9 and expression in the linked mutants tippy and ducky.

S-Laminin, a homologue of the laminin B1 chain, is present in a subset of basal laminae, including those of the skeletal neuromuscular junction and the renal glomerulus. Here, we show that the distribution and apparent size of murine S-laminin are similar to those documented previously for rat and human. We then use interspecific backcross analysis to map the S-laminin (Lams) gene to mouse chromosome 9. Thus, it is unlinked to genes for the laminin A, B1, and B2 chains. Finally, because the Lams gene mapped near two mutations that affect neuromuscular function, ducky (du) and tippy (tip), we assayed S-laminin by Southern blotting, immunoblotting, and immunohistochemistry in these mutants. No abnormality of the S-laminin gene or protein was detectable in either mutant.