Abstract
We have determined the structural organization of the human and mouse genes that encode the laminin beta2 chain (s-laminin), an essential component of the basement membranes of the neuromuscular synapse and the kidney glomerulus. The human and mouse genes have a nearly identical exon-intron organization and are the smallest laminin chain genes characterized to date, due to the unusually small size of their introns. The laminin beta2 chain genes of both species consist of 33 exons that span </=12 kilobase pairs of genomic DNA. The exon-intron pattern of the laminin beta2 chain gene is also highly similar to that of the human genes encoding the homologous laminin beta1 and beta3 chains. The putative promoter regions of the human and mouse laminin beta2 chain genes have features characteristic of the promoters of genes that have a limited tissue expression. Considerable conservation of the intron sequences of the mouse and human genes was observed. The first intron of the human gene, located 1 base pair upstream of the translation start codon, contains a non-consensus 5' splice site. This intron was shown to be inefficiently spliced in humans, suggesting that post-transcriptional mechanisms may be involved in the regulation of laminin beta2 chain gene expression.
Highlights
Basement membranes in different tissues perform a variety of functions, including the filtration of macromolecules and the anchorage of epithelial cells to the underlying stroma [1]
We have shown that the laminin 2 chain and adhalin are deficient in the skeletal muscle basement membrane of two individuals with the autosomal recessive disease Walker-Warburg syndrome
We have characterized the human and mouse genes that encode the laminin 2 chain, both of which were found to consist of 33 exons that occupied only 12 kb or less of genomic DNA
Summary
Basement membranes in different tissues perform a variety of functions, including the filtration of macromolecules and the anchorage of epithelial cells to the underlying stroma [1]. Heterogeneity in basement membrane structure and function may be mediated in large part by tissue-specific variations in the expression pattern of the subunits of the two main components, laminin and type IV collagen. The ␣ chains contain an additional C-terminal globular domain of approximately 100 kDa. The laminin chains can assemble into at least seven different laminin isoforms [4] that have distinct tissue distributions (8 –9). Laminin 2 Chain Gene Structure lar junctions [26] and developed massive proteinuria due to impaired filtration by the glomerular basement membrane [27]
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