The Laminin a Chains: Expression, Developmental Transitions, and Chromosomal Locations of a 1-5, Identification of Heterotrimeric Laminins 8–11, and Cloning of a Novel a 3 Isoform

Using a panel of nucleotide and antibody probes, we surveyed the expression of a 1-5 in murine tissues. All five chains were expressed in both embryos and adults, but each was distributed in a distinct pattern at both RNA and protein levels. Overall, a 4 and a 5 exhibited the broadest patterns of expression, while the expression of a1 was the most restricted. Detailed analysis of developing kidney revealed that some individual basal laminae, including those of the tubule and glomerulus, changed in laminin chain composition as they matured. During glomerulogenesis there are developmental transitions in laminin trimer deposition. Initially the GBM contains laminin-111, laminin-411 and laminin-511. By the capillary loop stage during GMB maturation, laminin-111 is eliminated from the GBM and the beta 2 chain begins to accumulate while the beta 1 chain is down-regulated.