PRESENCE OF LAMININ ALPHA-5 CHAIN AND LACK OF LAMININ ALPHA-1 CHAIN DURING HUMAN MUSCLE DEVELOPMENT AND IN MUSCULAR-DYSTROPHIES

There is currently a great interest in identifying laminin isoforms ex pressed in developing and regenerating skeletal muscle. Laminin alpha 1 has been reported to localize to human fetal muscle and to be induce d in muscular dystrophies based on immunohistochemistry with the monoc lonal antibody 4C7, suggested to recognize the human laminin alpha 1 c hain. Nevertheless, there seems to be no expression of laminin alpha 1 protein or mRNA in developing or dystrophic mouse skeletal muscle fib ers. To address the discrepancy between the results obtained in develo ping and dystrophic human and mouse muscle we expressed the E3 domain of human laminin alpha 1 chain as a recombinant protein and made antib odies specific for human laminin alpha 1 chain (anti-hLN-alpha 1G4/G5) . We also made antibodies to the human laminin alpha 5 chain purified from placenta. In the present report we show that hLN-alpha 1G4/G5 ant ibodies react with a 400-kDa laminin alpha 1 chain and that 4C7 reacts with a 380-kDa laminin alpha 5 chain. Immunohistochemistry with the h LN-alpha 1G4/G5 antibody and 4C7 revealed that the two antibodies stai ned human kidney, developing and dystrophic muscle in distinct pattern s. Our data indicate that the previously reported expression patterns in developing, adult, and dystrophic human muscle tissues with 4C7 sho uld be re-interpreted as an expression of laminin alpha 5 chain. Our d ata are also consistent with earlier work in mouse, indicating that la minin alpha 1 is largely an epithelial laminin chain not present in de veloping or dystrophic muscle fibers.