Extraocular muscle is spared upon complete laminin alpha2 chain deficiency: Comparative expression of laminin and integrin isoforms.

Mutations in the gene encoding laminin (LM) alpha 2 chain cause congenital muscular dystrophy. Here, we show that extraocular muscle (EOM) is spared upon complete LM alpha 2 chain absence. The major LM chains in limb muscle basement membranes are alpha 2, beta 1, beta 2 and gamma 1 whereas alpha 2, alpha 4, beta 1, beta 2 and gamma 1 chains are expressed in EOM. Expression of LMoA chain mRNA is further increased in LM alpha 2 chain deficient EOM. Mainly integrin alpha 7X1 subunit, which binds to laminin-411, is expressed in EOM and in contrast to dystrophic limb muscle, sustained integrin OB expression is seen in LM alpha 2 chain deficient EOM. We propose that LM alpha 4 chain, possibly by binding to integrin alpha 7BX1 beta 1D, protects EOM in LM alpha 2 chain deficient muscular dystrophy. (c) 2006 Elsevier B.V./Intemational Society of Matrix Biology. All rights reserved.