Decreased expression of laminin beta 1 in chromosome 21-linked Bethlem myopathy

Muscle biopsies of four patients affected by chromosome 21-linked Bethlem m yopathy were investigated by means of immunohistochemistry, with monoclonal antibodies for laminin chains, dystrophin and dystrophin associated glycop roteins. The objective of this study was to determine whether an altered mo lecular structure of collagen type VI, characteristic of Bethlem myopathy, could influence the expression of the protein complex linking the extracell ular matrix with the subsarcolemmal cytoskeleton. Normal expression of all proteins was found except for laminin beta 1, along with an age related pro gressive deficiency of this protein in the muscle fibre basal lamina. This study shows that Bethlem myopathy linked to chromosome 21 is associated wit h a secondary decrease in laminin beta 1 expression. (C) 1999 Elsevier Scie nce B.V. All rights reserved.