Activation of Caspase-3 Apoptotic Pathways in Skeletal Muscle Fibers in Laminin α2-Deficient Mice

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dy/dy mice, which carry an unidentified mutation in the Lama2 gene, show dystrophic pathologies similar to those of human congenital muscular dystrophy. Laminin α2 deficiency induces apoptosis with DNA fragmentation. Caspases, which are involved in various types of cell death, are sequentially activated through a processing by other members of caspases. By using a cleavage site-directed antibody against caspase-3 that specifically reacts with the active form of caspase-3, we immunochemically demonstrated that caspase-3 is activated in the skeletal muscle fiber of dy/dy mice and that some of the activated caspase-3 muscle fibers are TUNEL-positive. Thus the lack of laminin α2 signals activates caspase-3, resulting in the apoptosis of muscle fibers.