The most common form of human congenital muscular dystrophy (CMD) is caused by mutations in the laminin-α2 gene. Loss of laminin-α2 function in this autosomal recessive type 1A form of CMD results in neuromuscular dysfunction and, often, early death. Laminin-α2–deficient skeletal muscles in both humans and mice show signs of muscle cell death by apoptosis. To examine the significance of apoptosis in CMD1A pathogenesis, we determined whether pathogenesis in laminin-α2–deficient (Lama2–/–) mice could be ameliorated by inhibiting apoptosis through either (a) inactivation of the proapoptosis protein Bax or (b) overexpression of the antiapoptosis protein Bcl-2 from a muscle-specific transgene. We found that both of these genetic interventions produced a several-fold increase in the lifespan of Lama2–/– mice. Bax inactivation also improved postnatal growth rate and myofiber histology and decreased fixed contractures of Lama2–/– mice. Thus, Bcl-2 family–mediated apoptosis contributes significantly to pathogenesis in the mouse model of CMD1A, and antiapoptosis therapy may be a possible route to amelioration of neuromuscular dysfunction due to laminin-α2 deficiency in humans.
Mahasweta Girgenrath, Janice A. Dominov, Christine A. Kostek, Jeffrey Boone Miller