Laminin alpha2 chain-null mutant mice by targeted disruption of the Lama2 gene: a new model of merosin (laminin 2)-deficient congenital muscular dystrophy.

Using the gene targeting technique, we have generated a new mouse model of congenital muscular dystrophy (CMD), a null mutant for the laminin alpha2 chain. These homozygous mice, designated dy3Kldy3K, are characterized by growth retardation and severe muscular dystrophic symptoms and die by 5 weeks of age. Light microscopy revealed that muscle fiber degeneration in these mice begins no later than postnatal day 9. In degenerating muscles, considerable amounts of TUNEL positive nuclei were detected as well as DNA laddering, suggesting increased apoptotic cell death was involved in the process of muscle fiber degeneration.