Spontaneous muscular dystrophy caused by a retrotransposal insertion in the mouse laminin alpha2 chain gene.

We identified a novel spontaneous mouse model of human congenital muscular dystrophy with laminin alpha2 chain deficiency, named dy(Pas)/dy(Pas). Homozygous animals rapidly developed a progressive muscular dystrophy leading to premature death. Immunohistological and biochemical analyses demonstrated the absence of laminin alpha2 chain expression in skeletal muscle. Analysis of the laminin alpha2 chain cDNA showed the insertion of the long terminal repeat of an intracisternal A-particle gene. In addition, a 6.1 kb insertion composed of retrotransposon elements was identified in the Lama2 sequence. The dy(Pas)/dy(Pas) mouse is thus the first spontaneous mutant with a complete laminin alpha2 chain deficiency in which the mutation has been identified.