Genotype control of the dystrophia muscularis gene in mice

Abstract

MUTANTS of the dystrophia muscularis gene (dy) in mouse suffer from progressive skeletal muscle loss, together with inadequate repair or regeneration⁶. In 1974 I reported a distinctive phenotypic difference between two dystrophic mutant alleles with respect to myogenesis in vitro¹. Homozygous dy^2J mice gave cultures in which there was apparently normal myogenesis, whereas mice homozygous for dy gave cultures which contained large numbers of grouped uninucleate myoblasts (pseudostraps) in place of multinucleate syncitial myotubes². MacPike, however, showed³ that muscular dystrophies caused by these two alleles carried in the same genetic background (C57BL/6J) were similar when assessed histologically. I have, therefore, investigated how the process of myogenesis in vitro (which can be considered to be another independent function of the muscle) is affected not only by the two allelic mutants but also by the genetic background. The dy dystrophy was known to be histologically similar in either the C57BL/6J or 129/ReJ background³ but surprisingly C57BL/6J dy/dy cultures gave normal myogenesis while 129/ReJ dy/dy cultures again produced pseudostraps.