Evidence for implication of muscle-specific calpain (p94) in myofibrillar integrity.

The expression and the putative function(s) of a specific muscle calcium-dependent protease were investigated during myogenesis using rat myoblast primary cultures as a model. We have shown that the levels of p94 mRNAs increase as a function of myoblast differentiation, with the greatest amount of these RNAs being present during the later stages (8th day after plating). After an antisense oligodeoxyribonucleotide treatment with p94, ultrastructural studies show dramatic perturbations in differentiated myotubes and during myofibrillogenesis, mainly involving myofibrillar stability and Z-line integrity. These results may be related to recent findings about the role of p94 gene mutations in limbgirdle muscular dystrophy type 2A.