EVIDENCE FOR IMPLICATION OF MUSCLE-SPECIFIC CALPAIN (P94) IN MYOFIBRILLAR INTEGRITY

The expression and the putative function(s) of a specific muscle calci um-dependent protease were investigated during myogenesis using rat my oblast primary cultures as a model. We have shown that the levels of p 94 mRNAs increase as a function of myoblast differentiation, with the greatest amount of these RNAs being present during the later stages (8 th day after plating). After an antisense oligodeoxyribonucleotide tre atment with p94, ultrastructural studies show dramatic perturbations i n differentiated myotubes and during myofibrillogenesis, mainly involv ing myofibrillar stability and Z-line integrity. These results may be related to recent findings about the role of p94 gene mutations in lim b-girdle muscular dystrophy type 2A.