Differential expression of C-protein isoforms in developing and degenerating mouse striated muscles

With the aim of clarifying the roles of C-protein isoforms in developing ma mmalian skeletal muscle, we cloned the complementary DNA (cDNAs) encoding m ouse fast (F) and slow (S) skeletal muscle C-proteins and determined their entire sequences. Northern blotting with these cDNAs together with mouse ca rdiac (C) C-protein cDNA was performed. It revealed that in adult mice, C, F, and S isoforms are expressed in a tissue-specific fashion, although the messages for both F and S isoforms are transcribed in extensor digitorum lo ngus muscle, which has been categorized as a fast muscle. In addition, alth ough C isoform is expressed first and transiently during development of chi cken skeletal muscles, C isoform is not expressed in mouse skeletal muscles at all through the developmental stages; S isoform is first expressed, fol lowed by the appearance of F isoform, Finally, in dystrophic mouse skeletal muscles, the expression of S isoform is increased as it is in dystrophic c hicken muscle, These observations suggest that mutations in C isoform (MyBP -C) do not lead to any disturbance in skeletal muscle, although they may le ad to familial hypertrophic cardiomyopathy. We also suggest that the expres sion of S isoform may be stimulated in degenerating human dystrophic muscle s. (C) 1999 John Wiley & Sons, Inc.