Temporally distinctive changes of alternative splicing patterns during myogenic differentiation of C2C12 cells.

It is well known that skeletal muscle differentiation is accompanied by the appearance of many muscle-specific components and that some of these components are generated through muscle-specific alternative splicing. It is not clear, however, in what manner, including timing, the system that regulates the muscle-specific splicing reactions is constructed during the process of myogenic differentiation. We simultaneously examined the changes in several splicing patterns for the neural cell adhesion molecule (NCAM), beta-tropomyosin, and M-type pyruvate kinase genes during myogenic differentiation of cultured myoblasts using the reverse transcription-polymerase chain reaction method. The NCAM glycosylphosphatidylinositol anchor form increased in preference to the transmembrane form immediately after the induction of differentiation, while the selection of NCAM MSD1 (muscle-specific domain 1) exons started and abruptly increased at about the time when cell-fusion appeared. M2-type pyruvate kinase was gradually substituted for the M1-type molecule. Skeletal muscle-type beta-tropomyosin was predominantly selected even in myoblasts in the growth medium. As a result, each transcript of these genes independently showed a temporally distinctive pattern of change in isoform selecting during the myogenic differentiation of C2C12 cells. These observations suggest that some independent regulation of alternative splicing reactions should occur during myogenic differentiation.