TEMPORALLY DISTINCTIVE CHANGES OF ALTERNATIVE SPLICING PATTERNS DURING MYOGENIC DIFFERENTIATION OF C2C12 CELLS

It is well known that skeletal muscle differentiation is accompanied b y the appearance of many muscle-specific components and that some of t hese components are generated through muscle-specific alternative spli cing, It is not clear, however, in what manner, including timing, the system that regulates the muscle-specific splicing reactions is constr ucted during the process of myogenic differentiation. We simultaneousl y examined the changes in several splicing patterns for the neural cel l adhesion molecule (NCAM), beta-tropomyosin, and M-type pyruvate kina se genes during myogenic differentiation of cultured myoblasts using t he reverse transcription-polymerase chain reaction method. The NCAM gl ycosylphosphatidylinositol 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 sta rted and abruptly increased at about the time when cell-fusion appeare d. M2-type pyruvate kinase was gradually substituted for the M1-type m olecule, Skeletal muscle-type beta-tropomyosin was predominantly selec ted even in myoblasts in the growth medium, As a result, each transcri pt of these genes independently showed a temporally distinctive patter n of change in isoform selection during the myogenic differentiation o f C2C12 cells. These observations suggest that some independent regula tion of alternative splicing reactions should occur during myogenic di fferentiation.