Expression of the c-ski proto-oncogene during cell cycle arrest and myogenic differentiation

Although the ski oncogene plays a role in cell proliferation, morphological transformation, and myogenic differentiation, the myogenic activities of the proto-oncogene c-ski have yet to be elucidated. c-ski is expressed within myoblasts during embryogenesis. Transcripts from the proto-oncogene can be detected in somites early in myogenic commitment, as well as in terminally differentiated skeletal muscle. However, c-ski mRNAs expressed in cells of the myogenic lineage are indistinguishable from c-ski transcripts in other cell types, raising the possibility that muscle-specific c-ski transcripts are expressed transiently. Avian cell lines QM7 and QM5 were used as a model to analyze changes in expression and alternative exon usage of c-ski during synchronous muscle differentiation. Upon serum deprivation, QM7 cells undergo myogenic differentiation. In contrast, QM5 cells cease proliferation but do not differentiate. Results show that levels of expression and alternative splicing of c-ski transcripts remain unchanged during cell cycle arrest or myogenic differentiation.