We isolated 10 myoblast clones from Syrian/golden hamster embryo (SHE) cells irradiated with ultraviolet light. They were originally isolated as anchorage-independent clones. All clones showed characteristic morphology of myoblast in culture and formed swirled myofiber colonies specific to myoblast macrocolonies. However, in immunostaining experiments using anti-fast myosin antibody, we found that 4 of 10 myoblast clones were myosin negative (Myo-), while six were myosin positive (Myo+). Western blot analysis confirmed the disappearance of the 200-kDa myosin-specific band in the 4 Myo-clones. Furthermore, these 4 Myo-clones lost the ability to form multinucleated myotubes. Karyotype analysis revealed that all Myo-clones had trisomy of chromosome 7, while Myo+clones showed no apparent karyotypic change from normal SHE cells. Compared with that of SHE cells, the transcriptional level of the myc gene in Myo+clones was augmented, but there was no increase of myc gene expression in Myo-clones. Furthermore, the introduction of activated myc gene partially converted the Myo-phenotype to Myo+. These results suggest that trisomy of chromosome 7 and a deficiency in enhanced expression of the myc oncogene are associated with the suppression of both the production of myosin and the formation of multinucleated cells. © 1991.
Suzuki, K., Suzuki, F., Nikaido, O., & Watanabe, M. (1991). Suppression of differentiation phenotypes in myogenic cells: Association of aneuploidy and altered regulation of c-myc gene expression. Experimental Cell Research, 195(2), 416–422. https://doi.org/10.1016/0014-4827(91)90392-8