Simultaneous overexpression of Oct4 and Nanog abrogates terminal myogenesis

Oct4 and Nanog are two embryonic stem (ES) cell-specific transcrip-tion factors that play critical roles in the maintenance of ES cell pluripotency. In this study, we investigated the effects of Oct4 and Nanog expression on the differentiation state of myogenic cells, which is sustained by a strong positive feedback loop. Oct4 and Nanog, either independently or simultaneously, were overexpressed in C2C12 myoblasts, and the expression of myogenic lineage-specific genes and terminal differentiation was observed by RT-PCR. Overexpression of Oct4 in C2C12 cultures repressed, while exogenous Nanog did not significantly alter C2C12 terminal differentiation. The expression of Pax7 was reduced in all Oct4-overexpressing myoblasts, and we identified a major Oct4-binding site in the Pax7 promoter. Simulta-neous expression of Oct4 and Nanog in myoblasts inhibited the formation of myotubes, concomitant with a reduction in the endoge-nous levels of hallmark myogenic markers. Furthermore, overexpres