FIGURE 4.

Roles of β-catenin, Meox1, and Pax3 in rexinoid-enhanced skeletal myogenesis. A, a clone of P19 cells expressing a dominant negative β-catenin (β-cat/EnR) was differentiated with bexarotene (BEX, 100 nm) or RA (10 nm) and stained for myosin heavy chain (MyHC) and MyoD. Cells harboring the empty vector were used as control. Quantification is plotted as fractions of cells differentiated into skeletal myocytes. Error bars are the S.D. of three independent experiments. Western blot analysis was used to determine myogenin expression with undifferentiated ES cells as control. B, the representative images of myosin heavy chain and MyoD costaining. C, cells expressing the dominant negative Meox1 (Meox1/EnR) or Pax3 (Pax3/EnR) were differentiated as in A. **, p < 0.01. Cells harboring the empty vector were used as control. Error bars are the S.D. of four independent experiments. D, the relative mRNA levels of EnR were determined by quantitative real-time RT-PCR and plotted as fold difference in relation to untreated day 4 controls after being normalized to GAPDH.