Fig. 4. Upregulation of cyclin D1 is a conserved activity of the Msx family. (A) C2C12 cells were infected with a control retrovirus (Vector) or retroviruses expressing the indicated homeoproteins and grown under conditions that promote differentiation. Scale bar: 0.1 mm. (B) Western blot analysis was performed using extracts prepared from C2C12 cells infected with a control retrovirus (Vector) or with retroviruses expressing the indicated homeoproteins, as in A. The panels show whole cell extracts probed with the indicated antibodies. Equivalent expression of the various homeoproteins is shown by -Myc, which detects the Myc epitope present at the N-terminal region of each homeoprotein. RNA polymerase II (-RNA PolII) is a control for protein loading.