Fig. 3. MyoD is unable to upregulate expression of p27^Xic1 in vivo. (A) Quantitative RT-PCR for MA, p27^Xic1 and ODC on cDNA from animal caps of embryos injected with 100 pg MyoD. (B-F') Embryos were injected with 100 pg MyoD (B,C,F,F') or 50 pg DNMyoD (D,E) into one cell of two-cell stage embryos, along with ß-gal as a tracer (light blue, injected side towards the left in B-E or upwards in F,F'). Dorsal views of embryos analyzed for (B,D) MA or (C,E) p27^Xic1 expression by whole-mount in situ hybridization at stage 15 (F,F'). (F,F') MyoD-injected embryos allowed to develop to stage 21 were stained for phospho-histone-H3 then longitudinally sectioned and stained for MA (red) and Hoechst (blue, DNA specific). MyoD overexpression enlarges the area staining for MA (F) and also causes extra proliferation (F', arrows).