Figure 6

Foxc2 downregulates Pax7 that stimulates myotome colonization. (A) Control GFP alone or pMIW-Pax7/GFP (B) were electroporated as in Figures 1, 2 and 3 (N = 7 and 8, respectively). At 43 hours post-treatment control cells are present in myotome (M), sclerotome and wall of the cardinal vein (CV). In contrast, Pax7+ cells are restricted to the myotome where they co-express desmin. Endothelial cells were visualized with the Qh1 antibody (blue). (C-G) Foxc2 represses Pax7 expression. (C) Control-GFP (N = 5). (D) Foxc2 was electroporated into the DM (left panel). Marked attenuation of Pax7 expression was detected at the mRNA (right panel, black bracket, N = 4) compared to the contralateral side and to GFP-control (C). (E-G) GFP-control labeled cells exhibit Pax7 immunoreactivity (E, G, arrowheads, N = 7), whereas fewer cells displayed Pax7 immunoreactivity following treatment with Foxc2 (F, G, arrows, N = 7). (G) Quantification (mean ± SEM) of cells co-expressing Pax7 protein and FoxC2-GFP. **P ≤0.01. Bar: (A-B) 30 μm; (C,D) 60 μm, (E,F) 25 μm. Des, desmin; DM, dermomyotome; EP, electroporation; ISH, in situ hybridization; SEM, standard error of the mean; SMA, smooth muscle actin; VLL, ventro-lateral lip.