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Fig. 4. Cyclopamine treatment elicits the opposite effect of shh overexpression. Stages 20, 24, 31, and 33/34 cyclopamine-treated embryos were compared to control embryos for myf-5, myoD, and pax3 expression. At stage 20, myf-5 (A, F) and myoD (K, P) expression are reduced in cyclopamine-treated embryos (F, P, arrowheads), while pax3 (W, X, b, c) is upregulated (b, c, arrows). This is especially evident in transverse sections, where pax3 expression is stronger along the lateral surface of the differentiated myotome in cyclopamine-treated embryos (c, arrow) than in controls (X). At stage 24, myf-5 (B, G) is significantly reduced in the posterior of a cyclopamine-treated embryo (G, arrowhead) when compared to a control (B). At this stage, myoD (L, Q) is reduced in the anterior–posterior extent of expression in anterior somites in cyclopamine-treated embryos (Q). Also at stage 24, pax3 expression (Y, d) is strongly upregulated in the ventral region of somites in cyclopamine-treated embryos (e, arrow). By stage 31, myf-5 expression (C–E, H–J) is strongly upregulated in the ventral domain of somites in cyclopamine-treated embryos (H–J, arrows), while initial expression in forming somites is still lost (I, arrowhead). The expression of myoD is similarly upregulated in the ventral region of somites in cyclopamine-treated embryos (R–V, arrows), particularly in posterior somites (S, arrow), and lost in the newly formed somites of the tailbud (S, arrowhead). At stage 33/34, the expression of pax3 (Z–a, e–f) remains upregulated in the ventral regions of somites in cyclopamine-treated embryos, in both the anterior (e compared to Z, arrow) and posterior (f compared to a, arrow). |
