Figure 5

Not all tissues receiving notochord-emitted signals are affected by U0126 treatment. A-D: flk-1 expression reveals defects in dorsal aorta differentiation (green arrow in panel D) and in the sprouting of intersomitic vessels. Notice that both lack of sprouting (yellow arrows) and double sprouting (red arrow) occurs in U0126-treated embryos (D). Expression of the early muscle differentiation marker myoD is normal in treated embryos (E, F) but the muscle pioneer cell marker eng2 is upregulated (G, H). The floor plate of the neural tube differentiates normally (I, J and also Fig. 4/M–X). Isl-1 expression shows that the sensory Rohon-Beard neurons and motoneurons both develop properly in treated embryos (K, L)