Fig. 5.

Wnt and Sox2 pattern midline tissues independently of Notch activity. (A-L) Loss of Wnt signaling and overexpression of sox2 using stable transgenic lines causes the notochord domain of col2a1 expression to be lost in the tail (A,C,E), whereas the floor plate marker foxa2 shows enhanced expression (G,I,K). Combining DAPT treatment with these conditions immediately after the heat shock has no effect on notochord patterning (B,D,F) but does reduce foxa2 expression (H,J,L). (M-P) Blocking Wnt signaling results in ectopic sox2 expression throughout the tailbud (M,N). This effect is independent of active Notch signaling (O,P). (Q) A fate map of MPCs (see text for details) indicates that floor plate cells are exclusively derived from a dorsal MPC population (blue), whereas hypochord (green) is derived only from a ventral MPC population. Cells are false colored based on fate; horizontal lines indicate the boundary of the notochord.