Fig. 3

Cell fate distributions are affected by changes in Wnt signaling or sox2 overexpression. (A-H) Cells from stable transgenic donors (A-D) or from transiently transgenic donors (E-H) were transplanted into wild-type hosts and transgene expression induced after the completion of gastrulation (bud stage). (I-J′) In some cases, host embryos were stained by fluorescent in situ hybridization for col2a1 expression (green) and imaged by confocal microscopy. Transplanted cells are in red. A maximum projection image (I,J) and digital transverse section (I′,J′) reveal the precise midline position of transplanted cells from control (I,I′) and hsp70l:TCFΔC-GFP (J,J′) transplanted cells. (K) The contribution of transient transgenic cells to floor plate, notochord and hypochord was quantitated (raw data and statistics are provided in Table 1). Blocking Wnt signaling (B,F,J,J′) expanded the floor plate contribution at the expense of notochord, and activating Wnt had the opposite effect (C,G). Overexpression of sox2 (D,H) produced an effect very similar to blocking Wnt. Cell fate changes are statistically significant (see Table 1). Green, red and blue arrowheads indicate notochord, hypochord and floor plate, respectively.