Fig. 2

Fig. 2

Wnt Signaling Is Cell-Autonomously Required for Tail Bud Stem Cells to Join Somites throughout Body Formation (A and B) Experimental design for cell-transplants examining the pregastrula (A) and postgastrula (B) requirements for Wnt signaling. (C and D) Fluorescein dextran labeled donor cells were transplanted into the ventral margin of shield stage unlabeled wild-type host embryos. (C) Control cells contribute normally to posterior somites. (D) Cells from HS:TCFΔC donor embryos heat-shocked at the pregastrula (dome) stage before transplantation are unable to contribute to somites, and instead reside within the neural tube. (E) Double transplantation of wild-type (red) and HS:TCFΔC (green) cells that were heat-shocked at dome stage and cotransplanted into the ventral margin of wild-type host embryos. Wild-type cells contribute normally to somites whereas cells lacking Wnt function cannot join the posterior somites and instead contribute to the neural tube. (F) Host embryos containing fluorescein dextran labeled HS:TCFΔC cells transplanted into the ventral margin and heat-shocked at the postgastrula (bud) stage have an intermediate phenotype, with anterior cells contributing normally to somites (arrow) and posterior cells transfating to neural tissue (arrowheads). (G–R) The ability of transplanted cells to differentiate into muscle or neurons was verified using antibodies directed against Myosin Heavy Chain or Elavl, respectively. (G–L) Wild-type cells labeled with fluorescein dextran (green) transplanted into the ventral margin of unlabeled wild-type host embryos and heat-shocked at bud stage primarily form muscle (L) with the occasional differentiated neuron (I, arrow), as indicated by the overlap of red fluorescent antibody staining and the green fluorescence of the transplanted donor cells. (M–R) HS:TCFΔC cells labeled with fluorescein dextran were transplanted into unlabeled wild-type host embryos and heat-shocked at bud stage. Transplanted cells in the posterior of the embryo differentiated as neurons (O) and not muscle (not shown), whereas the early differentiating cells in the anterior regions contributed to muscle (R). See also Figures S2 and S3.