Fig. 7

Rescue of headless phenotype by transplantation of Dkk1 expressing cells. (A) Scheme describing the experimental procedures. A group of cells from sphere stage embryos injected at the one cell stage with either dkk1 plus GFP RNA or GFP RNA alone was grafted at the animal pole of gsc/foxA3 knock-down embryos either at sphere or at shield stage. Host embryos were grown up to the 2–3 somite stage and were analyzed for the expression of emx1 or grown up to 24 hpf for morphological analyses. (B–E) emx1 expression in 2–3 somite stage embryos grafted with Dkk1/GFP expressing cells (B and D) or with GFP expressing cells (C and E). Grafts performed at sphere (B and C) or shield (D and E) stages. (F–K) Embryos grafted with Dkk1/GFP expressing cells (F, H, J, K) or with GFP expressing cells (G and I) at sphere (F, G) or shield (H, I, J, K) stages. Graft of cells expressing Dkk1 at shield stage is unable to rescue the headless phenotype (panel H and arrowhead in panel K) induced by gsc/foxA3 knock-down, whereas it results in a loss of ventral mesoderm (arrowhead in panel J) showing that Dkk1 secreted from grafted cells was able to efficiently inhibit wnt8a activity even at long distance. (L) Frequency of phenotypic classes obtained at 24 hpf after the abovementioned transplant experiments. (B–E) Dorsal views at the 2–3 somite stage, (F–K) lateral views at 24 hpf.