Fig. 8. Role of Xiro1 on isthmic organizer in vitro. Embryos were injected at one-cell stage with the mRNAs described, the animal caps were explanted and conjugated at stage 10 and cultured until the equivalent of stage 17. At this stage the gene expression was assayed. (A) Injection of 2 ng of Gbx2 mRNA do not induce Xiro1 expression (0%, n=36). (B) In caps injected with 5 ng of Otx2 mRNA, Xiro1 expression is induced (arrowheads, 65%, n=23; inset shows uninjected animal caps). (C) Caps injected with 2 ng Xiro1-EnR mRNA express Gbx2 (arrowheads, 57%, n=46; inset shows uninjected animal caps). (D) Otx2(5 ng)//Xiro1(2 ng) conjugates express En2 (arrowheads, 90%, n=30) in the Otx2 territory (arrow indicates the X-Gal stain in the Xiro1-expressing caps). (E) Fgf8 also is induced in these conjugates (arrowhead, 71%, n=34, arrow shows the X-Gal stain in the Xiro1 caps). (F) Interference with Xiro1 function with HD-GR-E1A (0.5 ng) at stage 12 suppressed En2 expression in the Otx2 expressing cap (40%, n=33).
