Fig. 4. FGF8-bead represses pax6.1 expression in the anterior neural plate. (A) FGF8-soaked unilaterally implanted beads repress pax6.1 expression in the posterior diencephalon of a wild-type embryo (arrowhead). An ectopic induction of eng3 expression was observed around the bead (B). In the noi mutant embryos, pax6.1 is also repressed by FGF8 (C) and eng3 is ectopically activated in the absence of functional Pax2.1 protein. In the noi mutant embryos pax2.2, a pax2.1-independent marker at the MHB, is not induced in the same timeframe (E,F). All pictures show dorsal views with anterior to the left, (B-D) show darkfield pictures of embryos in (A,C,D); stages as indicated; arrowheads indicate the posterior border of the expression domain of pax6.1 in the forebrain, circles indicate the position of the bead. DMB, diencephalic-mesencephalic boundary; eye, eye anlage; fb, forebrain; hb, hindbrain.