Fig. 5

Loss of both Fgf3 and Fgf8 is needed to inhibit all placodal sox3 expression. (A–F) Wild type or ace/fgf8 mutant embryos were analysed by double in situ hybridization at 12 hpf for sox3 (red) and pax2a (blue) expression with or without injection of a morpholino targeting expression of Fgf3 (or its mismatch control). Right hand of each panel shows enlarged view of left side placode. Injection of either wild type or ace mutants with the fgf3 mismatch control had no effect on either sox3 or pax2a expression (C, D). Injection of wild type embryos with the fgf3 morpholino resulted in a reduced domain of expression of both pax2a and sox3 expression (E) as compared to untreated wild type embryos (A). The ace mutant embryos did not appear to differ from wild type embryos in their sox3 or pax2a expression (B). However, when ace mutant embryos were injected with the fgf3 morpholino, complete loss of sox3 and pax2a expression was seen (F). (G–L) In situ for either pax2a (G–I) or sox3 (J–L) expression in wild type embryos injected with morpholinos that targeted either fgf3 (G,J), fgf8 (H,K) or both fgf3 and fgf8 together (I, L). As seen with injection of ace mutants with the fgf3 morpholino (F), only loss of both fgfs resulted in complete loss of pax2a or sox3 expression in the prospective placodes (I, L).