Neurog1 and Neurod4 act redundantly during development of zebrafish early-born olfactory neurons. (A-D) Confocal projections of GFP from the Tg(8.4neurog1:GFP) transgene in the olfactory placode of wild-type (A), neurog1 mutant (B), neurod4 morphant (C) and neurog1/neurod4 double loss-of-function (D) embryos at 24 hpf. Abrogation of both Neurod4 and Neurog1 function leads to a severe deficit in the differentiation of early-born olfactory neurons. Placodes are oriented with anterior up. Scale bars: 10 μM. (E) Counts of early-born olfactory neurons per placode at 24 hpf in wild-type, neurog1 mutant, neurod4 morphant, neurog1/neurod4 double loss-of-function embryos and neurog1 mutant embryos in which Neurod4 has been mis-expressed. A minimum of twelve olfactory placode was analysed for each context. Error bars represent s.d. *P<0.05, **P<0.001, ***P<0.0005, determined by t-test.