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Fig. 7
In neurog1 mutant zebrafish embryos, residual early-born olfactory neurons fail to express certain EON markers. (A-I) Confocal sections of in situ hybridisation and immunolabelling against robo2 and GFP from the Tg(8.4neurog1:GFP) transgene at 24 hpf in wild type (A-C), neurog1 mutant embryos (D-F) and neurog1 mutant embryos in which Neurod4 has been mis-expressed (G-I). Whereas early-born olfactory neurons in wild-type embryos robustly express robo2, expression is absent in neurog1 mutant embryos; mis-expression of Neurod4 partially rescues robo2 expression. (J-O) Confocal sections of in situ hybridisation and immunolabelling against robo2 and GFP from the Tg(8.4neurog1:GFP) transgene in wild-type (J-L) and neurog1 mutant (M-O) embryos at 36 hpf. The expression of robo2 never recovers in the few early-born olfactory neurons that develop in neurog1 mutant embryos. Scale bars: 10 μm.