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Fig. 4
Neural crest and RB neuron development is Notch-dependent, but MTN and nTPC neurons do not require Notch signalling for their development. Embryos treated with 100 µM DAPT or DMSO from 30% epiboly were fixed at 24 hpf (A,B,E,F) or 19 hpf (C,D,G,H) and processed by in situ hybridisation with probes for isl1 (A,B,E,F) or crestin (C,D,G,H). In animals treated with DAPT, lateral aspects of the spinal cord reveal that there are many more RB neurons (arrows) relative to DMSO treated controls (A,B). Commensurate with this, there are less migrating neural crest cells (arrows) at spinal cord levels in DAPT-treated animals relative to controls (C,D). Dorsal views of the brain reveal that there are no obvious changes to nTPC (asterisk) or MTN (arrowheads) neurons in DAPT-treated embryos (E,F). However, lateral views of the head reveal that there are less migrating mesencephalic neural crest cells (arrows) in DAPT-treated animals relative to DMSO treated controls (G,H). Quantification of neurons revealed that DAPT treatment caused a significant reduction of RB neurons (**P<0.01), but no significant change (NS) to MTN or nTPC numbers. Scale bars = 100 µm (A–H).