Figure 2.

Blocking Notch/Rbpj signaling in cranial neural crest‐derived cells from E3.5 results in neurogenesis on the olfactory nerve. Parasagittal sections of chicken embryos at E5.5 that had received grafts of midbrain and caudal forebrain neural folds from ex ovo‐electroporated donor embryos at E1.5, with doxycycline injection at E3.5. (a–a³) Control EGFP‐targeted embryo, showing ISH for Sox10 and immunostaining for EGFP and Tubb3 (neuronal class III beta‐tubulin). EGFP‐targeted cells are seen in the neural folds, frontonasal mass and on the olfactory nerve. (b–b³) Higher‐power view of boxed region in panels a–a³, showing the olfactory nerve near the forebrain. A few EGFP‐targeted cells on the olfactory nerve lack expression of the OEC marker Sox10 (arrows), but most are Sox10‐positive (arrowheads highlight examples). (c–c³) Immunostaining on a nearby section for the neuron‐specific marker Elavl3/4 shows that EGFP‐targeted neural crest‐derived cells on the olfactory nerve are Elavl3/4‐negative, i.e., are not neurons (arrowheads highlight examples). (d–d³) A DN‐Rbpj/EGFP‐targeted embryo (the same embryo shown in Figure 1c–c²), showing ISH for Sox10 and immunostaining for EGFP and Tubb3. DN‐Rbpj/EGFP‐targeted cells are seen in the frontonasal mass and along the olfactory nerve. (e–e³) Higher‐power view of boxed region in panels d‐d³, showing the olfactory nerve near the forebrain. A few DN‐Rbpj/EGFP‐targeted cells on the olfactory nerve express Sox10 (arrowheads highlight examples), but most are Sox10‐negative (arrows highlight examples). (f–f³) Immunostaining on a nearby section for the neuron‐specific marker Elavl3/4 shows that although some DN‐Rbpj/EGFP‐targeted neural crest‐derived cells on the olfactory nerve are not neurons (arrowheads), many are neurons (arrows highlight examples). E, embryonic day; fb, forebrain; oe, olfactory epithelium. Scale‐bars: 100 μm (a–a³, d–d³), 50 μm (b–c³, e–f³)