Fig. 6. Olfactory progenitors are specified to form neurons by HH10; placodal morphology is recapitulated in culture from HH13-14. (A-A'') Dlx3 (red) and Pax6 (green) are robustly expressed in HH8 explants; 1/3 cells co-express both (arrows, A'', yellow); non-overlapping Dlx3 (A,A'', arrowhead) or Pax6 (A',A'', arrowhead) domains appear distinct. (B) HH10 explant with neuronal differentiation; most neurons are Dlx3+/Hu+ (arrow), though some are Dlx3- (arrowhead). Insets show high-magnification views. (C) In HH10 explants, most cells are Pax6+ and few are Hu+ neurons. (C') Arrow indicates cluster of Dlx3+/Pax6+ cells. Dlx3+ and Pax6+ cells segregate from double-positive cells. (D) Olfactory placode explanted at HH13 undergoes thickening in culture and has some Dlx3+/Hu+ (red/blue) cells (arrows, insets). Pax7 (blue, distinguishable from Hu by nuclear localization) delineates nasal mesenchyme underlying olfactory placode. (E) Newly thickened placodal ectoderm shows robust neuronal differentiation (Hu+, blue); some neurons are Pax6+ (green; arrowheads; insets). (F) Location of olfactory precursors at HH8, HH10 and HH14 based on fate maps.