Figure 2

Retinoic acid signaling affects olfactory neural differentiation. (A,B) Endogenous RA activity, detected by the RARE-lacZ reporter transgene in E11.5 mouse OE, spatially segregated with differentiating (TuJ1-labeled) neurons. (C-E) Disulphiram bead administration to HH14 chick embryos leads to an absence of Pax6+ progenitors in most of the OP (D), whereas all-trans-RA (AT-RA) treatment leads to a basal location of Pax6+ cells (E). (C) Control embryo (DMSO soaked bead). Main panels: transverse sections; insets: whole-mount views. (F,G) Culture of HH14 chick OPs in medium devoid of vitamin A stimulates neurite outgrowth from differentiating (TuJ1+) ORNs. (H,I) A similar effect is seen in E10.5 mouse olfactory explants. Insets: explants labeled with Dlx6 (F,G) or Dlx5 (H,I) after culture, showing that the OE developed similarly in both conditions. (J-L) Culture of E10.5 mouse OE in presence of disulphiram strongly increases ORN neurite outgrowth (K), whereas AT-RA treatment has an inhibitory effect (L), in comparison to the control (DMSO-treated) explants (J). (M,N) Explants from E10.5 Raldh3^−/− embryos form differentiating and neurite-extending ORNs (TuJ1-labeled), whether cultured in absence (M) or presence (N) of vitamin A.