Figure 9

Neurog1^−/−and Neurog1/2^−/−olfactory sensory neurons express neurotrophic receptors and ligands but fail to innervate olfactory bulb. (A) to (H) Expression of GAP43 (red, A to D) and OMP (green, E to H) with DAPI counterstain (blue, A to H) in embryonic day (E) 18.5 wild-type (A,E), Neurog1^−/− (B,F), Neurog2^KI/KI (C,G) and Neurog1/2^−/− (D,H) OBs/OEs. White arrows denote loss of synaptogenesis between the OE and the OB in Neurog1^−/− and Neurog1/2^−/− (B,D,F,H) olfactory systems, and arrowheads point to the accumulation of OSN axons in a FCM. (I) to (T) Expression of Ntrk1 (I) to (L), Ntrk2 (M) to (P) and Ntrk3 (Q) to (T) in E18.5 wild-type (I,M,Q), Neurog1^−/− (J,N,R), Neurog2^KI/KI (K,O,S) and Neurog1/2^−/− (L,P,T) embryos. (U) to (F') Expression of BDNF (U) to (X), NGF (Y) to (B'), NT3 (C') to (F'), in E18.5 wild-type (U,Y,C'), Neurog1^−/− (V,Z,D'), Neurog2^KI/KI (W,A',E') and Neurog1/2^−/− (X,B',F') embryos. Black arrows (J,L,N,P,R,T,V,X,Z,B',D',F') indicate loss of marker expression in outer layers of Neurog1^−/− and Neurog1/2^−/− OBs. Arrowheads (J,L,R,T,V,X,Z,B',D',F') point to FCM formation in Neurog1^−/− and Neurog1/2^−/− embryos. FCM, fibrocellular mass; OB, olfactory bulb; OBLS, olfactory bulb-like structure; OE, olfactory epithelium; ONL, olfactory nerve layer. Scale bars: 500 μm (A) to (Z), (A') to (F').