Fig. 8. Disorganization of OB layer structure in Arx-deficient mice. (A-H) Immunohistochemical analysis of NCAM (blue: olfactory axons) (A,B,G,H), Tbx21 (green: mitral cells) (C,D,G,H), and GABA (red: interneurons) (E,F,G,H) expression on horizontal sections of olfactory bulb (OB) from wild-type (A,C,E,G) and Arx-deicient (B,D,F,H) mice at P0. In the wild-type mouse, the olfactory nerve layer (ONL) surrounded the whole surface of the OB (A,G). In contrast, the ONL was present only in the rostromedial side (right side in B) of the OB and most of the olfactory axons terminated in the FCM (asterisks in B,H) in the mutant mouse. Besides the ONL, the formation of the mitral cell layer (MCL in C,G), glomerular layer (GL in E,G), and granule cell layer (GCL in E,G) was affected in mutant OB (D,F,H). (I,J) Magnified images of NCAM (red) and DAPI (blue) labeling on OB horizontal sections of P0 wild-type (I) and mutant (J) mice. Protoglomeruli structures (arrowheads in I) were only observed in wild-type OB. (K,L) Immunohistochemical analysis of NCAM (red: olfactory axons) and neuropeptide Y (NPY) (green: olfactory ensheathing glia in the inner ONL) expression on horizontal sections of P0 wild-type (K) and mutant (L) mice. NPY immunoreactivity was observed in the inner portion of the ONL in both wild-type and mutant OB. (M,N) Immunohistochemical analysis of NCAM (red: olfactory axons) and S100 (green: olfactory ensheathing glia in the outer ONL) expression in P0 wild-type (M) and mutant (N) mice. S100 immunoreactivity was observed in the outer portion of the ONL in both wild-type and mutant OB and in the FCM (asterisk in N) of mutant mouse. (O,P) Immunohistochemical analysis of NCAM (red: olfactory axons) and GLAST (green: radial glia) expression in P0 wild-type (O) and mutant (P) mice. GLAST(+) radial processes were observed throughout the OB of the wild-type mouse (arrowheads in O). In contrast, radial processes were only found in the rostromedial region of mutant OB (arrowheads in P) where the innervation of olfactory axons occurred. (Q-V) Immunohistochemical analysis of expression patterns of cell recognition molecules on horizontal sections of P0 wild-type (Q,S,U) and Arx-deficient (R,T,V) mice. (Q,R) NCAM (red) and OCAM (green). (S,T) NCAM (red) and neuropilin-1 (Npn-1) (green). (U,V) NCAM (red) and neuropilin-2 (Npn-2) (green). Arrowheads in (Q,S,U) indicate the OCAM(+)/Npn-1(–)/Npn-2(+) tongue-shaped area in the wild-type mouse (Nagao et al., 2000). Arrowheads in R,T,V indicate a subpopulation of olfactory axons reaching the OB in the mutant mouse. Asterisks in R,T,V: FCM. Scale bar: in V, 200 µm for A-H and K-V; 50 µm for I,J.