Fig. 6. Abnormal distribution of mitral cells and their dendrites in Arx-deficient mice. (A-F) Immunohistochemical analysis of Tbx21 expression in the olfactory bulb (OB) parasagittal sections (A-D) and coronal sections (E,F). In Arx-deficient mice at E16.5 (B) and P0 (D,F), mitral cells were found widely scattered in the OB, compared to wild-type (A,C,E). In a coronal section of the mutant OB (F), the mitral cell layer (MCL) showed an irregular contour: the MCL in the medial side of the OB (the right side in F) was thicker than in the lateral side (the left side in F). (G,H) Immunohistochemical analysis of L1 expression in the lateral olfactory tract (LOT) in coronal sections of P0 wild-type (G) and mutant (H) mice. LOT formation was normal in both mice. (I-P) Immunohistochemical analysis of Thy-1 (blue: whole dendrites of mitral cells) (I,J,O,P), reelin (red: proximal dendrites of mitral cells) (K,L,O,P), and Tbx21 (green: somata of mitral cells) (M,N,O,P) expression. In wild-type mice, mitral cell dendrites labeled with Thy-1 and reelin extended in a radial direction (I,K, arrowheads in O). In mutant mice, the orientation of proximal dendrites was variable (L, arrowheads in P), but the distal dendrites tend to reach the apical region of the OB (J,P). Thy-1 immunoreactivity in proximal dendrites in mutant mice disappeared (J,P). EPL, external plexiform layer; GL, glomerular layer. Scale bars: in F, 200 µm for A-F; in H, 100 µm for G,H; in P, 50 µm for I-P.