Fig. 9. A schematic representation of OB structures in wild-type and Arx-deficient mice at P0. Diagrams show horizontal sections of the olfactory bulb (OB) in wild-type (A) and Arx-deficient mice (B). Anterior is to the top and lateral is to the left. Mutant mice showed the impaired entry of interneuron progenitors (orange) into the OB, the loss of TH(+) periglomerular cells (dark pink), and the disorganization of OB layer structure. The innervation of olfactory axons (purple) and the apical projection of radial glial fibers (blue) were observed only at the rostromedial side of OB in mutant mice. The olfactory axons that failed to reach mutant OB formed the fibrocellular mass (FCM) in front of the OB. RMS, rostral migratory stream.