Fig. 4. Impaired entry of interneuron progenitors into the OB in Arx-deficient mice. Nissl-stained parasagittal sections of wild-type (A,C,E) and Arx-deficient (B,D,F) mice at E12.5 (A,B), E16.5 (C,D), and P0 (E,F). At E16.5 and P0, the mutant mouse had a smaller olfactory bulb (OB) and shortened rostral migratory stream (RMS) (D,F). (G-J) In situ hybridization analysis of Dlx2 (G,H) and Dlx5 (I,J) expression in wild-type (G,I) and mutant (H,J) mice at P0. (K,L) Parasagittal sections of wild-type (K) and mutant (L) mice at P0 were labeled with anti-Arx antibody (red) and counterstained with PI (blue). In the Arx-deficient mouse (L), the antibody can recognize a truncated non-functional Arx protein. (M,N) Immunohistochemical labeling of GABA in wild-type (M) and mutant (N) mice at P0. While GABA is expressed in periglomerular cells in glomerular layer (GL) and granule cells in the granule cell layer (GCL) in the wild-type mouse (M), GABA-expressing cells are observed at the rostral end (arrowheads) and ventrally apposing region (asterisk) of the RMS (N). (O) Parasagittal section of P0 Arx heterozygous female brain was labeled with anti-LacZ antibody (red) and counterstained with DAPI (blue). Because Arx is located on the X chromosome, the Arx heterozygous female mouse is mosaic for Arx deficiency. LacZ(+) Arx-deficient cells failed to enter the OB. LGE, lateral ganglionic eminence; LV, lateral ventricle; MGE, medial ganglionic eminence; OE, olfactory epithelium. Scale bars: in F, 400 µm for A-F; in O, 400 µm for G-O.