Cortical interneuron migration defects of Foxc1hith/hith fetuses. (A-F) Coronal hemi-sections through the X-gal stained forebrains of wild-type (WT) (A-C) and Foxc1hith/hith (D-F) fetuses expressing the Dlx5/6-lacZ transgene at E16.5. From left to right, three, progressively more posterior levels through the forebrain are shown. Red asterisks in (D-F) indicate the disruption of interneuron migration in the mutant marginal zone (MZ). The close-ups in (C', F') show the increased width of the deep migratory stream, at the intersection of the subventricular zone with the intemediate zone (SVZ/IZ), in the dorsal cortex of the mutant. (G) The results of the quantitative analysis of Dlx5/6+ migrating interneurons for the SVZ/IZ and MZ, respectively. Error bars indicate average deviation. The cell counts were conducted on a 500 μm long cortical segment of the dorsal cortex comparable to the close ups in (C', F'). In the mutant the number of labeled cells is significantly decreased in both migratory streams (SVZ/IZ, P = 0.019; MZ, P = 0.024). Asterisks indicate statistical significance. Scale bars: 500 μm (A-F); 100 μm (C', F'). CP, cortical plate; Cx, cerebral cortex; HT, hypothalamus; IZ, intermediate zone; LGE, lateral ganglionic eminence; LV, lateral ventricle; Me, meninges; MZ, marginal zone; Se, septum; SVZ, subventricular zone; Th, thalamus.