Similar results were obtained using Cux1 antibody as marker of the upper layers ( Figures 3H, 3L, and 3P). The nuclear marker FoxP1 is present in two stripes corresponding to layers III and V ( Figure 3F). Cell density is strongly reduced in NesCre/+;mInscfl/fl mice ( Figure 3J) while the number of cells in these layers is significantly increased in NesCre/+;R26ki/ki mice ( Figure 3N). Finally, layer

VI of the adult cortex, which is the first to be formed during embryogenesis, is also affected in both mutant conditions, as shown by immunostaining with the Foxp2 antibody ( Figures 3G, 3K, and 3O). A quantitative analysis of the cells positive for the various layer-specific markers ( Figure 3Q) confirms this phenotypic analysis. Screening Library These data demonstrate that mInsc levels are important for neurogenesis learn more and suggest that vertical orientation of the mitotic spindle is relevant for cortical development. To determine the developmental origin of those cortical phenotypes, we analyzed cortical development in mInsc knockout and overexpression mice (Figure 4). E11.5 brain sections from control, conditional knockout, germline-transmitted knockout,

and conditional knockin show no difference in the expression of nestin, Tbr1 (neurons), or Tbr2 (intermediate progenitors) (Figure S4), indicating that mInsc has no obvious role in early neurogenesis. We then stained coronal sections of E14.5 control and mutant brains with cresyl violet ( Figures 4A–4J).

We examined comparable sections at anterior and medial levels. No major structural abnormalities Metalloexopeptidase were detected at this stage, but NesCre/+;mInscfl/fl brains were smaller than controls ( Figures 4A and 4B). The lateral ventricles were enlarged, and overall cortical thickness as well as the protrusion of the lateral ganglionic eminence into the ventricles were reduced ( Figures 4A, 4B, 4E, and 4F). NesCre/+;R26ki/ki brains, on the other hand, exhibited increased cortical thickness ( Figure 4A, 4C, 4E, and 4G). These alterations in cortical thickness were observed in both central and lateral regions (refer to the scheme in Figure 4K). Quantification of those phenotypes showed that cortical thickness was reduced by around 20% both medially and laterally in NesCre/+;mInscfl/fl mice, while it was increased by about 20% in the medial region and by around 40% in the central and lateral regions in NesCre/+;R26ki/ki mice ( Figure 4L). A more detailed examination of these phenotypes revealed that the alterations in cortical thickness are largely due to changes in the IZ and the CP while the VZ is almost unaffected ( Figures 4H–4J). In NesCre/+;mInscfl/fl mice the thickness of the IZ and CP were reduced by about 25% and 40% ( Figure 4M) while in NesCre/+;R26ki/ki mice, both layers were thicker, up to more than three times ( Figure 4M).