Fig. 1. Visualisation of migrating neurons in Cdk5^+/+ and Cdk5^-/- mice by introduction of T1-EGFP plasmid into VZ cells by in utero electroporation. EGFP was introduced into (A) Cdk5^+/+ and (B) Cdk5^-/- mouse embryos at E14.5, and brains were fixed at E17.5. Sections were stained with anti-GFP antibody. Insets show areas indicated by arrows (a,b) at higher magnification. (A) Over the period of 3 days, neurons migrated into the CP with the typical bipolar shape (a) in Cdk5^+/+ mice. Migrating neurons in the CP extend their leading processes toward the pia and their axons (arrowhead) toward the VZ. In the SVZ-IZ, GFP-positive neurons of multipolar shape (b) are observed at this stage. (B) By contrast, in Cdk5^-/- mice neurons arrested in the SVZ-IZ in a multipolar shape (a), and their axons (arrowhead) run oblique within the SVZ-IZ. CP, cortical plate; SVZ, subventricular zone; IZ, intermediate zone; VZ, ventricular zone. Scale bar: 25 µm.