Fig. 7

Knockout of Kif20a causes early cell cycle exit and precocious neuronal differentiation. a BrdU was given to pregnant mouse at E14.5 and embryonic brains were collected 24 h afterwards. R1, R2, and R3 indicated the BrdU-labeled cell ribbons located progressively from superficial regions to apical surface. BrdU⁺Ki67⁻ cells were progenitor cells that had left the cell cycle. More BrdU⁺Ki67⁻ cells in the total population of BrdU⁺ cells were present in the cortices of the Kif20a knockout-first embryos. Scale bar represents 100 μm. **P < 0.01. Error bars represent SD. b BrdU⁺Ki67⁻ cells that had migrated into the cortical plate in the Kif20a knockout-first cortex were positive for NeuN, indicating that these cells had become neurons. Arrows indicated examples of BrdU⁺Ki67⁻NeuN⁺ cells. Scale bar represents 100 μm. c In the upper panel, CAG-Cremyc-2A-GFP plasmid was introduced into the cortices of Ai9 (loxP-STOP-loxP-tdTomato) reporter mice at E13.5 by IUE. Electroporated brains were harvested at E15.5 for analysis. Majority of Cre-expressing cells (GFP⁺ cells) were positive for tdTomato expression, suggesting that Cre-mediated recombination was successfully carried out in these cells. In the lower panel, CAG-Cremyc-2A-GFP or control GFP plasmids were introduced into the cortices of Kif20a^fl/fl conditional knockout mice by IUE at E13.5 and the brains were analyzed at E16.5. Distributions of transfected cells in different radial regions of the cortex were scored. Scale bar represents 100 μm. The symbol ** (in green and blue font) indicates P < 0.01 with respect to the CP and VZ/SVZ distributions comparing to control GFP. Error bars represent SD. CP: cortical plate, IZ: intermediate zone, VZ/SVZ: ventricular/subventricular zone. Scale bar represents 100 μm