Micrograph sections of d40 hCOs electroporated with GFP-empty vector control or GFP-CSTB and analyzed 5 dpe. Sections were then immunostained for GFP and KI67. The dashed lines represent the apical surface of the cavities/ventricles (V-like). The cortical plate like side is indicated (CP-like). Quantification of the total number of proliferating KI67+ cells/area (µm2) of V-like structures transfected with GFP-empty vector control or GFP-CSTB in (A). 