Micrograph sections of d40 hCOs electroporated with GFP-CSTB expressing vector or GFP-R68X mutant and analyzed 5 dpe. Sections were 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)(F) and Ki67+GFP+ cells/area(µm2)(G) of ventricles like structures transfected with GFP-empty vector control, GFP-CSTB or GFP-R68X mutant in (E). 