Figure 3: Apical and basal processes on oRG cells and oRG apical daughters.

(a) oRG cell with apical process in GW18 human fetal oSVZ, identified by morphology after 18-h Adeno-GFP infection followed by fixation and Sox2 staining. Scale bar, 20 μm. (b) z-plane analysis of cell in panel a rotated 90° confirms the presence of apical process. Scale bar, 10 μm. (c) oRG cell lacking apical process in GW18 human fetal oSVZ, identified by morphology after Adeno-GFP infection and by Sox2 positivity. Scale bar, 20 μm. (d) z-plane analysis of cell in panel c rotated 90° confirms lack of apical process. Scale bar, 10 μm. (e) Time-lapse stills of a dividing oRG cell (blue arrowhead) in GW18 human fetal cortical slice labelled with Adeno-GFP. The oRG cell undergoes MST and produces an apical daughter (orange arrowhead) and a basal daughter (white arrowhead). The basal daughter retains the basal fibre and becomes a self-renewed oRG cell. The apical daughter produces an apical process immediately after MST (blue arrow), and a basal process several hours after MST (asterisk), adopting bipolar morphology. Scale bar, 10 μm. (f) Quantification of presence of apical process on all oRG cells in the GW16/18 human fetal i/oSVZ, and on apical daughters of oRG cell divisions after time-lapse imaging of GW16/18 human fetal cortex. All apical processes on apical daughters were produced within 1 h of MST. (g) Quantification of presence of basal process on apical daughters of oRG cell divisions after time-lapse imaging in GW16/18 human fetal cortex. Unlike the apical process, the basal process often takes more than 1 h to begin growing after MST.