Figure 5: MST and establishment of a horizontal spindle orientation are cell-intrinsic processes.

(a) Quantification of cleavage angles in oRG-like cells in dissociated culture in which transmitted light microscopy allowed visualization of spindle orientation. (b) Box plot of MST distances for oRG-like divisions in dissociated culture. (c) Time-lapse stills of dissociated, Adeno-GFP-labelled GW16 human neocortical progenitor cell divisions. oRG-like cell (white arrowhead) with basal process (red arrows) undergoes MST along the basal process and divides at 4:35 to produce two daughter cells: a ‘basal’ daughter (blue arrowhead) and an ‘apical’ daughter (yellow arrowhead). The apical daughter grows a basal fibre (red arrows) in the opposite direction as the original basal fibre, and subsequently undergoes MST in the direction of the newly generated fibre at 25:00 to produce two daughter cells (open yellow arrowhead, open red arrowhead). The basal daughter of the first division extends its basal fibre (red arrows) in the same orientation as the original basal fibre, and undergoes MST in the direction of this fibre. This cell divides at 28:45 to produce two daughter cells (open white arrowhead, open blue arrowhead). Scale bar, 20 μm.