Figure 3

Spinal Non-apical Progenitors but Not Newborn Telencephalic Neurons Extend Basal Protrusions prior to Apical Detachment

(A) Image sequence showing a non-apical progenitor (NAP) with elongated basal protrusions (white arrows). The NAP retracts the apical attachment (blue asterisk in time point 4h20) before basal protrusions fully retract. Following apical detachment, the cell body rounds up away from apical surface of the neuroepithelium and undergoes mitosis (green arrow at time point 6h12). The NAP is neurogenically committed and produces two neuron daughters, each initiating axon growth at different time points (blue arrows indicate two growth cones at time 12h36) (Video S3). The apical surface is outlined by white dashed line. View is dorsal. All images are projected images from confocal z stacks.

(B) Graph showing the changes in length over time of the two basal protrusions from the NAP shown in A. Time points of when apical detachment, mitosis, and first axon elongation take place are indicated.

(C) Image sequence from time lapse showing a pair of differentiating telencephalic neurons. Long basal protrusions are not observed. Short basal protrusions from time point 0h35 on are the initial growth of axons. The neurons detach from the apical surface at 0h35 and 1h17 (blue asterisks). Extending axons are visible at 4h33 (blue arrows) (Video S4). Dashed lines show apical surfaces. Images are projections of confocal z stacks. View is dorsal.