Fig. 2. Neuron birth and asymmetric neuron production. (A) Schematic of neuron birth: green, -tubulin; red, cell membrane. I-III, migration of nuclei to apical surface 3 hours; IV-VII, mitosis 30 minutes; VIII-XI, apical-basal nuclei migration up to 9 hours post-mitosis; XII-XVI, release and retraction of the apical process, up to 15 hours and 25 hours post-mitosis, respectively; XVI-XVIII, cell body reorientation, production of an axon and return of sibling cell nucleus to apical surface for further division (times for five cells). (B) Asymmetric neuron production: a cell divides to produce a neuron (red dashed outline) and a progenitor cell (green dashed outline). Pink broken line indicates the cleavage plane. White broken line indicates apical surface. Blue broken line indicates basal surface. White box in final frame indicates region for comparison in C. Scale bar: 10 µm. Each image is a MIP through 30 z-sections imaged at 1.5 µm intervals. (B') Lineage tree for cells in B. (See Movie 2 in the supplementary material.) (C) Immunocytochemistry to confirm neuronal identity of the cell in B marked by a red dashed outline. Axonal process from eYFP-positive cell (green) in final stills frame (white box in B, and see Movie 2 in the supplementary material) labelled with 3A10 (red, a monoclonal antibody that recognizes a neurofilament-associated protein). MIP through 30 z-sections imaged at 1.5 µm intervals. Scale bar: 10 µm. (C'-C''') Region framed by dashed box in C. (C') eYFP; (C'') 3A10 labelling; (C''') eYFP/R merge. MIP through 3 µm of the field in view; scale bar: 5 µm.