Figure S3.

Videomicroscopy Analyses Demonstrating Abundant Direct Neurogenesis in the OB, but Not NCx, at E12.5, Related to Figure 2

(A) Individual frames from time-lapse videomicroscopy from OB (top) and NCx (bottom), imaged in brain slices 24hr after in utero electroporation of reporter plasmids at E12.5. Images from OB show one RGC (white arrowhead) dividing at t = 0 to generate one RGC (red arrowhead; Tbr1-, Tbr2-) and one neuron (green arrowhead; Tbr1+). Tbr1 and Tbr2 stain images are from a single confocal plane; dotted lines delimit the border of cells. Images from NCx show one RGC (white arrowhead) dividing at t = 3:30 hr to generate two more RGCs (solid green and red arrowheads), each inheriting an apical process and growing a basal process. These RGCs divide again at 18:30 and 20:30, respectively, to generate four RGCs (open green and red arrowheads; Tbr1-, Tbr2-). Scale bar: 15μm.

(B and C) Time plots from representative cell lineages starting as individual RGCs (B), analyzed by videomicroscopy as in (A), and frequency of cell division types observed (C). Three types of cells divisions produced direct neurogenesis (N from RG; red box), and the frequency of all three was much higher in OB than NCx. In contrast, indirect neurogenesis (N from IPC) was frequent in NCx but never observed in our OB imaging experiments. N = 44 divisions from 39 clones in NCx, 25 divisions from 25 clones in OB.

Scale bar: 10 μm.