Table 1.

Cleavage plane orientation and distribution of apical membrane in mitotic mouse NE cells

Apical membrane distribution	Cleavage plane orientation
	Vertical	Oblique	Horizontal
	(90–60°)	(60–30°)	(30–0°)
Equal	76	1	0
Unequal	30	6	3
Data for various developmental stages (E9.5–14.5) and brain regions (forebrain, midbrain, hindbrain) were pooled because the vast majority of mitotic NE cells showed a vertical cleavage plane orientation for any of the developmental stages and brain regions analyzed (see below). For the equal versus unequal distribution of apical membrane in various developmental stages and brain regions, see Figure 6. Numbers of cells were: E9.5 forebrain, n=11; E10.5 forebrain, n=4; E11.5 forebrain, n=18; E14.5 forebrain, n=15; E9.5 midbrain, n=2; E10.5 midbrain, n=10; E11.5 midbrain, n=44; E9.5 hindbrain, n=1; E11.5 hindbrain, n=11. Note that even at advanced stages of neurogenesis in the forebrain (E14.5), only one of 15 mitotic NE cells showed a cleavage plane orientation that was not vertical.