Survey of the morphogenetic dynamics of the ventricular surface of the developing mouse neocortex

To understand the morphogenetic dynamics of the inner surface of the embryonic pallial (neocortical) wall, we immunohistochemically surveyed the cellular endfeet facing the lateral ventricle and found that the average endfoot area was minimal at embryonic day (E)12 in mice. This endfoot narrowing at E12 may represent a change in the mode of cell production at the surface from a purely proliferative mode that retains all daughter cells to a more differentiation-directed mode that allows some daughter cells to leave the surface. The apices of cells undergoing mitosis were 1.5-3.9 times larger than the overall cell apices and 6.7-8.7 times smaller than the cross-sectional area of mitotic somata. En face time-lapse monitoring of each endfoot permitted observation of its cell cycle-dependent size changes, division, and relationships with neighboring endfeet. Planar divisions oriented along the lateral-medial axis were less abundant than those oriented along the rostral-caudal axis at E10 and E11, but basal body distribution in each endfoot was random.