Figure 1.

Progression of radial progenitor development in embryonic cerebral cortex. Initially, RGPs are established from an undifferentiated sheet of neuroepithelial cells (A). Radial glia then divide symmetrically and generate more radial glia (B). Subsequent asymmetric division of radial glial cells gives rise to daughter neurons and other radial glial cells (C and D). Neurons either somally translocate or attach to radial glial guides (C) as they migrate to the cortical plate. Asymmetric divisions of a radial glial cell can also yield a daughter neuron and an IP (D). IPs divide and generate neurons. During late stages of corticogenesis, as neurogenesis and migration dwindle, radial progenitors give rise to astrocytes or become ependymal cells (E). These distinct phases of progenitor development can be studied using clonal analysis of isolated progenitors, neurosphere assays, real-time tracking of labeled progenitors in embryonic cortex, or in utero imaging. An important point to note is that significant molecular and morphological heterogeneity of radial progenitors exists within the VZ of the developing cerebral cortex and is not outlined in this figure.