Fig. 4. Pattern of expression of the cdkis in the developing cerebral cortex. Bar chart showing times of expression of the various cdkis with respect to the time of generation of the cellular layers of the cerebral cortex. Two simple schematics outline the evolution of the various cortical layers (I -VI). Ink4c and Kip2 are only expressed during embryogenesis. Whereas Ink4c is localized to the VZ, Kip2 is predominant within the developing cortical plate (CP). In contrast, Cip1 is only expressed in the late postnatal period and adulthood within the olfactory bulb. Ink4a, Ink4d, and Kip1 are expressed throughout cortical development but are progressively restricted in late postnatal life to the olfactory bulb, anterior sub-VZ, cortex and ependyma, respectively. IZ, intermediate zone; MZ, marginal zone. Information was adapted from data obtained by Lee et al.(25) , Zindy et al. (42) , van Lookeren et al. (41) , and Coskun and Luskin (43) .