Fig. 3. Pattern of expression of cdkis in the developing retina. A, bar chart showing times of expression of various cdkis with respect to time of generation of neuronal and glial cells. Note both Kip1 and Ink4d are expressed over similar periods but are progressively restricted to different cell types in the postnatal period. Kip2 has a bimodal pattern of expression first apparent with the generation of amacrine cells up until just before birth. Later, Kip2 reappears around postnatal day 3 where it is restricted to a discrete sublineage of amacrine cells. B, schematic diagram of the cellular development of the retina with respect to the cellular localization of the various cdkis. GCL, ganglion cell layer; INL, inner nuclear layer; ONL, outer nuclear layer. Information was adapted from data obtained by Dyer and Cepko (35) , Levine et al. (34) , and Dyer and Cepko (36) .4