Fig. 1. Experimental setup for time-lapse video recording. (A) Retinal explants from newborn rats were cultured on organotypic filters, which allow the culture medium to diffuse through the explant by capillary action. The edge of the explant was folded over, which allowed RNECs infected with a GFP-encoding retrovirus to be observed along their apico-basal axis. Areas of the folded edge are shown after (B) 3 hours and (C) 6 days. Note that all mitotic cells are at the apical surface of the neuroepithelium in B and that two, distinct cell layers have developed in C, just as observed in vivo. However, the retinal ganglion cells die in the explant because they lack neurotrophic support from their normal target cells. Scale bar: 20 µm.