Early histogenesis of the teleostean retina: studies using a novel immunochemical marker, proliferating cell nuclear antigen (PCNA/cyclin).

Immunoreactive proliferating cell nuclear antigen or cyclin (ir-PCNA), detected by immunofluorescence using a human autoantibody, was used as a marker for proliferating neuroblasts during early development of the teleostean retina. In a killifish (Medaka) and a cyprinid (goldfish), ir-PCNA was present in all retinal cells at the monolayer stage (embryonic day 2 in Medaka, days 3-4 in goldfish). Subsequently ir-PCNA was lost, as neuroblasts became postmitotic in a centre-to-periphery and proximal-to-distal (ganglion cells first, photoreceptors last) sequence. In late larvae and adults, neuronal ir-PCNA was confined to the ring of proliferating neuroblasts at the retinal margin and scattered rod precursors in the outer nuclear layer. The changes in localization of ir-PCNA during development parallel closely the changes in localization of [3H]thymidine incorporation, reported previously.