Caspase-dependent apoptosis of ON bipolar cells in the goldfish marginal retina

Progenitor cells proliferate at the retinal margin of adult goldfish, so that the developmental stages of maturing retinal cells are arranged in temporal sequence along the periphero-central axis. We studied the caspase-dependent apoptosis of ON bipolar cells, which were labeled by an antibody to protein kinase C (PKC). In both primary and secondary growth zones of the marginal retina, PKC+ cell somata were of two distinct sizes, large and small. A caspase inhibitor (zVAD-fmk), injected into the vitreous, increased the number of both large and small PKC+ somata (times approximately 2 and 1.1, respectively) in both growth zones. These data show that about one-third of immature ON bipolar cells were removed by caspase-dependent apoptosis before being incorporated into the mature retina.