HETEROGENEITY AMONG NEUROEPITHELIAL CELLS IN THE CHICK RETINA REVEALED BY IMMUNOSTAINING WITH MONOCLONAL-ANTIBODY PM1

Neuroepithelial cells appear as a homogeneous population of cells in t he cell cycle that seem to behave as pluripotent neural precursors. Th e study of the intrinsic heterogeneity and subtle developmental change s among neuroepithelial cells has been hindered by the tack of specifi c markers. To address that study, a panel of monoclonal antibodies was produced against early developing chick retina. The monoclonal antibo dy precursor marker 1 (PM1) labels most, if not all, of the early neur oepithelial cells in embryonic day 4 retinal sections. This pattern is transient since the labelling becomes restricted to the peripheral re tina as development proceeds and eventually disappears from the neuroe pithelial cells. However, apparently in parallel, the differentiating retinal ganglion cells become PM1-positive. The expression of the PM1 antigen, a 73x10(3) M(r) protein, as shown by western blotting, also d ecreases with development. In addition, a chick retina dissociated-cel l culture system, where retinal neuroepithelial cells actively prolife rate and undergo differentiation under defined conditions, in combinat ion with monoclonal antibody PM1, allowed us to characterize and quant ify the proliferating and differentiating neuroepithelial cells. Inter estingly, the fraction of total neuroepithelial cells that are stained with PM1 sharply decreases as retinal development proceeds, in correl ation with the staining pattern in sections from matched stages. These data thus reveal that the pluripotent neural precursors in the chick retina already represent an intrinsically heterogeneous population, an d that this population changes with development.