MOLECULES SPECIFIC TO PIGMENT EPITHELIAL-CELLS - EXPRESSION DURING INSITU DEVELOPMENT AND INVITRO LENS TRANSDIFFERENTIATION OF CHICK-EMBRYO PIGMENT-EPITHELIUM

The retinal pigment epithelium (PE) is a monolayer of cells and plays a vital role in the regulation of the neural retina. We prepared monoclonal antibodies directed against retinal PE cells to analyze the specificity and differentiation of these cells. Spleen cells from BALB/c mice immunized with chick embryo retinal PE cells were fused with myeloma cells. Seven independent monoclonal antibodies were obtained which specifically recognized PE cells but did not react with any other tissues examined. None of the monoclonal antibodies reacted with the choroid and skin of pigmented chicks, suggesting that these antigens were unrelated to melanogenesis. Two of the 7 antibodies reacted with the PE cells in the retina, ciliary body and iris; the remaining 5 antibodies were specific to the PE cells in the retina. In the process of in vitro lens transdifferentiation from PE cells, the distribution of an antigen detected by one monoclonal antibody changed from the cytoplasmic granules to the actin fibers and then its immunoreactivity declined. The other monoclonal antibodies did not react with the dedifferentiated PE cells and transdifferentiated lens cells, suggesting that the antibodies might be specific to the PE cells in the differentiated state, both in vivo and in vitro. During the in situ developmental process, each monoclonal antibody began to be immunoreactive to future PE cells in the optic eye cup at various stages from 72 to 120 h. The molecules common to all types of PE cells were expressed earlier than those specific to PE cells of the retina. Future ciliary and iridial PE cells appeared to transiently express the molecules specific to the retinal PE cells before the tip of eye cup contacted the lens vesicle. These data suggest that the monoclonal antibodies established in this study are powerful probes for exploring the functions and differentiation of PE cells.