RET-PE10: A 61 kD polypeptide epitope expressed late during vertebrate RPE maturation

Purpose. This study sought To learn more about the mechanisms that determine and maintain the differentiated state of the retinal pigment epithelium (RPE). Methods. Monoclonal antibodies were raised against human RPE and used in conjunction with other antibodies. Immunocytochemical and biochemical analyses were performed on tissue sections and cells in culture. Results. An RPE-specific epitope, RET-PE10, has been detected as a 61 kD cytoplasmic polypeptide in a variety of mammalian, amphibian, and avian species. In the rat, RET-PE10 was expressed late in eye development, with a faint initial labelling of the RPE in central regions at postnatal day 9 (PN9) that increased to adult levels and extent of staining by PN14. RET- PE10 expression initially was present in overnight cultures of dissociated rat RPE cells but was lost rapidly from these cultures during the first week. Comparison of the staining patterns of RET-PE10 with those of various cytoskeletal elements suggests that RET-PE10 may be associated with part of the intermediate filament network. Culture of whole eyecups also resulted in a loss of RET-PE10 expression. RET-PE10 expression was normal in eyes of adult rd rd mutant mice. Conclusions. RET-PE10 is a late-appearing market of RPE differentiation. The results also suggest that the maintained expression of RET-PE10 depends upon extrinsic factors but that these do not include maintained contact with Bruch's membrane or light-induced retinal activity.