TRANSDIFFERENTIATION OF ADULT HUMAN PIGMENT-EPITHELIUM INTO RETINAL CELLS BY TRANSFECTION WITH AN ACTIVATED H-RAS PROTOONCOGENE

The identification of homologs to viral oncogenes in normal cells coupled with development of techniques for DNA transfer into cells offers a powerful approach to dissect the processes associated with differentiation-specific oncogenes. We have derived cell lines by transfection of viral DNAs and proto-oncogenes into primary retinal pigment epithelial (RPE) cells. Establishment of cell lines was successfully achieved with the SV40 large T-antigen gene activated form of Harvey (H)-ras proto-oncogene, c-myc, and adenovirus E1A. The cell lines derived using the H-ras oncogene appeared to contain cells with a neuronal phenotype. This feature was not observed in cell lines established with the other oncogenes. Characteristically, H-ras-transfected cells all exhibited features associated with neurons around 10-14 passages. The transdifferentiated cells were biochemically characterized and found to express neuronal markers, such as neurofilament protein and neuron-specific enolases. The specific neuronal changes were restricted to only two primary cultures of RPE derived from carcinoma donors. Although transdifferentiation of pigmented cells of iris, or the retina, into the lens has been demonstrated, our studies presented in this report provide evidence that RPE cells from adults can transdifferentiate into neurons under the influence of a specific oncogene. To the best of our knowledge, this is the first report on transdifferentiation of adult human pigment epithelium into a neuronal cell type.