EXPRESSION OF THE MAS PROTOONCOGENE IN THE RETINAL-PIGMENT EPITHELIUMOF THE RHESUS MACAQUE

The MAS proto-oncogene codes for a seven transmembrane protein which h as been previously localized to specific regions of the hippocampus an d cerebral cortex in the rat central nervous system. Because MAS has b iological properties related to the growth and differentiation of cell s of neuroectodermal origin, we investigated the distribution of MAS e xpression in the rhesus macaque retina by in situ hybridization. A 330 base pair (bp) segment of the human MAS sequence was subcloned and us ed to generate single-stranded cRNA probes for these studies. Our resu lts demonstrated little, if any, positive signal over the neurons of t he retina. The use of epi-polarization microscopy, however, revealed a distinct positive labelling of retinal pigment epithelial (RPE) cells . These studies suggest the use of MAS as a possible marker for the re tinal pigment epithelium.