Novel retinal pigment epithelial cell gene (Norpeg, Rai14), a developmentally regulated mouse gene, encodes a protein containing six ankyrin repeats and a coiled-coil domain. The objective of the present study was to characterize the Norpeg protein and to analyze its expression in mouse retina using an antibody preparation that we developed. The approximately 110kDa Norpeg was immunoprecipitated and characterized by mass spectrometry. Primary cultures of Müller and ganglion cells isolated from the mouse retina were found to express Norpeg when analyzed by immunoblotting and immunofluorescence microscopy. Immunofluorescence analysis of normal mouse retina sections demonstrated that Norpeg is expressed in cells of the ganglion cell layer, inner nuclear layer as well as in the retinal pigment epithelium. Immunoreactivity was also evident in the radial glial (Müller) cell fibers.