Localization of protein kinase C to UV-sensitive photoreceptors in the mouse retina

The present study has identified a population of cone photoreceptors in the murine retina that are uniquely immunoreactive for protein kinase C (PKC). Wavelength-sensitive cone subtypes are segregated along the dorso-ventral axis in the mouse retina with ventral retina occupied exclusively by ultraviolet wavelength-sensitive (UVWS) cones, and dorsal retina dominated by middle wavelength-sensitive cones. PKC-positive cones are found primarily in the ventral retina, and double-label immunocytochemistry using a short wavelength-sensitive opsin antibody confirms that they specifically correspond to the UVWS cone subtype. The PKC antibody, as documented in other mammals, also identifies rod bipolar cells in the mouse retina. UVWS cones and bipolar cells have previously been shown to share transcriptional regulatory elements, as observed in transgenic mice encoding a portion of the human SWS-opsin promoter controlling the lacZ reporter gene. In such mice, the transgene product, beta-galactosidase, is expressed in populations of both cones and bipolar cells. The present study confirms that lacZ-expressing photoreceptors are indeed PKC-positive photoreceptors, but that the lacZ-expressing bipolar cells are not the PKC-positive rod bipolar cells. These cells must correspond to a type of cone bipolar cell.