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Klaudia Szabo, Arnold Szabo, Anna Enzsoly, Pál Röhlich, Agoston Szel, Akos Lukats; Misplaced Photoreceptors in the Retina of Developing Rodents. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3941.
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© ARVO (1962-2015); The Authors (2016-present)
In the retina of the primarily nocturnal animals, such as rodents, rod photoreceptors are the dominant components in signal perception. Their photosensitive pigment -rhodopsin- can be detected with immunocytochemistry from birth. Previous studies showed, that besides the extensive staining of the photoreceptors, a less numerous population of cells was also labeled in the inner nuclear, and ganglion cell layers during postnatal development. The aim of the present study was to describe and compare the morphology, the number and the staining characteristics of this peculiar population in various rodent species.
Retinas of Spague-Dawley rats, Siberian hamster, Syrian golden hamster and mouse of different ages (P0-P21) were studied. Immuncytochemical labeling of different rhodopsin specific antibodies were used on whole mounted retinas and cryosections. Double labeling with several retinal cell type specific antibodies was used to further characterize the rhodopsin positive cell populations located in the inner nuclear and ganglion cell layers.
We observed rhodopsin expressing cells in the inner nuclear and ganglion cell layers of the retina in all four species studied. They comprised approximately 1% of all labeled cells, often appeared in smaller clusters and morphologically resembled bipolar, amacrine or ganglion cells. They could be reliably detected using several different sets of antibodies, raised against the C-, and the N-terminal of rhodopsin, respectively. These cells first appeared at the 4th postnatal day (P4), reached their maximum density at P14 and disappeared entirely by the end of the 3rd week. Double labeling could not confirm the presence of any other type of photopigment in their cytoplasm. Staining with different inner retinal cell type specific antibodies showed colocalization only in case of recoverin, that is known to label photoreceptors besides bipolar and amacrine cells.
Our results showed that approximately 1% of all rhodopsin expressing cells are not located amongst other photoreceptors during development, but are displaced to the inner retinal layers. Although they lose almost all morphological resemblance to photoreceptors, colabeling indicates that they are most probably misplaced rods that fail to integrate in the retinal mosaic.
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