Abstract
Abstract: :
Purpose: Studies of cone development in several mammalian species (e.g., rats, gerbils) indicate a cell transdifferentiation pattern from S cones to M cones. In rabbits, however, it has been reported that S cones and M cones sequentially differentiate without photopigment coexpression (Szepessy et al., IOVS, 2000, 41:3171–3175). To determine the mechanism of cone cell development in the postnatal rabbit retina, we reexamined this phenomenon with the help of recent commercially available antibodies raised against S cone opsin and M cone opsin. Methods: Immunocytochemistry with anti–photopigment antibodies was used to identify the expression patterns of S cone opsin and M cone opsin in the wholemount retina of postnatal New Zealand White rabbits (P0–P10). Results: In contrast to the results reported in Szepessy et al., 2000, we found that both S cones and M cones can be detected as early as postnatal day 0, using commercial antibodies (Chemicon or Santa Cruz) but not OS–2 and COS–1 (generous gifts of Agoston Szel). Double labeling experiments revealed that there is a significant coexpression of S cone opsin and M cone opsin in the individual cone cells during early retinal development. Conclusions: With the increased sensitivity of commercially available anti–photopigment antibodies, our results showed that both S cone opsin and M cone opsin are expressed before birth in the rabbit retina. Furthermore, it appears that many M cones in the adult may derive from the cell transdifferentiation of S cones in the early development.
Keywords: photoreceptors • color pigments and opsins • visual development