Purpose. We have previously identified arrays of early- differentiating cones in the fetal monkey retina using antibodies that recognize either the long and middle wavelength (L/M) opsin, synaptic vesicle protein, or an epitope specific to photoreceptor membranes (Wikler and Rakic, 1991, Nature, 351, 397-400; Wikler and Rakic, 1994, PNAS, 91, 6534-6538). To further characterize the opsin phenotype of these cones we have used PCR amplification to detect mRNAs for the L/M and short (S) wavelength- sensitive opsins in the fetal monkey retina. Methods. Retinae were taken from hesus monkeys sacrificed at embryonic (E) day E50, E70, E72, E80, or E90. Retinae were prepared as retinal wholemounts and divided into regions containing either the fovea and optic disc, parafoveal eccentricities, or peripheral margins of the retina. Tissue samples were immediately frozen and subsequently processed for PCR amplification of either L/MWS or SWS opsin-specific sequences. Results. No opsin expression was evident in any region of the E50 retina. By E70 and E72, however, mRNAs for the I/MWS and SWS opsins were detected in foveal regions of the retina, but only the SWS mRNA was detected in parafoveal and peripheral regions. By E90, both opsin mRNAs were evident at foveal and parafoveal eccentricities, however, only the SWS opsin mRNA was detected in the peripheral retina of this specimen. These data indicate that SWS opsin expression precedes the expression of the L/MWS opsin by approximately three weeks. Conclusions. The detection of SWS opsin mRNAs in peripheral monkey retina by E70 suggests that SWS cones express their photopigment within one week of their final mitotic division. In addition, these results suggest that periodically- positioned, early-differentiating cones in the fetal monkey retina may correspond to the SWS phenotype and that these arrays may serve as a template for the emergence of the adult mosaic of cone subtypes in the primate retina.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
All Science Journal Classification (ASJC) codes
- Sensory Systems
- Cellular and Molecular Neuroscience