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Francisco M. Nadal-Nicolas, Brian Peng, Akshay Krisnan, John Ball, Wei Li; Look up for color–‘true’ S-cones are concentrated in ventral portion of the mouse retina. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1103.
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Color, an important visual cue for survival, is encoded by comparing signals carried by cone photoreceptors with different spectral preferences. The mouse retina expresses two types of opsins, a short wavelength sensitive one (S-opsin, peak 360nm) and a long wavelength sensitive one (M-opsin, 508nm). The expression patterns of these two opsins form opposing gradients along the dorsal-ventral axis rendering the majority of cones to express both opsins. This unusual opsin expression pattern poses a challenge for color-coding, particularly with the large population of M+S+cones that lost narrow spectral tuning. However, it was discovered that a small population of cones preserved short wavelength spectral tuning by not expressing M-opsin (S+M- cones). These ‘true’ S-cones are thought to be evenly distributed across the retina and are critical for encoding color, especially in the dorsal retina where they are quasi-evenly distributed in a sea of ‘true’ M-cones (M+S-), a pattern akin to generic mammalian retinas. However, the distribution of true S-cones across the entire retina has not been thoroughly examined. We aim to quantify and assess the spatial distribution of the mixed, true S- and true M-cone in both mouse strains
Using pigmented (C57BL6) and albino (CD1) mouse strains, cone were doubly immuno-detected with antibodies for S and M opsins. We developed a highly reliable algorithm (R2=99-96%) to automatically quantify different cone types (All, S+, M+, true S; true M, and mixed cone)
Analysis of the distribution of different cone types revealed that true S-cones are highly concentrated in ventral retina in both strains. Despite the vast difference in S-opsin expression pattern, the distribution of true S-cones is strikingly similar between the pigmented and albino mice. In addition, we found that true S-cones in the ventral retina are not evenly distributed but form clusters. Thus, enriched true S-cones in the ventral retina may provide an anatomical basis for mouse color vision
The true S-cone pattern likely reflects evolutional adaption to enhance short-wavelength signaling and color coding for the upper visual field suited for mouse habitat and behavior. It is also remarkable that despite the different S-opsin expression pattern between the mice strains, the true S-cone population and distribution are strikingly similar, suggesting a common functional significance
This is a 2020 ARVO Annual Meeting abstract.
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