True S-cones are concentrated in the ventral mouse retina and wired for color detection in the upper visual field

• Main Authors: Francisco M Nadal-Nicolás, Vincent P Kunze, John M Ball, Brian T Peng, Akshay Krishnan, Gaohui Zhou, Lijin Dong, Wei Li
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2020-05-01
• Series: eLife
• Subjects: genuine s-cone; cone distribution; cone cluster; mammalian photoreceptor; blue bipolar cells; color vision
• Online Access: https://elifesciences.org/articles/56840

Color, an important visual cue for survival, is encoded by comparing signals from photoreceptors with different spectral sensitivities. The mouse retina expresses a short wavelength-sensitive and a middle/long wavelength-sensitive opsin (S- and M-opsin), forming opposing, overlapping gradients along the dorsal-ventral axis. Here, we analyzed the distribution of all cone types across the entire retina for two commonly used mouse strains. We found, unexpectedly, that ‘true S-cones’ (S-opsin only) are highly concentrated (up to 30% of cones) in ventral retina. Moreover, S-cone bipolar cells (SCBCs) are also skewed towards ventral retina, with wiring patterns matching the distribution of true S-cones. In addition, true S-cones in the ventral retina form clusters, which may augment synaptic input to SCBCs. Such a unique true S-cone and SCBC connecting pattern forms a basis for mouse color vision, likely reflecting evolutionary adaptation to enhance color coding for the upper visual field suitable for mice’s habitat and behavior.