Biology subjects

Ball, J. M.

Publications and source records attributed to Ball, J. M..

2 recordsLinked to original sources

bioRxiv2021

Cone mitochondria act as microlenses to enhance light delivery and confer Stiles-Crawford-like direction sensitivity

Evolution endeavors to maximize the function of biological structures in organisms, and the vertebrate eye is no exception. Cone photoreceptors in the retina are among the most energy-demanding cells in our body, necessitating numerous mitochondria. Intriguingly, these mitochondria adopt a peculiar spatial aggregation immediately beneath the cone outer segment (OS) that houses light-sensitive opsin molecules. Here we demonstrate, via direct live imaging and computational modeling of ground squirrel cones, that such mitochondria bundles concentrate light to enter the OS for detection. This "microlens"-like feature of cone mitochondria produces an angular dependence of light intensity quantitively consistent with the Stiles-Crawford effect, a psychophysical phenomenon believed to improve visual resolution. Thus, in addition to their function as a necessary powerhouse, cone mitochondria play a critical optical role.

neuroscience↗

bioRxiv2020

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

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 pattern forms a basis for mouse color vision, likely reflecting evolutionary adaption to enhance color coding for the upper visual field suitable for mices habitat and behavior.

evolutionary biology↗