SEEING IN UV - THE ROLE OF TYPE-4 CONES (‘TRUE S’) IN MOUSE VISION

Mice reconstruct visual scenes during daylight from activity patterns of type 1 (PR1; ‘M’;’M/S’;’green’) and type 4 (PR4; ‘true S’;’blue/UV’) cone photoreceptors (Jacobs et al., Nature, 1991; Baden et al., Plos. Biol., 2025). Despite evidence of behavioural relevance of PR4 for prey capture (Yoshimatsu et al., Neuron, 2020; Khan et al., Curr. Biol. 2023) and behavioral state in zebrafish (Fornetto et al., Cell, 2025), a precise role beyond colour vision in mice remains obscure.

We aim to address this gap with a combination of functional and behavioural methods in wild-type and transgenic PR4 knockout mice. Using a custom built recording and illumination setup we study how modulating the wavelength composition of ambient light influences the behavioural state of mice. On the functional side, we analyse the characteristics of glutamate responses in cone terminals of retinal explants during visual stimulation. The goal is to segregate PR4 and UV-sensitive PR1 cones and understand their distinct roles in visual processing and retinal circuit dynamics. Specifically considering their distinct connectivity patterns - PR4 exclusive connection to type 9 bipolar cells (Haverkamp et al., J. Neurosci., 2005; Nadal-Nicolás et al., eLife, 2020).

Currently we are conducting and analysing data for wild-type mice and once we record transgenic PR4 knockout mouse data we plan to compare them. We expect this research will contribute to scientific understanding of evolutionary roles of spectral channels and their conservation (or adaptation) in vertebrates.