Biology subjects

Louboutin, A.

Publications and source records attributed to Louboutin, A..

3 recordsLinked to original sources

bioRxiv2025

Increased sensitivity to myopia and altered retinal ON/OFF balance in a mouse model lacking Dusp4

Myopia, influenced by environmental and genetic factors, occurs when the emmetropization process fails to stop, causing excessive eyeball growth. Highly myopic animal models lacking a functional ON-pathway identified Dusp4 as a potential gene implicated in myopia. Here, we used a mouse model lacking DUSP4 to gain a better understanding of its retinal role and the mechanisms implicated in myopia development. Dusp4-/- mice have a reduced basal level of retinal dopamine and a higher susceptibility to lens-induced myopia. Dusp4 is expressed in ON-bipolar cells and a subset of OFF-bipolar cells in a light dependent manner. The absence of DUSP4 causes a hyperactivation of the MAPK/ERK pathway. Dusp4-/- mice showed reduced optomotor responses, increased ON-bipolar cell depolarization, reduced oscillatory potentials together with altered OFF and ON-OFF RGC responses to light flashes. These data provide insights into retina-driven mechanisms of myopization, nuancing the impact of ON and OFF pathways upon emmetropization.

neuroscience↗

bioRxiv2025

Accurate spatiotemporal retinal responses require a color intensity balance fine-tuned to natural conditions

Color vision is vital for animal survival, essential for foraging and predator detection. In mice, as in other mammals, color vision originates in the retina, where photoreceptor signals are processed by neural circuits. However, retinal responses to stimuli involving multiple colors are still not well understood. One possible explanation of this knowledge gap is that previous studies have not thoroughly examined how neuronal activity adapts to a 30 seconds to a few minutes timescale when exposed to multiple color sources. To address this, we systematically varied the UV-to-green light balance with a custom-built stimulator targeting mice opsins spectra while recording retinal ganglion cell responses across the dorso-ventral axis of the retina using multielectrode arrays. Responses to full-field chirp and checkerboard stimulations with alternating UV and green light revealed that more than one order of magnitude of intensity difference favoring green M-opsin over UV S-opsin is needed for a balanced reliability in retinal ganglion cell responses in the ventral retina. An incorrect balance, with slightly increased UV light, silenced responses to green illumination. To determine if these values are consistent with natural conditions, we analyzed isomerisation rates in the mouse retina across different times of the day. We found that the M- to S-opsin activation ratio remains constant through the mesopic-photopic range, and that our empirically determined values in the ventral retina align well with these natural conditions. These lie far from a simple equalization of M- and S-opsin isomerisation rates, which we found only balances ganglion cell responses in the dorsal retina. In conclusion, a finely tuned color intensity balance matching natural light spectrum is essential for accurately measuring both fast temporal responses and detailed spatial receptive fields in the ventral retina.

neuroscience↗

bioRxiv2024

Nonlinear spatial integration allows the retina to detect the sign of defocus in natural scenes

Eye growth is regulated by the visual input. Many studies suggest that the retina can detect if a visual image is focused in front or behind the back of the eye, and modulate eye growth to bring it back to focus. How can the retina distinguish between these two types of defocus? Here we simulated how eye optics transform natural images and recorded how the isolated retina responds to different types of simulated defocus. We found that some ganglion cell types could distinguish between an image focussed in front or behind the retina, by estimating spatial contrast. Aberrations in the eye optics made spatial contrast, but not luminance, a reliable cue to distinguish these two types of defocus. Our results suggest a mechanism for how the retina can estimate the sign of defocus and provide an explanation for several results aiming at mitigating strong myopia by slowing down eye growth.

neuroscience↗