HOUSTON – (Nov. 27, 2018) – Working to protect vision and prevent blindness, researchers at The University of Texas Health Science Center at Houston (UTHealth) recently received more than $4 million in grants from the National Institutes of Health’s National Eye Institute to study the photoreceptors that convert light into brain signals.

“This research could lead to a better understanding of how the retina works and how we see during day and night. It may also reveal new therapeutic strategies to prevent or correct degenerative retinal disease,” said Christophe Ribelayga, PhD, associate professor of ophthalmology and visual science at McGovern Medical School at UTHealth.

Photoreceptors are responsible for color vision and night vision, and there are two types: rods and cones, according to the National Academy of Ophthalmology. Photoreceptor issues can contribute to color blindness, retinitis pigmentosa, and Usher syndrome.

“Researchers will use the mouse as a model system and focus on electrical synapses between photoreceptors,” Ribelayga said. “Although it is generally assumed that rods operate under dim light or at night, and cones under bright light or during the daytime, we have come to realize that this is not exactly true.”

Ribelayga said a wealth of evidence now indicates that rods and cones can interact through gap junctions, allowing the mixing of their electrical signals. Remarkably, the strength of these connections fluctuates with the time of day and consequently changes the way retinal circuits process visual signals.

“We have developed a variety of genetically modified mouse lines as well as new techniques to study this process,” Ribelayga said. “We will use these tools to identify the signaling pathways that support the daily plasticity of coupling between rods and cones. It is remarkable that this synapse has been ignored by the field for a long time and yet it is the first synapse of the visual system.”

Ribelayga and Stephen C. Massey, PhD, holder of the Elizabeth Morford Distinguished Chair in Ophthalmology and research director for the Ruiz Department of Ophthalmology and Visual Science, were awarded $2.7 million to study the function of rod/cone gap junctions in retinal circuitry (R01EY029408). In addition, they received an administrative supplement of nearly $300,000 (R01EY029408-S1) to help purchase a two-photon microscope for this work. 

Ribelayga and Jiaqian Wu, PhD, associate professor in the Vivian L. Smith Department of Neurosurgery and the UTHealth Center for Stem Cell and Regenerative Medicine, received $424,000 to examine the role of circadian clocks in photoreceptor cell development, maintenance, and function (R21EY028647).

John O’Brien, PhD, professor of ophthalmology and holder of the Louisa Stude Sarofim Distinguished Chair in Ophthalmology; Chai-An Mao, PhD, assistant professor of ophthalmology; and Ribelayga together received $424,000 to examine the role of electrical synaptic plasticity in retinal function using a mouse model (R21EY027965).

Vision scientists at UTHealth are also supported by a vision core grant from the National Eye Institute (P30 EY028102). The core grant is for $400,000 per year in direct costs over a five-year period.

Massey, O’Brien, Mao, Wu, and Ribelayga are on the faculty of The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences.