Defining rod pathways for dim light vision in a simplex retina
By: David Umbertus
Department: Cellular & Molecular Biology
Faculty Advisor: Dr. Ivan Anastassov
The retina is a thin layer of tissue that lines the back of the eye and allows organisms to visualize the world around them. Most retinas have a duplex system of light sensitive cells, known as rod and cone photoreceptors. Cones are used for photopic vision (daylight/color) and rods are used for scotopic vision (dim light). There are three distinct rod pathways utilized in the mammalian retina; Primary, Secondary, and Tertiary. These pathways vary in sensitivity to light (from most to least sensitive) and usually utilize some part of the cone circuitry. However, L. erinacea (Little skate), is an organism with a pure-rod system, which can nonetheless perform in both dim and bright light conditions. In our research, we aim to understand how this organism transmits information from the input of rods and downstream to retinal ganglion cells without the ability to piggy-back onto cone circuitry. We will achieve this by looking at retinal anatomy using 3D-EM data and immunostaining for markers of cells that play a role in the different rod pathways. We will also perform RNA-Sequencing to determine the presence of common rod or cone genes typically found in duplex systems. I hypothesize that rod bipolar cells (the interneurons that typically connect to rods) will have a hybrid morphology, which allows for connections directly from rods to the output of the retina: ganglion cells. I also expect there to be expression of rod and cone genes that selectively mediate dim and bright light vision, respectively. Knowledge from our work could potentially be applied to diseased retinas and restore some visual function in humans by expanding the functional repertoire of the surviving healthy cells.