Renna receives NIH grant to map neural pathways in the retina

Dr. Jordan Renna, professor and chair of the Department of Biology, and his student research team have received a three-year, $425,000 R15 Academic Research Enhancement Award from the National Eye Institute (NEI), part of the National Institutes of Health, to map neural pathways in the retina.

The retina is the light-sensitive tissue at the back of the eye, where visual information begins to be processed before being sent to the brain. Renna's laboratory studies how retinal circuits are wired using electron microscopy-based connectomics, which the journal Nature Methods named its 2025 Method of the Year. The approach uses large-scale, three-dimensional electron microscopy to trace individual neurons and their synaptic connections at nanometer resolution. At that level of detail, researchers can revisit familiar circuits and identify connections that were previously unknown or missed.

Looking beyond the classic pathways

For decades, models of retinal circuitry have centered on a well-established pathway in which visual signals travel from photoreceptors through bipolar cells and ultimately toward the brain, while interneurons refine those signals within specific layers of the retina.

Renna and his students are mapping two important classes of neurons that help shape this early visual processing: horizontal cells and dopamine-producing neurons. The researchers' work seeks to better understand how these cells regulate retinal circuitry and influence the visual information ultimately transmitted to the brain under different conditions.

UA students at the center of the research

Students are leading major parts of the project. Laurence Johnson, an integrated bioscience doctoral student, is mapping the connections made by horizontal cells, which help shape the earliest stages of visual processing. Kendall Farley, who is pursing master's degree in biology, is investigating the circuitry of dopamine-producing neurons and how they interact with the rest of the retinal network.

Farley's preliminary data helped shape one of the NIH grant's aims. She has since secured funding of her own: a $5,000 summer research grant from Prevent Blindness Ohio supported her reconstruction of a single dopamine-producing neuron. Under the NIH award, she will expand that work to reconstruct and analyze five or six cells.

The work also extends to undergraduate students through the Department of Biology's Tiered Mentoring model, which brings undergraduate and graduate students together on research teams. In November, seven members of the Renna Lab, including undergraduate and graduate researchers participating in Tiered Mentoring, will travel to Washington, D.C., for the Society for Neuroscience annual meeting. There, they will present findings from this work at one of the world's largest gatherings of neuroscientists.

"One of the things I am most excited about with this award is that students are not simply assisting with the research; they are helping drive the discoveries," Renna said. "Laurence and Kendall have taken ownership of major pieces of these projects, and our undergraduate researchers are working alongside them. Taking research from discovery in the lab to presentation at an international scientific meeting is exactly the kind of experience we want to create for students at UA."

The award will support both the research and the training of undergraduate and graduate students as the Renna Lab works toward a more complete picture of the neural circuits that make vision possible.