ANN ARBOR, MI - A paper published electronically this week by Nature Genetics offers important new insights into the development and differentiation of rod and cone photoreceptors, the light-sensitive cells in the eye's retina that initiate vision and are essential for clear sight.
A team led by Anand Swaroop, Ph.D., professor of ophthalmology and vision research scientist at the University of Michigan Health System's Kellogg Eye Center, has demonstrated that the retinal protein Nrl is required for rod development and, in fact, acts as a "molecular switch," signaling the cells to develop into rods rather than cones.
Working with Swaroop, research investigator Alan J. Mears, Ph.D., deleted the gene that makes Nrl in mice, creating an Nrl-knockout strain that developed a retina without rod photoreceptors.
"These findings are important because they will allow us to understand how rods are formed, and more importantly how we can save the cones," says Swaroop. "Currently, the cellular pathways and regulatory molecules that determine exactly how photoreceptors develop are poorly understood. If we learn more about this process, we may be able to pinpoint ways to intervene with gene or drug therapy to treat certain types of vision loss."
A better understanding of rods and cones may help researchers treat retinitis pigmentosa (RP) and macular degeneration, two major eye diseases that involve loss of photoreceptors, resulting in slow but progressive vision loss.
Swaroop explains that photoreceptors are post-mitotic cells; meaning that when they degenerate, they cannot be replaced and a person's vision suffers. Cone photoreceptors enable color vision and visual acuity in bright light. Rods, which dominate the retina, are responsible for night vision.