The discovery provides a new vantage point for understanding how a healthy visual system develops. It also raises the possibility of re-directing the production of cell types as needed to stave off eye disease.
The study reports on the role of the gene regulator NRL, which was previously shown to be essential for the development of rods, the light-sensing cells required for vision.
Anand Swaroop, Ph.D., Harold F. Falls Collegiate Professor of Ophthalmology and Visual Sciences and Professor of Human Genetics, is senior author of both studies, the latest of which appears in the March 7 issue of the Proceedings of the National Academy of Sciences (PNAS).
In PNAS, Swaroop's team reports that NRL is the earliest marker of rod precursors, or cells that are fated to become rods. They achieved this unique and early view of rod development by creating a mouse model using an NRL regulatory DNA sequence to produce a protein that appears as fluorescent green when exposed to blue light. This fluorescent protein allows scientists to identify even a few cells that are destined to be rods at very early stages of development.
"For the first time we were able to see retina cells during early development, allowing us to pinpoint the exact time at which rods are 'born,'" says Swaroop. "Because the cells have been tagged, we can watch them at each step as they develop into mature and functional rods." Kellogg scientists then purified the rods at various stages and generated the profile of genes at each stage. This, for the first time, provided a handle for investigating the precise process of rod differentiation.