Grant: Doctoral Award - Frederick Banting and Charles Best Canada Graduate Scholarships

Vision depends on our retina's ability to translate light into a neural code. This translation occurs at the level of our photosensitive cells, ('photoreceptors'), which contain specialized light-sensitive pigments, called opsins. In many blind individuals, these photoreceptors progressively degenerate, leading to a loss of vision. Surprisingly, however, many visual responses such as day/light cycles and pupillary reflexes remain intact in blind individuals. We currently have an incomplete understanding of which cells in the retina mediate these residual visual responses. Our research team has recently discovered two separate cell populations present in mice and humans which express the same opsins as photoreceptors, yet reside in an entirely separate layer of the retina. We hypothesize that these cells may be partially responsible for the residual visual responses present in blind individuals. To test this, we will record directly from these cells to examine whether they respond to light. Then, we will examine the role of these novel opsin expressing cells in the residual light responses of photoreceptor-degenerated blind mice, by deleting these opsins from the retina. This will tell us whether these novel cells are indeed an important mediator of visually-driven behavior in mice. Understanding the full complement of light-responsive cells in the retina has widespread implications in the treatment of degenerative retinal diseases. Over one million Canadians are living blind or partially sighted, and this number is expected to double over the next 25 years. Those with degenerative retinal diseases experience a progressive loss of photoreceptor cells, and recent innovative approaches have attempted to restore vision to mice lacking photoreceptors by stimulating non-photoreceptor cells with light. Gaining a complete understanding of the retina's photoreceptive network, which may include these novel cells, is imperative for the implementation of these approaches.