Cone Arrestin



Photoreceptor signal transduction





Research Objectives

      Vertebrate rod and cone photoreceptors hyperpolarize in response to light using cell-specific proteins to drive a phototransduction cascade of common design. Close inspection reveals that rods differ significantly from cones in morphology, light sensitivity, color responsivity, recovery rate, outer segment shedding timing and resistance to cell death by pathway is unresolved. Dr. Craft with her longtime collaborator, Dr. R.N. Lolley, and their research team have identified key photoreceptor components and have contributed to the knowledge of the molecular and biochemical mechanisms underlying the initial steps in the rod pathway.  Further clarification of the cone photoreceptor cascade is the next step. The Mary D. Allen Laboratory for Vision Research group is now focusing on the cone-specific genes and products. They will first systematically use molecular, biochemical and electrophysiological approaches to characterize cone arrestin, a homologue of rod arrestin that binds and shuts off activated, phosphorylated rhodopsin.

     Dr. Craft and her collaborators will examine the contribution of cone arrestin (CAR) to the cone phototransduction cascade in a multi-step process. First, cone arrestin will be targeted for genetic disruption to evaluate cone photoreceptor structure and function. Second, the CAR KO mice will be crossed with the neural retina leucine zipper KO (Nrl KO) mice to create a CAR/Nrl double KO mouse model to characterize the phenotypic changes in cone cell morphology, electrophysiology, and phototransduction kinetics. The Nrl KO mice, created and provided by Dr. Anand Swaroop's laboratory, have retinas that lack rods, express pure-cones and "supernormal" electrophysiological cone function. Third, Dr. Craft will explore potential functional partners of cone arrestin using a yeast two-hybrid screen with a mouse retina library. Fourth, a Xenopus retinal model will be used to identify the molecular signature for cone expression.

     It is imperative that our knowledge of cone-specific genes and proteins and their individual activities be brought to the level of sophistication as exist now for rods. The reward of this knowledge will provide the basis for understanding how the photoreceptors of the retina function and why cone photoreceptors are so different from rods. In turn, expanding our understanding of the scope and complexity of cone activities will provide a solid foundation for making choices about maintaining normal high acuity vision. Moreover, knowledge of G protein coupled receptor signaling pathways will assist in resolving the molecular interactions that control the communication and maintenance of cell.

     Although the mechanisms underlying sensory transduction, tissue-specific gene expression and protein function are keys to our understanding of how the retina works, the active introduction and participation in our research program with high school, undergraduate, graduate and medical student researchers is critical. As a grateful high school recipient of the NSF research apprentice program in the 60's, Dr. Craft was introduced and chose a basic science research career. Her long-term goals include preparing the next generation of scientist and physicians for future research careers. The broader impacts of the project include the integration of the advancement of knowledge and education for our future scientists, informed citizens, and government agencies in understanding the elements involved in basic and clinical science research.