Characteristics of Photoreceptor and Bipolar Cell Nuclei in the Skate Retina
By: Aya Alazzeh and Daniel Brown
Department: Physiology
Faculty Advisor: Dr. Ivan Anastassov
The retina is a sensory tissue lining the back of the eye and its main function is to convert light into electrical signals. It typically contains two photoreceptor kinds: rods, which detect dim light, and cones, which detect bright light and color. Our model organism, a fish called Little skate, has a retina that is unique in that it lacks cones – that is, it exclusively contains rods as its photoreceptor type. For our project, we are investigating the nuclei within photoreceptors (Daniel) and bipolar cells (Aya) in order to identify their distinguishing characteristics, like size, shape, and budding patterns. These characteristics may give us insight into how neurons in the skate retina are arranged or stacked, and allow us to compare these hallmarks to the retinas of animals that have both rods and cones. To examine photoreceptors and bipolar cells, retinal tissue from skate was imaged using serial section electron microscopy. Using Reconstruct software, we were able to trace our respective nuclei and create 3D models of them. We observed a somewhat uniform size, shape, and spacing between nuclei downstream of photoreceptors (likely belonging to bipolar and horizontal cells). Additionally, nuclei downstream of photoreceptors seem to orient themselves into two columns. Exceptions to the uniformity included nucleus 15, which bud off into two separate structures, a vesicle being found between the two. The organization of the nuclei that are present in photoreceptors are stacked in columns with relatively similar morphology from one to the next. Slight differences that appear between these nuclei present themselves in the splitting of a single nucleus into a fork-like structure, but there is no divergence of the single nuclei into two separate structures. Our work will help us understand the organizational structure of cells within the pure-rod retina of skate and can contribute to future vision restoration efforts.