9805900 HOSKINS In the study funded by this POWRE award, Dr. Hoskins will examine the molecular basis of changes that occur in the frog eye during metamorphosis. The eyes of young tadpoles are situated on the sides of the head and the two eyes view non- overlapping regions of the visual world. During metamorphosis, the head changes shape, and the eyes move together, with the result that adult frogs have binocular vision -- parts of the visual world are seen with both eyes, as is the case in humans. During the transition from tadpole to frog, which is brought about by thyroid hormone, numerous changes occur both within the eye and in the connections between the eye and the brain. Previous work from the Hoskins laboratory showed that thyroid hormone induces a specific new pattern of retinal growth, and that a new set of optic nerve axons are produced during metamorphosis. These new studies will address the question of how thyroid hormone triggers changes in retinal growth, and how the new axons formed during metamorphosis are able to connect to their proper targets, which differs from the pattern of connections made by tadpole axons. Thyroid hormone acts through a receptor that is capable of changing the pattern of gene expression; it therefore seems likely that hormone-induced genes expressed in the retina will play a role in the metamorphic transformations in the visual system. The nervous systems of all animals, including humans, are dependent on thyroid hormone for proper development. Dr. Hoskins' experimental system offers a uniquely accessible and manipulable model for examining the mechanisms of thyroid hormone action during development, and the results of these studies are expected to be relevant to its general roles in neuronal development. This POWRE award will allow an excellent investigator with substantial teaching duties to begin a research project using new molecular methodology on a system and a question with in which she has had a long -standing interest.
