RUI - Nitric Oxide Inhibition of Metamorphosis in a Marine Snail

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During development, the cells of the nervous system go through periods of growth and proliferation and are often produced in excess. As cells become connected into their adult circuits, excess cells and cells in temporary structures die and are removed by a naturally occurring process called apoptosis. This process is regulated, in part, by diffusible signaling molecules that also act as neurotransmitters in adults. Neurotransmitters are small compounds that nerve cells use to communicate with each other. One such molecule is the diffusible gas, nitric oxide. Once inside a cell, the interaction of nitric oxide with its target molecule sets off a cascade of biochemical events. While nitric oxide has been implicated in regulating both cellular proliferation and apoptosis, little information exists about its role in the regulation of nervous system development. Previous work in Dr. Leise's laboratory has indicated that nitric oxide acts as a natural inhibitor of metamorphosis in a species of marine snail. During this process, one cluster of neurons in the brain, the so-called apical ganglion, disappears. Drs. Leise and Hens hypothesize that the disappearance of this ganglion is a result of apoptosis. They will use a histochemical test to look in apical ganglion cells for the presence of DNA fragments which form during apoptosis. They will also conduct related pharmacological and anatomical investigations to determine if nitric oxide regulates this process. They will investigate the relationship of nerve cell proliferation to metamorphosis and will determine if nitric oxide also controls the birth of new neurons. Finally, they will use molecular and immunocytochemical methods to identify regions of the embryonic brain that produce the enzyme that generates nitric oxide and determine when the production of the enzyme, and thus nitric oxide, cease during development. Nitric oxide occurs naturally as a neurotransmitter in the brains of adult humans, and its importance in the function of the adult brain is widely accepted. However, little is known about the role of this important molecule in embryonic development. These studies will further our understanding of nitric oxide in the embryonic brain and its importance for the regulation of neural development.