Comparative and Computational Approaches to the Evolution of Myelin

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Rapid behavioral responses to a threat are critical for the survival of animals subjected to high predation risk. Two methods have evolved to shorten the delay between a threatening stimulus and an escape response, both by increasing the conduction velocity of nerve impulses along nerve axons: axon gigantism and myelin sheaths around the axons. Although myelin is best known in vertebrates, it is also found in two crustacean groups. These two invertebrate groups provide opportunities to understand structure-function relationships in myelin because: 1) it is possible to compare closely-related myelinated and non-myelinated forms; 2) nerve cells can be re-identified from one individual to the next, and 3) development of myelin can be tracked in identified cells through all developmental stages. In this project, physiological and computational approaches will be used in a comparative structure-function analysis of myelin in the two crustacean groups: the malacostraca and the calanoid copepods. Myelin has evolved independently in these two groups, yet it shares many features between the two, while being distinct in structure and origin. Some crustaceans transition from completely non-myelinated to fully myelinated nervous systems during development, and thus provide a good model in which to investigate nerve impulse conduction in incompletely formed myelin. Characterizing the commonalities in structure and function for myelin in copepods vs malacostracans will provide new insights into the function and evolution of vertebrate myelin. This study will start answering the question of how and why myelin evolved.The project will train young undergraduate scientists in interdisciplinary biology and team research, build diversity in science, technology, engineering and math; and provide public access to microscopic images for educational and data mining purposes. Postdoctoral trainees on the project will be educated in the preparation and examination of material for transmission electron microscopy, extracellular electrophysiological stimulation and recording techniques, and computational modeling of neuronal functioning.