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Candidate gene and high throughput genetic analysis of habituation in Caenorhabditis elegans Giles, Andrew Christopher

Abstract

The goal of my dissertation was to identify genes that are important for habituation (a decrease in response to a repeated stimulus) with the hope of bringing us closer to understanding the cellular and molecular mechanism that mediates this basic form of learning. To accomplish this I studied habituation of the tap withdrawal response in Caenorhabditis elegans; an organism with a tractable nervous system, well characterized habituation and availability of genetic tools and resources that make it easy to investigate the mechanisms of behaviour. Two approaches were taken. The first was a candidate gene approach where I investigated mutations in genes important for dopamine neurotransmission. A previous study showed that dopamine deficient and dopamine receptor mutants have abnormal habituation and the dopamine receptor is expressed within the tap sensory neurons. Investigating this effect more closely, I found that short-term tap habituation in C. elegans was dependent on the presence of E. coli (their food) and that this food-dependent modulation of habituation was dopamine dependent. The second approach involved characterizing habituation of a large set of C. elegans strains with known mutations in genes predicted to function in the nervous system. Many of these mutants had not previously been characterized. To accomplish this task, it was necessary to improve the speed and detail with which habituation can be assayed. In collaboration with the Kerr Lab at Janelia Farm Research Campus, we developed a high throughput C. elegans behavioural tracking system called the Multi-Worm Tracker. Using this tracking system, I examined many mutants and discovered hundreds of novel phenotypic variants for habituation in C. elegans. The genes affected by these mutations can now be investigated in more detail in order to identify the role that they play in the molecular and cellular mechanism of habituation.

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