Circuits attenuating seizures under well-fed and food-deprived conditions in C. elegans male sex muscles
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The circuits that allow organisms to control behavioral timing need to be tightly regulated to ensure execution of appropriate environmental responses. Disrupting such regulation results in individuals unable to perform tasks necessary for survival and propagation. Identifying the molecular components regulating behaviors will enable compensation where behavioral impediments to survival exist. To identify circuits of behavioral regulation, I studied male mating behavior in the nematode Caenorhabditis elegans. Specifically, I focused on the step wherein the male inserts his copulatory spicules into the hermaphrodite vulva, as vulva penetration is required for successful sperm transfer. This step must be tightly regulated; if the spicules protract too soon or not at all, vulva penetration and thus successful mating will not occur. In this dissertation, I elucidate the circuits regulating sex-muscle excitability under standard conditions and describe how these pathways are augmented to further reduce excitability under food deprivation conditions. I employ a variety of assays to identify and analyze these circuits, including genetic manipulation, biochemical techniques, and behavioral assays. Under standard conditions the calcium/calmodulin-dependent protein kinase II (CaMKII) encoded by unc-43 is required to inhibit C. elegans male sex-muscle seizures; under conditions where food is scarce, I propose that CaMKII is further up-regulated to activate the EAG K+ channel EGL-2 through a direct interaction. The CaMKII/EGL-2 interaction functions to attenuate calcium influx from L-type voltage-sensitive calcium channels (L-VGCCs), while CaMKII also downregulates calcium influx from ryanodine receptors. Additionally, another K+ channel, the voltage- and calcium-sensitive big current channel SLO-1, attenuates sex-muscle excitability by inhibiting L-VGCCs under food deprivation conditions. In conclusion, CaMKII and EGL-2?s paralog, UNC-103/ERG-like K+ channel, are required when food is plentiful to prevent premature sex-muscle contractions, while food deprivation reduces cell excitability and thereby inhibits inappropriate seizures through CaMKII, EGL-2, and SLO-1.
Leboeuf, Brigitte L. (2009). Circuits attenuating seizures under well-fed and food-deprived conditions in C. elegans male sex muscles. Doctoral dissertation, Texas A&M University. Available electronically from