Using C. elegans to investigate the transgenerational effects of ethanol and to genetically repair a gait transition impairment in dopamine-deficient animals




Guzman, Dawn Marie

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The nematode Caenorhabditis elegans offers several valuable tools for studying a range of topics in neuroscience and genetics. In this thesis, I specifically exploited the genetic tractability, short generation time, and well-characterized locomotor behaviors of this roundworm to carry out two different projects. For my first project, I investigated the transgenerational effects of ethanol exposure in C. elegans. Parental exposure to certain environmental triggers (stress, toxins, etc.) can alter the phenotypes of unexposed offspring, sometimes persisting for multiple generations. Because alcohol use disorders in humans have a heritable component which is not yet fully understood, I set out to test the effects of ethanol (EtOH) exposure on EtOH sensitivity in subsequent generations. We tested nine cohorts that included an EtOH line derived from female hermaphroditic worms continuously exposed to 24 hours of EtOH during beginning adult stage, as well as a Control line derived from untreated worms. We found that first, second and third generation worms (F1-F3) in the EtOH line showed a minor trend toward resistance to intoxication relative to the Control line. We also tested four cohorts exposed to EtOH for the same time window but intermittently, and found that worms in the EtOH line showed a trend towards hypersensitivity relative to control. I discuss the complexities of these weak transgenerational inheritance patterns, and how they may be influenced by environmental, timing and testing factors to be considered for future investigations. For my second project, I uncovered novel mutations that suppressed a locomotor defect in dopamine-deficient worms. Without dopamine, these worms exhibit motor deficits analogous to those in humans with Parkinson’s Disease. Dopamine-deficient mutant worms are temporarily immobilized when attempting to transition from swimming to crawling. By conducting a forward genetic screen on the dopamine-deficient mutant cat-2, I isolated new mutants that suppressed the abnormal motor transition in these animals. Further behavioral and pharmacological characterization of dopamine-dependent phenotypes of these cat-2 suppressor (ctsp) mutants suggests how their physiology may be altered to suppress the motor transition defects. Future mapping and cloning of the causal suppressor mutations may reveal new targets for treating Parkinsonian motor deficits.



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