Evaluating Contributions of DAT-1 and FKH-8 to Dopaminergic Neuron Degeneration through Oxidative Stress

Graduate #17
Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology

Casey M. Paton - Fisk University
Co-Author(s): Brian Nelms, Nashville, TN

Dopamine is a neurotransmitter synthesized in the substantia nigra and ventral tegmental areas of the brain. Dopamine is involved in motor control, reward pathways, pleasure, and addiction; misregulation of dopamine signaling is associated with conditions such as Parkinson’s disease, schizophrenia, and ADHD. An auspicious potential treatment for such disorders is the cultivation of dopaminergic neurons for transplantation; but damaging physiological conditions such as high oxidative stress pose a formidable challenge. Dopaminergic neurons are particularly susceptible to degeneration through oxidative stress, which stimulates interest in . High levels of manganese have been shown to cause motor deficits similar to those exhibited in Parkinson’s disease (1). Manganese is known to accumulate in the basal ganglia of the brain but a complete mechanism of manganese neurotoxicity has yet to be elucidated (2). My preliminary data shows that Caenorhabditis elegans lacking the novel transcription factor Forkhead Eight (fkh-8), treated for thirty minutes with 50mM or 100mM MnCl2, exhibited increased neurodegeneration (shown by blebbing and loss of GFP fluorescence in CEP neurons). My preliminary aging studies suggest that fkh-8 deletion mutants show increased mortality at intermediate time points. We are considering regulation of the genes encoding the SMF-1 and SMF-2 manganese transporters by FKH-8 as a potential source of these mechanisms; is the increased sensitivity to manganese-induced neurodegeneration and increased mortality in natural aging exhibited by fkh-8 mutants occurring through changes in the amount or activity of the SMF-1 or SMF-2 manganese transporters? I have crossed strains to engineer fkh-8; smf-1 and fkh-8; smf-2 double mutant worms to test if the neurodegeneration caused by MnCl2 treatment is different in either of these mutants lacking the SMF transporter. If so, this would suggest the SMF-1 or SMF-2 manganese transporters are altered upon loss of FKH-8, which leads to subsequent exacerbation of CEP neuron degeneration. This research is important to characterize the molecular aspects and transcriptional regulation of manganese toxicity and dopaminergic control; such knowledge is critical to understand proper neuronal function and to develop treatments for Parkinson’s disease, Schizophrenia, and ADHD.

Funder Acknowledgement(s): NSF grant #1500320, Tennessee LSAMP Bridge to the Doctorate Program at Vanderbilt University

Faculty Advisor: Brian Nelms, bnelms@fisk.edu

Role: I have been involved in all aspects of project design, experiment execution, and data analysis. I have spent the last twelve months optimizing the manganese and juglone exposure protocols. I have performed over a dozen experiments to determine a functional assay. I have subsequently performed four manganese trials, five juglone trials, and eight aging trials for data acquisition. I image the C. elegans and provide a quantitative value of 0 or 1 for neurodegeneration. I then graph the data and compare variance between genotypes with a Fischer's Chi Square analysis, 2 way ANOVA. I have also performed various crosses for new strains of C. elegans. I am involved in all aspects of stock maintenance, project execution, data analysis, and consideration of future directions.