PH10 Soil Ecotoxicology and Risk Assessment
Exhibit Hall
8:00 AM - Thursday
(PH132) Iron toxicity in the nematode Caenorhabditis elegans: the effects of decreased frataxin on growth, reproduction, mitochondrial DNA damage, and gene expression.
Boyd, W1, Meyer, J2, Haugen, A2, Van Houten, B2, Freedman, J1, 1 Duke University, Durham, NC, 277082 National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709
ABSTRACT- Although iron is an essential element and is ubiquitous in the environment, at excessive free levels it can become toxic due to its role in the formation of reactive oxygen species (ROS), which can lead to damage of proteins, cellular membranes, and DNA. As with all essential elements, iron homeostasis is tightly regulated in order to prevent both deficiency and toxicity. In humans, decreased levels of the mitochondrial protein frataxin cause increases in free iron and H2O2 levels leading to degeneration of neurons and cardiomyocytes in a disorder termed Friedreich's ataxia. The frataxin gene is highly conserved making it possible to use the nematode Caenorhabditis elegans as a model to investigate frataxin function in vivo. RNAi knockdowns of frataxin as well as a mutant strain (VC389) maintained as a heterozygous population (frh-1 +/-) are being used to investigate the effects of decreased frataxin levels in C. elegans. Semiquantitative PCR results indicate that frataxin levels are decreased in VC389 worms as compared to wildtype N2 worms. Although C. elegans has been used to investigate the toxicity of many metals, few reports of iron toxicity exist. Initial sublethal toxicity tests including growth and reproduction indicate that mutant VC389 worms are more sensitive to iron exposure than are wildtype worms. Furthermore, preliminary data indicate that VC389 nematodes show increased mitochondrial DNA damage relative to wildtype nematodes as assessed by a long PCR-based assay we have recently adapted for use in this organism. We will present the details of the development and validation of this assay and its use in measuring nuclear and mitochondrial DNA damage and repair. Finally, we are currently comparing gene expression in VC389, RNAi knockdowns of frh-1, and wildtype C. elegans.
Key words: iron, Caenorhabditis elegans, frataxin, ROS