ADrosophilamodel to investigate the neurotoxic side effects of radiation exposure

Abstract

Children undergoing cranial radiation therapy (CRT) for pediatric central nervous system malignancies are at increased risk for neurological deficits later in life. We have developed a model of neurotoxic damage in adult Drosophila following irradiation during the juvenile stages with the goal of elucidating underlying neuropathological mechanisms and of ultimately identifying potential therapeutic targets. Wild-type third-instar larvae were irradiated with single doses of γ-radiation, and the percentage that survived to adulthood was determined. Motor function of surviving adults was examined with a climbing assay, and longevity was assessed by measuring lifespan. Neuronal cell death was assayed by using immunohistochemistry in adult brains. We also tested the sensitivity at different developmental stages by irradiating larvae at various time points. Irradiating late third-instar larvae at a dose of 20 Gy or higher impaired the motor activity of surviving adults. A dose of 40 Gy or higher resulted in a precipitous reduction in the percentage of larvae that survive to adulthood. A dose-dependent decrease in adult longevity was paralleled by a dose-dependent increase in activated Death caspase-1 (Dcp1) in adult brains. Survival to adulthood and adult lifespan were more severely impaired with decreasing larval age at the time of irradiation. Our initial survey of the Drosophila Genetic Reference Panel demonstrated that differences in genotype can confer phenotypic differences in radio-sensitivity for developmental survival and motor function. This work demonstrates the usefulness of Drosophila to model the toxic effects of radiation during development, and has the potential to unravel underlying mechanisms and to facilitate the discovery of novel therapeutic interventions.

Genome-wide analysis reveals distinct genetic mechanisms of diet-dependent lifespan and healthspan inD. melanogaster

“…Because walking speed is frequently used as a marker of health and a predictor of mortality in humans (79, 80), we utilized flies’ natural tendency to climb their enclosure to track negative geotaxis performance in 156 DGRP lines throughout the duration of their life in parallel to measuring lifespan, as described above. We measured the percentage of each line able to climb an empty vial wall once per week throughout adulthood (81–83) (detailed in Methods). As an index of health decline, we analyzed the day at which a given DGRP strain fell below 50% of its initial climbing ability.…”

Distinct aging-vulnerable trajectories of motor circuit functions in oxidation- and temperature-stressedDrosophila

“…Rearing flies at 29°C is a widely adopted protocol for experimental expedience in Drosophila aging and neurodegeneration studies ( e.g. Min and Benzer (1997); Kang et al (2002);Simon et al (2003);Biteau et al (2010);Sudmeier et al (2015)) . Our study directly investigated the impact of rearing at 29 49°C on different motor functions over the lifespan, and the cellular physiological links between proposed molecular mechanisms (Harman, 1956;Finkel and Holbrook, 2000;Ziegler et al, 2015) and behavioral alterations previously described for Sod mutant flies.…”

Persistent Activation of the Innate Immune Response in AdultDrosophilaFollowing Radiation Exposure During Larval Development

“…Larval irradiation was performed as described in Sudmeier et al (2015) . Briefly, wandering third instar larvae were collected, counted, and transferred to fresh culture vials (30–50 larvae per vial).…”

“…Brains were dissected, stained, and imaged as described in Sudmeier et al (2015) . The antibodies used are as follows: Chicken anti-Green Fluorescent Protein (Life Technologies, Carlsbad, CA; 1:500), Mouse anti-Repo (Developmental Studies Hybridoma Bank, University of Iowa, Iowa City, IA; 8D12, 1:50), Rat anti-Elav (Developmental Studies Hybridoma Bank, University of Iowa, Iowa City, IA; 7E8A10, 1:250), DAPI (Sigma-Aldrich, St. Louis, MO; 1 mg/L), Goat anti-Chicken Alexa Fluor-488 (Life Technologies, Carlsbad, CA; 1:200), Goat anti-Mouse Alexa Fluor-568 (Life Technologies, Carlsbad, CA; 1:200), and Goat anti-Rat Alexa Fluor-633 (Invitrogen, Carlsbad, CA; 1:200).…”

“…We recently developed a Drosophila model of the long-term neurotoxic side effects of radiation exposure during development ( Sudmeier et al 2015 ). This model demonstrates that in flies, as in human patients who undergo CRT for pediatric malignancies, there are long-term effects in the adult, such as impaired neurological function and cellular changes in the brain.…”