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Poster Full Abstracts - Drosophila Models of Human Diseases
Poster board number is above title. The first author is the presenter
244
Screen for common genetic modifiers of polyglutamine diseases in Drosophila.
Javier R Diaz, Ismael Al-Ramahi, Juan Botas. Molecular and Human
Genetics, Baylor College of Medicine, Houston, TX.
Polyglutamine diseases are caused by expansion of a CAG repeat within the coding region of the disease-causing gene. Two of the nine known
polyglutamine disorders are Spinocerebellar Ataxia type 1 (SCA1) and Huntington's disease (HD). The proteins affected in these two disorders are Ataxin-1
and Huntingtin respectively. Using Drosophila as a model system, we carried out genetic screens of all genes encoding kinases for potential modifier genes
of SCA1 and HD. In the SCA1 Drosophila model we drive expression of mutant Ataxin-1 (SCA182Q) to the eye using gmr-Gal4 and we analyze the
external structure of the eye. In the HD model, we drive the expression of mutant huntingtin (N-terminal Htt128Q) to the nervous system using elav-Gal4
and we assess motor performance using a climbing assay. As a result of these screens we obtained common modifier genes. Some of these modulate SCA1
and HD similarly, whereas other modifier genes modulate them antagonistically (e.g., suppressor vs. enhancer). We are currently analyzing the mechanisms
by which these modifiers modulate disease phenotype; these studies include analyzing steady-state levels of the disease-causing protein, investigating
mitochondrial/bioenergetic alterations, and assessing Ca2+ levels.
416B
The role of Swiss cheese, the
Drosophila
homologue of Neuropathy target esterase, in glia development.
Sudeshna Dutta
1,2
, Doris Kretzschmar
1
. 1)
Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, OR; 2) Department of Integrative
Biosciences, Oregon Health and Science University, Portland, Oregon.
Neuropathy target esterase (NTE), a molecular target of organophosphates (OP) found in pesticides and nerve gases induce delayed neuropathy (OPIDN)
in humans. OPIDN is characterized by axonal degeneration mainly of motoneurons. Similarly, loss of the Drosophila homologue of NTE, Swiss Cheese
(SWS) causes progressive neurodegeneration in flies but also glial degeneration. Previously we have shown a cell autonomous requirement of SWS in both
neuronal and glial cell types in the adult brain of
Drosophila
. Using cell type specific down regulation of SWS, we can now specifically address its
requirement in glia. We are also investigating the importance of various functional domains of the trans-membrane protein SWS in the glia specific
phenotype. Our recent findings in mouse show presence of SWS/NTE in astrocytes in the sciatic nerve, suggesting a conserved role of SWS in glia in higher
vertebrates. These studies, using both
Drosophila
and mouse model systems, will help us to understand the importance of the SWS protein in glia, its
regulation in axonal-glial interaction and its pathogenic function in inherited spastic paraplegia and in OPIDN in humans.
417C
Oxidative Stress in a Drosophila Model of TPI deficiency.
Isaac J Fisher
1
, Daniel Long
1
, Joshua Hutton
1
, Zhaohui Liu
1
, Sarah Johnson
1
, Michael J
Palladino
2
, Stacy L Hrizo
1,2
. 1) Department of Biology, Slippery Rock University, Slippery Rock, PA; 2) University of Pittsburgh S.O.M. Department of
Pharmacology and Chemical Biology, Program in Neurodegenerative Diseases, Pittsburgh, PA.
Triose phosphate isomerase (TPI) is responsible for the interconverstion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate in the glycolytic
pathway. Point mutations in the gene encoding this enzyme are associated with a glycolytic enzymopathy called TPI deficiency. This study focuses on
TPI[sgk]
, a mutant allele with a missense mutation (M80T) that causes phenotypes in Drosophila melanogaster similar to that of TPI deficiency in humans.
The pathology of TPI deficiency is still poorly understood. In this study, we examine the redox status of flies with the
TPI[sgk]
mutant allele in order to
better understand the pathology of this disease. We hypothesized that
TPI[sgk]
animals would have sensitivity to oxidative stress due to the higher levels of
the oxidized forms of various redox molecules. Supporting this, we examined the ratios of the reduced and oxidized forms of NAD+, NADP+, and
glutathione. It was determined that
TPI[sgk]
animals exhibit higher levels of the oxidized forms of these molecules in an age dependent manner. In addition,
we tested the effect of oxidizing and reducing stressors on the behavioral phenotypes of the
TPI[sgk
] animals. It was found that reductive stress improves the
behavioral phenotypes of the mutant organism while oxidative stress worsens these phenotypes. In addition, we examined the stability of mutant protein
when animals were treated with oxidizing and reducing stressors and determined that TPI[sgk] protein levels were unaffected by redox stressors. Overall,
this data suggests that reduced activity of TPI causes an increase in oxidative stress in the organism and that alleviating this stress with reducing compounds
improves the mutant phenotypes.
418A
Sleep defects in Drosophila models of Huntington’s Disease reflect altered PKA signaling.
Erin D Gonzales
1,2
, Jerry C-P Yin
1,3
. 1) Dept. of Genetics,
University of Wisconsin-Madison, Madison, WI; 2) Program in Cellular & Molecular Biology, University of Wisconsin-Madison, Madison, WI; 3) Dept of
Neurology, University of Wisconsin-Madison, Madison, WI.
Identification of early biomarkers of neurodegenerative diseases is essential to understanding early pathogenesis and developing therapeutic strategies.
Studies in HD carriers show disturbances in sleep are among the earliest quantifiable symptoms and correlate with cognitive changes, indicating sleep
changes may be used as a biomarker for early disease and testing of potential interventions. Drosophila HD models recapitulate many cell and molecular
phenotypes of HD and mammalian HD models, showing that pathways mediating pathogenesis are conserved. These phenotypes include alterations in
transcription, intracellular trafficking, metabolic regulation, & motor function. Using pan-neuronal drivers C155 or G28 elav-Gal4 with full-length
(mutHttFL) and truncated mutHtt (mutHttNterm), our goals were: 1) to determine whether Drosophila HD models exhibit perturbations in sleep & activity
similar to those in HD carriers & 2) to identify the underlying pathways. Pan-neuronal expression of mutHttNterm by C155 normally results in pupal
lethality, whereas G28 expression results in adult viability. We show that mutHttFL & mutHttNterm flies exhibit abnormal sleep and activity patterns. These
changes in sleep architecture and activity precede other systemic phenotypes and resemble deficits in human patients. Treatment with a dopaminergic
signaling inhibitor reverses these alterations. This reversal, along with a dramatically reduced sensitivity to caffeine, are consistent with abnormally elevated
PKA in HD flies. We show that RNAi against PKA catalytic subunits or overexpression of a PKA regulatory subunit rescues C155-driven lethality, and
restores normal sleep patterns when driven by G28. We also show biochemical & imaging data that baseline levels of cAMP and phospho-CREB are
elevated brain-wide in HD flies compared to controls. Our data indicate that cAMP/PKA signaling is dysregulated early in HD and that this pathway may
present a target for therapeutics.
419B