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Poster Full Abstracts - Drosophila Models of Human Diseases
Poster board number is above title. The first author is the presenter
247
members of the Tor signaling pathway were identified as modulating viability in the presence of metals. In addition, the results of our initial RNAi
experiments suggest that a putative P-type ATPase cation transporter plays a general role in cation import. Specifically, we found that RNAi knockdown
with either of two different dsRNAs directed against the putative transporter prevents cells from benefiting from the positive effects of low-level metal
supplementation and conversely protects cells from the toxic effects of high-level metal supplementation. Intriguingly, the transporter is highly related to a
mammalian protein associated with Parkinson’s disease. Our results suggest that RNAi screening in cultured
Drosophila
cells is an appropriate platform for
identification of new genes involved in metal homeostasis and/or toxicity and further, that the results of these studies may impact our understanding of
neurodegenerative and other diseases. Efforts to develop
in vivo
assays of metal toxicity for validation are ongoing.
427A
The Etiology of Brain Degeneration in drd Mutant Flies.
Sreejith Perinthottathil, Wijeong Jang, Jiyoung Kim, Changsoo Kim. Chonnam National
University, Gwangju, South Korea.
The Drosophila drop-dead (drd) mutant undergoes massive brain degeneration. The etiology of brain degeneration in drd mutant flies is still unknown. We
found that DRD protein is selectively expressed in cells secreting cuticular and eggshell layers that exhibit blue fluorescence upon UV excitation, which is
reduced in drd flies. We found that the drd tracheal air sacs lacking blue fluorescence collapse and genes induced in hypoxia are up-regulated in drd flies.
Feeding of anti-ROS agents partially rescued the drd from sudden death. We propose that drd flies can provide a non-invasive animal model for hypoxia-
induced cell death.
428B
Identification of protective and pathogenic residues in the prion protein.
Jonatan Sanchez-Garcia, Daniela Arbelaez, Kurt Jensen, Yan Zhang, Diego
Rincon-limas, Pedro Fernandez-Funez. Department of Neurology, Univ of Florida, Gainesville, FL.
Prion diseases are transmissible neurodegenerative diseases caused by misfolding of the prion protein (PrP) into pathogenic conformations. Unfortunately,
major gaps still exist in the knowledge of how PrP undergoes conformational changes. We have shown previously that transgenic flies faithfully reproduce
the structural dynamics of pathogenic and stable PrP sequences. Here, we describe point mutations in loop 2 and helix 3 with dramatically opposing effects
on PrP structural dynamics. Dog PrP possesses a globular domain with a highly stable tertiary structure. We identified a charged amino acid in loop 2 of dog
PrP (D158) that is not conserved in other mammals (N158). To test if D158 could increase PrP stability, we introduced the N158D substitution in mouse
PrP. PrP-WT accumulates in pathogenic isoforms but PrP-N158D does not, supporting its higher conformational stability. Also, PrP-N158D does not induce
the aggressive locomotor dysfunction observed with PrP-WT, indicating that the N158D substitution is neuroprotective. We also investigated the
consequence of destabilizing helix 3, which has been proposed to initiate PrP misfolding. For this, we introduced two Met, to Ser substitutions in helix 3 that
destabilize key hydrophobic interactions in the globular domain. Surprisingly, the M205,212S substitutions affected not only PrP folding, but also its
processing and topology. PrP is anchored to the plasma membrane by a GPI. However, PrP-M205,212S resulted in an abnormal transmembrane topology
(CtmPrP) that plays a role in disease. Consistent with CtmPrP, PrP-M205,212S retained it signal peptide and produced a protease resistance fragment. PrP-
M205,212S also induced aberrant development of mushroom lobes, showing that it is neurotoxic. Overall, this work identifies key residues in loop 2 and
helix 3 with dramatic effect in the stability of the globular domain. These studies may provide critical information for the development of anti-prion
therapies.
429C
Tau-induced neurotoxicity and apoptosis in a Drosophila model.
Tzu-Kang Sang
1
, Chien-Ping Hsieh
1
, Ren-Huei Shiu
1
, Hui-Yun Chang
2
. 1) Institute of
Biotechnology, National Tsing Hua University, Hsinchu, Taiwan; 2) Institute of Systems Neuroscience,, National Tsing Hua University, Hsinchu, Taiwan.
Tauopathies are characterized by the intraneuronal deposit of fibrils that containing hyperphosphorylated tau in human brain. Tau is a microtubule-
associated protein, which stabilizes the microtubules cytoskeleton and regulates the dynamic of tubulin assembly. Recent studies have demonstrated that
mutations in certain sites of tau that derived from autosomal dominant tauopathy FTDP-17 (frontotemporal dementia with parkinsonism linked to
chromosome 17) could lead to hyperphosphorylated tau aggregates in the neurons. While Tau protein phosphorylation is the major focus on tauopathies
studies, several reports found that tau-induced cytotoxicity could be uncoupled with its phosphorylation state. Here, we have employed a well-characterized
Drosophila model of tauopathy to investigate whether the toxicity of tau is due to the cleavage by Caspases. Overexpression of human tau recapitulates the
features of tauopathies, and the phenotype could be suppressed by RNA interference (RNAi)-mediated knockdown of selected Drosophila Caspases. In
addition, expressing tau that insensitive to the Caspase cleavage resulted only mild neurodegeneration as compared to that over expressing wild type Tau.
These data support that processes of tau by caspase is crucial for the tau-mediated cytotoxicity. Furthermore, we also evaluated fly tau ortholog CG31057 in
which has preserved microtubule-binding domains but lack of the putative Caspase cleavage sites. In our analysis in the visual system, fly Tau appeared to
be dispensable and its overexpression did not cause evident abnormality. Together, we propose that Caspase activation may be an important trigger for
human Tau mediated pathogenic mechanism.
430A
Glia-Mediated Neurodegeneration in the
Drosophila melanogaster
CNS.
Ivan J. Santiago
1
, Israel C. Nnah
1
, Amandeep Kaur
1
, Rosa Mino
3
, Tadmiri R.
Venkatesh
1,2
. 1) Biology, The City College of New York, New York, NY; 2) The Graduate Center of the City University of New York, New York, NY; 3)
The University of North Carolina, Chapel Hill, NC.
Proper development, function and maintenance of the central nervous system (CNS) are reliant on the intricate interactions between glia and neurons. Glia
cells perform a variety of key functions such as maintaining homeostasis, trophic support and the uptake and recycling of neuronal debris. Disruptions in
glial function have been implicated in many neurological disorders. Despite their obvious importance in the CNS, glia remain much less characterized than
their neuronal counterparts. Drosophila glia have been classified into distinct subtypes based on their position and morphology. We have examined the role
of glia subsets in neuro-protection and neurodegeneration. Our studies show that glia specific expression of Drosophila-Cdh1(Rap/Fzr), a conserved
regulatory subunit of the Anaphase Promoting Complex/Cyclosome (APC/C), an E3 ubiquitin ligase, results in the loss of glia in the CNS at the 3rd instar
developmental stage. These larvae emerge into adult flies lacking subsets of glia and exhibit temperature-sensitive paralysis, age dependent