Nanometer-Resolution Characterization of Axonal Transport
Defects in a Drosophila Model of Alzheimer’s Disease
Ge Yang1,2,3
1Department
of Biomedical Engineering
2Lane Center for Computational Biology
3Department of Biological Sciences
Carnegie Mellon University
Pittsburgh Fly Meeting, July 29, 2011
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From Brain Facts, Society for Neuroscience
An Overview of Axonal Transport
Hirokawa N., JCB, 94:129, 1982
Bars: 0.1m
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Axonal transport is critical to survival and function of neurons.
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Transport defects have been implicated in many neurodegenerative diseases.
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Axonal transport is a powerful model of intracellular transport.
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Molecular Machinery of Axonal Transport
Adapted from Schliwa &
Woehlke, Nature, 422:759,
2003
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Potential Mechanisms of Axonal Transport Defects
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Microtubule Associated Protein Tau in Axonal Transport
Ballatore et al, Nat. Rev. Neurosci. 2007
Morris et al, Neuron, 2011
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Kinesin and Dynein Compete and Coordinate
Exclusive Presence
Tug-of-War
Coordinated Activation
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How does tau modulate axonal transport?
[tau]
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A Drosophila Model of Alzheimer’s Disease
• Two pathological hallmarks of AD: Aβ plaques & tau tangles
• Control:
SG26.1 GAL4/+; UAS-APPYFP/+  transport is driven by kinesin-1
SG26.1 GAL4/+; UAS-SynGFP
 transport is driven by kinesin-3
• Mutants:
SG26.1 GAL4/+; UAS-APPYFP/+; UAS-wt hTau/+
SG26.1 GAL4/+; UAS-APPYFP/+; UAS-R406W hTau/+
Wittmann et al, Science, 2001
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Imaging Axonal Transport
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Tau Overexpression Affects Axonal Transport
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Nanometer Resolution Cargo Detection
(2, 2)
(2, 2)
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Detection Resolution Validation
Q-dots
F-beads
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Cargo Population Analysis
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Cargo Velocity & Switching Frequency
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Pause Frequency & Duration
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Axon Swelling & Accumulation of APP Vesicles
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Axon Swelling & Accumulation of SYNT Vesicles
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Velocity Mode Analysis & Comparison
anterograde
retrograde
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Summary
• Tau modulates axonal cargo transport through affecting kinesin driven
cargo movement.
• Dynein mediated cargo movement is indirectly affected through the
interaction between kinesin and dynein.
• Tau overexpression induces axon swelling and cargo aggregation.
• Regional variation of axonal transport is consistent with a spatial
gradient of tau.
• Axonal transport defects started to develop in the early stage of fly
development.
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Acknowledgement
Minhua Qiu
Khyti Dave
Jacob Heng-Kai Sheu
Breanna Stillo
Yiyi Yu
Jonathan Minden (CMU)
Brooke McCartney (CMU)
Larry Goldstein (UCSD & HHMI)
Shermali Gunawardena (University of Buffalo)
Mel Feany (Harvard Medical School)
Funding
National Science Foundation
Samuel & Emma Winters Foundation
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