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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An Overview of Axonal Transport

• Axonal transport is critical to survival and function of neurons.

• Transport defects have been implicated in many neurodegenerative

diseases.

• Axonal transport is a powerful model of intracellular transport.

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Bars: 0.1mHirokawa N., JCB, 94:129, 1982

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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. 2007Morris 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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[tau]

How does tau modulate axonal transport?

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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Q-dots F-beads

Detection Resolution Validation

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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anterograde retrograde

Velocity Mode Analysis & Comparison

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Summary

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• 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.

FundingNational Science FoundationSamuel & Emma Winters Foundation

Acknowledgement

Jonathan Minden (CMU)Brooke McCartney (CMU) Larry Goldstein (UCSD & HHMI)Shermali Gunawardena (University of Buffalo)Mel Feany (Harvard Medical School)

Minhua QiuKhyti DaveJacob Heng-Kai SheuBreanna StilloYiyi Yu

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