Hallmark cellular pathology of Alzheimer’s disease induced by mutant human tau expression in cultured Aplysia neurons
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The mechanisms underlying neurodegenerative diseases are the outcome of pathological alterations of evolutionary conserved molecular and cellular cascades. For this reason, Drosophila and C. elegans serve as useful model systems to study various aspects of neurodegenerative diseases. Here, we introduce the advantageous use of cultured Aplysia neurons (which express over 100 disease-related gene homologs shared with mammals), as a platform to study cell biological processes underlying the generation of tauopathy. Using live confocal imaging to follow cytoskeletal elements, autophagosomes, lysosomes, anterogradely and retrogradely transported organelles, complemented with electron microscopy, we demonstrate that the expression of mutant human tau in cultured Aplysia neurons leads to the development of hallmark Alzheimer disease (AD) pathologies. These include a reduction in the number of microtubules and their redistribution, impaired organelle transport, a dramatic accumulation of macro-autophagosomes and lysosomes, compromised neurite morphology and degeneration. Our study demonstrates the accessibility of the platform for long-term live imaging and quantification of subcellular pathological cascades leading to tauopathy. Based on the present study, it is conceivable that this system can also be used to screen for reagents that alter the pathological cascades.
KeywordsAutophagosomes Lysosomes Tauopathy Alzheimer’s disease Axoplasmic transport Aplysia
This study was supported by Grant No. 137/08 from the Israel Science Foundation (ISF), and Grant No. 300000-4955 from the Israel Ministry of Health. Parts of this work were conducted at the Charles E. Smith Family and Prof. Elkes Laboratory for Collaborative Research in Psychobiology. We thank Dr. E. Shapira, A. Dormann and H. Glickstein for technical help in preparing mRNAs, and complementary electron micrographs. The LC3-GFP construct was kindly given to us by Prof. Zvulun Elazar (Weizmann Institute). M.E. Spira is Levi DeViali Professor of Neurobiology.
Movie S1. Control neuron- uniform MT polar orientation and retrograde transport. The movie relates to Fig. 1. (Upper panel, green) EB3-GFP comet tails in a control axon, 100-200µm away from cell body, 72 h following mRNA microinjection. (Lower panel, red) retrograde transport of SR101 labeled vesicles along the same location of the same axon. The video is composed of 30 images, taken at intervals of 5.7 seconds. The frames are shown at a rate of 7/s. Scale bar: 10 µm. (MPEG 21537 kb)
Movie S4. Lysotracker and LC3-GFP labeled organelles in a control neuron. The movie relates to Fig. 6. (Upper panel, green) LC3-GFP labeled organelles along a 150µm segment extending from the axon hillock to the axon, 120 h after culturing. (Middle panel, red) lysotracker labeled organelles . (Lower panel) a merged image, created by overlaying the upper and middle panel. The video contains 25 images, taken at intervals of 7.8 seconds. The frames are shown at a rate of 7/s. Scale bar: 10 µm. (MPEG 31143 kb)
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