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Published August 21, 2007 | Published + Supplemental Material
Journal Article Open

One at a time, live tracking of NGF axonal transport using quantum dots


Retrograde axonal transport of nerve growth factor (NGF) signals is critical for the survival, differentiation, and maintenance of peripheral sympathetic and sensory neurons and basal forebrain cholinergic neurons. However, the mechanisms by which the NGF signal is propagated from the axon terminal to the cell body are yet to be fully elucidated. To gain insight into the mechanisms, we used quantum dot-labeled NGF (QD-NGF) to track the movement of NGF in real time in compartmentalized culture of rat dorsal root ganglion (DRG) neurons. Our studies showed that active transport of NGF within the axons was characterized by rapid, unidirectional movements interrupted by frequent pauses. Almost all movements were retrograde, but short-distance anterograde movements were occasionally observed. Surprisingly, quantitative analysis at the single molecule level demonstrated that the majority of NGF-containing endosomes contained only a single NGF dimer. Electron microscopic analysis of axonal vesicles carrying QD-NGF confirmed this finding. The majority of QD-NGF was found to localize in vesicles 50–150 nm in diameter with a single lumen and no visible intralumenal membranous components. Our findings point to the possibility that a single NGF dimer is sufficient to sustain signaling during retrograde axonal transport to the cell body.

Additional Information

© 2007 National Academy of Sciences of the USA. Contributed by Steven Chu, July 6, 2007 (received for review March 19, 2007). Published online on August 14, 2007, 10.1073/pnas.0706192104. B.C. thanks Drs. Harold Kim, Janice S. Valletta, Keith Weninger, and Wei-Hau Chang for their generous assistance for her research. E.L.B. thanks Jean Edens at Caltech for her skill with thin-sectioning for electron microscopy. This work was supported by National Science Grants PHY-0420752 and PHY-0647161, National Aeronautics and Space Administration Grant NNC04GB49G, National Institutes of Health (NIH) Grants NS24054, NS38869, AG16999, NS046810, NS05537, and GM47368, The Larry L. Hillblom Foundation, The Deane Johnson Fund, The Adler Foundation, Dart Neurosciences LLP, and The Moore Foundation. B.C. acknowledges support from the Pathway to Independence Career Award from NIH. Author contributions: B.C. and C.W. contributed equally to this work; B.C., C.W., W.C.M., and S.C. designed research; B.C., C.W., L.C., A.R., E.L.B., and W.-P.L. performed research; B.C. contributed new reagents/analytic tools; B.C. analyzed data; and B.C., C.W., and W.C.M. wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/cgi/content/full/0706192104/DC1.

Attached Files

Published - CUIpnas07.pdf

Supplemental Material - CUIpnas07matmeth.pdf

Supplemental Material - CUIpnas07movie1.avi

Supplemental Material - CUIpnas07movie2.avi

Supplemental Material - CUIpnas07movie3.avi

Supplemental Material - CUIpnas07movie4.avi

Supplemental Material - CUIpnas07movie5.avi

Supplemental Material - CUIpnas07suppfig6.pdf

Supplemental Material - CUIpnas07suppfig7.pdf

Supplemental Material - CUIpnas07suppfig8.pdf


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August 22, 2023
October 16, 2023