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Axon fasciculation and differences in midline kinetics between pioneer and follower axons within commissural fascicles

Bak-Maier, Magdalena and Fraser, Scott E. (2003) Axon fasciculation and differences in midline kinetics between pioneer and follower axons within commissural fascicles. Development, 130 (20). pp. 4999-5008. ISSN 0950-1991. http://resolver.caltech.edu/CaltechAUTHORS:BAKdev03

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[img] Video (QuickTime) (Movie 1 - Timelapse movie showing how axons establish the POC) - Supplemental Material
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[img] Video (QuickTime) (Movie 2 - Timelapse movie showing axons growing and establishing the POC commissure) - Supplemental Material
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[img] Video (QuickTime) (Movie 3 - Timelapse movie showing another POC tract being established) - Supplemental Material
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Abstract

Early neuronal scaffold development studies suggest that initial neurons and their axons serve as guides for later neurons and their processes. Although this arrangement might aid axon navigation, the specific consequence(s) of such interactions are unknown in vivo. We follow forebrain commissure formation in living zebrafish embryos using timelapse fluorescence microscopy to examine quantitatively commissural axon kinetics at the midline: a place where axon interactions might be important. Although it is commonly accepted that commissural axons slow down at the midline, our data show this is only true for leader axons. Follower axons do not show this behavior. However, when the leading axon is ablated, follower axons change their midline kinetics and behave as leaders. Similarly, contralateral leader axons change their midline kinetics when they grow along the opposite leading axon across the midline. These data suggest a simple model where the level of growth cone exposure to midline cues and presence of other axons as a substrate shape the midline kinetics of commissural axons.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1242/10.1242/dev.00713DOIUNSPECIFIED
http://dev.biologists.org/cgi/content/abstract/130/20/4999PublisherUNSPECIFIED
Additional Information:Copyright © 2003 The Company of Biologists Limited. Accepted 1 July 2003. We thank Andres Collazo and Olivier Bricaud for suggesting the gata2::GFP line as candidate for our work as well as Shuo Lin for the gata2::GFP adults. We thank Kai Zinn, Reinhard Köster, Cyrus Papan and Helen McBride for discussions and critical reading of the manuscript. This work was supported by NIH RO1 HD043897. Movies available online. Movie 1 - Timelapse movie showing how axons establish the POC. Time interval between each frame is 3 minutes. Movie 2 - Timelapse movie showing axons growing and establishing the POC commissure. The initial axon projecting towards the midline was injured immediately before crossing it by heat. Over the next few frames, blebbing caused by heat can be seen as the axon deteriorates. Later, follower axons can be seen in subsequent frames of the movie. Only the first follower axon slows down in the midline domain following the injury of the original leader axon. The commissure eventually forms correctly. Movie 3 - Timelapse movie showing another POC tract being established. Initially, two growth cones, one from each of the vrc, project toward the midline with one crossing the midline region first. Although, initially, both growth cones have complex morphologies, upon contacting each other they change shape and become elongated, even though the second growth cone has not yet crossed the midline. Midline kinetics of the second axon are similar to later follower axons.
Funders:
Funding AgencyGrant Number
National Institutes of HealthRO1 HD043897
Subject Keywords:Forebrain, Zebrafish, Commissural axon, Neuronal scaffold, Growth cone, Intermediate target, Growth cone morphology, Growth cone behavior, GATA2, Axon pathway
Record Number:CaltechAUTHORS:BAKdev03
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:BAKdev03
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11889
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:08 Oct 2008 23:01
Last Modified:26 Dec 2012 10:23

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