Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
XB-ART-47684
Neural Dev December 1, 2013; 8 22.

Growth cone-specific functions of XMAP215 in restricting microtubule dynamics and promoting axonal outgrowth.

Lowery LA , Stout A , Faris AE , Ding L , Baird MA , Davidson MW , Danuser G , Van Vactor D .


Abstract
BACKGROUND: Microtubule (MT) regulators play essential roles in multiple aspects of neural development. In vitro reconstitution assays have established that the XMAP215/Dis1/TOG family of MT regulators function as MT ''plus-end-tracking proteins'' (+TIPs) that act as processive polymerases to drive MT growth in all eukaryotes, but few studies have examined their functions in vivo. In this study, we use quantitative analysis of high-resolution live imaging to examine the function of XMAP215 in embryonic Xenopus laevis neurons. RESULTS: Here, we show that XMAP215 is required for persistent axon outgrowth in vivo and ex vivo by preventing actomyosin-mediated axon retraction. Moreover, we discover that the effect of XMAP215 function on MT behavior depends on cell type and context. While partial knockdown leads to slower MT plus-end velocities in most cell types, it results in a surprising increase in MT plus-end velocities selective to growth cones. We investigate this further by using MT speckle microscopy to determine that differences in overall MT translocation are a major contributor of the velocity change within the growth cone. We also find that growth cone MT trajectories in the XMAP215 knockdown (KD) lack the constrained co-linearity that normally results from MT-F-actin interactions. CONCLUSIONS: Collectively, our findings reveal unexpected functions for XMAP215 in axon outgrowth and growth cone MT dynamics. Not only does XMAP215 balance actomyosin-mediated axon retraction, but it also affects growth cone MT translocation rates and MT trajectory colinearity, all of which depend on regulated linkages to F-actin. Thus, our analysis suggests that XMAP215 functions as more than a simple MT polymerase, and that in both axon and growth cone, XMAP215 contributes to the coupling between MTs and F-actin. This indicates that the function and regulation of XMAP215 may be significantly more complicated than previously appreciated, and points to the importance of future investigations of XMAP215 function during MT and F-actin interactions.

PubMed ID: 24289819
PMC ID: PMC3907036
Article link: Neural Dev
Grant support: [+]
Genes referenced: actl6a ckap5 gnl3 mapre1
Morpholinos: ckap5 MO1 ckap5 MO2


Article Images: [+] show captions
References [+] :
Ahmad, Motor proteins regulate force interactions between microtubules and microfilaments in the axon. 2000, Pubmed


Xenbase: The Xenopus Model Organism Knowledgebase.
Version: 4.15.0
Major funding for Xenbase is provided by grant P41 HD064556