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The influence of activity on axon pathfinding in the optic tectum
Author(s) -
Kita Elizabeth M.,
Scott Ethan K.,
Goodhill Geoffrey J.
Publication year - 2015
Publication title -
developmental neurobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.716
H-Index - 129
eISSN - 1932-846X
pISSN - 1932-8451
DOI - 10.1002/dneu.22262
Subject(s) - pathfinding , axon guidance , neuroscience , biology , tectum , zebrafish , axon , growth cone , anatomy , midbrain , central nervous system , computer science , genetics , theoretical computer science , shortest path problem , gene , graph
The relative importance of neural activity versus activity‐independent cues in shaping the initial wiring of the brain is still largely an open question. While activity is clearly critical for circuit rearrangements after initial connections have been made, whether it also plays a role in initial axon pathfinding remains to be determined. Here, we investigated this question using the guidance of zebrafish retinal ganglion cell axons to their targets in the tectum as a model. Recent results have implicated biased branching as a key feature of pathfinding in the zebrafish tectum. Using tetrodotoxin to silence neural activity globally, we found a decrease in the area covered by axon branches during pathfinding. After reaching the target, there were dynamic differences in axon length, area and the number of branches between conditions. However, other aspects of pathfinding were unaffected by silencing, including the ratio of branches directed toward the target, length, and number of branches, as well as turning angle, velocity, and number of growth cones per axon. These results challenge the hypothesis that neural connections develop in sequential stages of molecularly guided pathfinding and activity‐based refinement. Despite a maintenance of overall guidance, axon pathfinding dynamics can nevertheless be altered by activity loss. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 75: 608–620, 2015