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Orienting axon growth: spinal nerve segmentation and surround-repulsion.
D Tannahill1, J M Britto, M M Vermeren
1Department of Anatomy, University of Cambridge, United Kingdom. dt10003@mole.bio.cam.ac.uk
The International Journal of Developmental Biology
|April 13, 2000
Summary
Spinal axon pathfinding in vertebrate embryos relies on both contact and chemical repulsion. Surround-repulsion mechanisms guide motor and sensory axons through somites, crucial for neural development.
Area of Science:
- Developmental Biology
- Neuroscience
- Embryology
Background:
- Spinal nerve development involves complex axon pathfinding.
- Somites exhibit antero-posterior polarity influencing neural growth.
Purpose of the Study:
- To investigate the guidance mechanisms determining spinal axon trajectories in vertebrate embryos.
- To elucidate the roles of contact repulsion and chemorepulsion in somite navigation.
Main Methods:
- Analysis of spinal nerve trajectories in higher vertebrate embryos.
- Review of molecular candidates for contact repellents.
- Investigation of diffusible repellents from embryonic structures.
Main Results:
- Axon orientation is governed by simultaneous contact repulsion and chemorepulsion.
- Motor and sensory axons are repelled from the posterior half of somites.
- Diffusible repellents from the notochord and dermamyotome guide sensory axon trajectories dorsally.
Conclusions:
- Repulsion by surrounding tissues ('surround-repulsion') is a primary force in 3D axon growth.
- Distinct repulsive cues dictate both antero-posterior and dorsoventral navigation.
- Understanding these mechanisms is key to comprehending neural development.