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Axonal guidance in the chicken retina
1Naturwissenschaftliches und Medizinisches Institut, Universität Tübingen, Reutlingen, Germany.
Development (Cambridge, England)
|May 1, 1995
Summary
Retinal axon guidance relies on radial glia, which provide permissive cues in the inner retina and inhibitory signals in outer layers, ensuring proper neural circuit formation.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- During retina development, ganglion cell axons navigate exclusively to the innermost layer, avoiding outer retinal tissues.
- Understanding the molecular and cellular mechanisms guiding this precise axonal pathfinding is crucial for comprehending neural circuit formation.
Purpose of the Study:
- To elucidate the guidance mechanisms directing retinal ganglion cell axons during development.
- To investigate the roles of stereotropism, basal lamina interactions, axonal fasciculation, and radial glia in axon pathfinding.
Main Methods:
- Explants of embryonic chicken retinae were cultured on retinal cryosections (cryoculture).
- Investigated axon growth on cryosections with manipulated radial glia, physical barriers, and UV-inactivated proteins.
- Assessed axon outgrowth on purified glial endfeet and outer retina cells.
Main Results:
- Ganglion cell axons preferentially grew on the innermost retina layer and avoided outer layers, mimicking in vivo growth.
- Stereotropism, laminin, and axonal fasciculation were excluded as primary guidance cues.
- Radial glial endfeet were essential for oriented axonal elongation along the inner retina; their elimination disrupted guidance.
- Outer retina layers exhibited inhibitory components, while glial endfeet provided a permissive growth substratum.
Conclusions:
- Retinal axon guidance involves a dual mechanism: permissive cues from radial glia in the inner retina and inhibitory components in the outer retina.
- Radial glia play an instructive role in directing ganglion cell axons to their correct targets.