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Updated: Nov 21, 2025
High-resolution Live Imaging of Cell Behavior in the Developing Neuroepithelium
Published on: April 12, 2012
Axon guidance at the spinal cord midline-A live imaging perspective
Alexandre Dumoulin1,2, Nikole R Zuñiga1,2, Esther T Stoeckli1,2
1Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
Abstract:
During neural circuit formation, axons navigate several choice points to reach their final target. At each one of these intermediate targets, growth cones need to switch responsiveness from attraction to repulsion in order to move on. Molecular mechanisms that allow for the precise timing of surface expression of a new set of receptors that support the switch in responsiveness are difficult to study in vivo. Mostly, mechanisms are inferred from the observation of snapshots of many different growth cones analyzed in different preparations of tissue harvested at distinct time points. However, to really understand the behavior of growth cones at choice points, a single growth cone should be followed arriving at and leaving the intermediate target. Existing ex vivo preparations, like cultures of an "open-book" preparation of the spinal cord have been successfully used to study floor plate entry and exit, but artifacts prevent the analysis of growth cone behavior at the floor plate exit site. Here, we describe a novel spinal cord preparation that allows for live imaging of individual axons during navigation in their intact environment. When comparing growth cone behavior in our ex vivo system with snapshots from in vivo navigation, we do not see any differences. The possibility to observe the dynamics of single growth cones navigating their intermediate target allows for measuring growth speed, changes in morphology, or aberrant behavior, like stalling and wrong turning. Moreover, observation of the intermediate target-the floor plate-revealed its active participation and interaction with commissural axons during midline crossing.
Insights
Researchers developed a novel ex vivo spinal cord preparation for live imaging of individual axons navigating choice points. This method allows detailed observation of growth cone dynamics, revealing interactions at intermediate targets like the floor plate.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Axon guidance during neural circuit formation involves growth cones switching responsiveness at intermediate targets.
- Studying the molecular mechanisms of these responsiveness switches in vivo is challenging due to limitations in observing dynamic growth cone behavior.
- Existing ex vivo preparations have artifacts that hinder analysis of growth cone exit from sites like the floor plate.
Purpose of the Study:
- To develop and validate a novel ex vivo spinal cord preparation for live imaging of individual axons.
- To enable real-time observation of growth cone dynamics at intermediate targets, specifically the floor plate.
- To compare growth cone behavior in the novel ex vivo system with in vivo observations.
Main Methods:
- Development of a novel ex vivo spinal cord preparation allowing live imaging of axon navigation.
- Live imaging of individual axons and their growth cones within the intact ex vivo environment.
- Comparative analysis of growth cone behavior in the ex vivo system versus in vivo snapshots.
Main Results:
- The novel ex vivo preparation successfully allows live imaging of individual axons navigating their environment.
- Growth cone behavior observed in the ex vivo system closely matches in vivo snapshots, validating the model.
- The system enables measurement of growth speed, morphological changes, and aberrant behaviors (stalling, turning).
- The floor plate was observed to actively interact with commissural axons during midline crossing.
Conclusions:
- The novel ex vivo spinal cord preparation provides an unprecedented tool for studying dynamic growth cone behavior at choice points.
- This system overcomes limitations of previous methods, allowing detailed analysis of axon navigation and intermediate target interactions.
- The findings support the active role of intermediate targets, like the floor plate, in guiding axon pathfinding.
