axon guidance

Definition

Target type: biologicalprocess

The chemotaxis process that directs the migration of an axon growth cone to a specific target site in response to a combination of attractive and repulsive cues. [ISBN:0878932437]

Axon guidance is the intricate process by which growing axons navigate through the developing nervous system to reach their appropriate target cells. This precise process is crucial for establishing functional neural circuits and ensuring proper brain development. Here's a detailed description of the key steps involved:

1. **Axon Initiation and Growth:** The process begins with the formation of a growth cone, a dynamic structure at the tip of the axon. The growth cone is highly sensitive to its environment and plays a critical role in sensing and responding to guidance cues.

2. **Guidance Cues:** Axon guidance is driven by a diverse array of molecular cues present in the extracellular matrix, neighboring cells, and target cells. These cues can be classified as attractive or repulsive, directing the axon toward or away from specific destinations.

* **Attractive Cues:** Netrins, Slit proteins, and some members of the semaphorin family are examples of attractive cues that promote axonal growth toward specific targets.

* **Repulsive Cues:** Other semaphorins, ephrins, and members of the Wnt family act as repulsive cues, guiding axons away from certain pathways.

3. **Signal Transduction:** The growth cone's receptors bind to guidance cues, initiating intracellular signaling pathways that ultimately control the axon's growth and direction. These pathways involve a complex interplay of proteins, including kinases, phosphatases, and cytoskeletal regulators.

4. **Cytoskeletal Dynamics:** Signal transduction pathways influence the organization and dynamics of the cytoskeleton within the growth cone. Actin filaments and microtubules provide the structural basis for growth cone extension, turning, and retraction.

* **Actin Filaments:** Actin polymerization and depolymerization drive the extension and retraction of filopodia, finger-like projections that explore the environment.

* **Microtubules:** Microtubules are involved in maintaining axon structure and facilitating long-range transport of organelles and signaling molecules.

5. **Target Recognition and Synapse Formation:** Once an axon reaches its target, it forms a synapse, a specialized junction where communication with the target cell occurs. The process of target recognition involves a variety of molecular interactions and often involves the exchange of electrical or chemical signals.

6. **Fine-Tuning and Refinement:** Axon guidance is a dynamic and adaptable process. After initial target selection, axons can undergo further refinement and adjustments to ensure precise connectivity. This involves processes such as axonal pruning, where unnecessary or inappropriate connections are eliminated.

7. **Disruption of Axon Guidance:** Errors in axon guidance can lead to developmental disorders affecting sensory, motor, and cognitive functions. These disorders can manifest as a range of neurological conditions, highlighting the critical importance of this process.'
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Proteins (36)

Compounds (566)