axon target recognition

Definition

Target type: biologicalprocess

The process in which an axon recognizes and binds to a set of cells with which it may form stable connections. [ISBN:0878932437]

Axon target recognition is a crucial step in neuronal development, enabling neurons to establish precise connections with their appropriate targets. This intricate process involves a series of molecular interactions that guide the growing axon to its designated destination. The process begins with the initiation of axon outgrowth from the neuronal cell body, driven by intrinsic factors and external cues. As the axon extends, it navigates through the developing nervous system, relying on a complex interplay of attractive and repulsive guidance cues. These cues can be secreted proteins, cell surface molecules, or extracellular matrix components, each acting as a signal to guide the axon towards or away from specific pathways. Several families of guidance molecules play critical roles in target recognition, including:

* Netrins: These secreted proteins act as chemoattractants, guiding axons towards their target regions.
* Slits: These repulsive cues guide axons away from specific pathways.
* Ephrins and Eph receptors: These transmembrane proteins mediate both attractive and repulsive interactions, influencing axon pathfinding and target selection.
* Semaphorins: These secreted or membrane-bound proteins act as both attractive and repulsive cues, depending on the specific semaphorin and receptor involved.

These guidance molecules interact with receptors on the axon surface, triggering intracellular signaling pathways that ultimately regulate axon growth, turning, and branching. These pathways involve a complex network of proteins, including GTPases, kinases, and transcription factors.

The specificity of target recognition arises from the coordinated expression of guidance cues and receptors in both the axon and its target. This precise matching ensures that axons connect with their appropriate targets, forming functional neuronal circuits.

In addition to the guidance cues, other factors influence axon target recognition, including:

* Activity-dependent mechanisms: Neural activity can modify axon targeting by influencing the expression of guidance cues and receptors.
* Cell-cell interactions: Axons can directly interact with their target cells through cell adhesion molecules, contributing to the formation of stable connections.
* Mechanical forces: Tension forces exerted on the growing axon can influence its trajectory and target recognition.

The interplay of these factors ensures that axons reach their appropriate targets, establishing the intricate network of connections that underlie brain function. Defects in axon target recognition can disrupt these connections, leading to developmental disorders and neurological diseases.
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