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Axon guidance (also called axon pathfinding) is a subfield of neural development concerning the process by which neurons send out axons to reach their correct targets. Axons often follow very precise paths in the nervous system, and how they manage to find their way so accurately is an area of ongoing research.
Semaphorins are a family of chemical signaling molecules involved in axonal targeting and guidance. Sema3 was the first vertebral Semaphorin discovered, [ 18 ] and since then Semaphorins have been shown to elicit both attraction and repulsive responses in commissural axons; additionally, Semaphorins can function as a secreted or contact ...
Growth cone receptors detect the presence of axon guidance molecules such as Netrin, Slit, Ephrins, and Semaphorins. It has more recently been shown that cell fate determinants such as Wnt or Shh can also act as guidance cues. The same guidance cue can act as an attractant or a repellent, depending on context.
An important family of adhesion molecules is constituted by the cadherins, whose different combination on targeting cells allow the traction and guidance of the forming axons. A typical example of layers with combinatorial expression of these molecules is the tectal laminae in the chick tectum, where the N-cadherin molecule is present only in ...
The vertebrate orthologue of UNC-6, netrin-1 was determined to be a key guidance cue for axons moving toward the ventral midline in the rodent embryo spinal cord. Netrin-1 has been identified as a critical component of embryonic development with functions in axon guidance, cell migration, morphogenesis and angiogenesis. The most recent studies ...
Guidance molecules act as cues by carrying information to receptive cells; administering this information which tells the cell and its entities how to properly align. [10] Slit proteins behave as such when working in axonal guidance during the development of the nervous system. Similarly, these proteins help to orchestrate the development of ...
For example, guidance molecules can initiate, extend, stabilize, or retract individual filopodia, as well as attract various adhesion molecules to impact their physical state. Some of the various chemotactic cues that have been explored in the mechanisms of pioneer axons include netrin , ephrin , semaphorin , Slit-Robo , and Notch .
Netrins are chemotropic; a growing axon will either move towards or away from a higher concentration of netrin. Though the detailed mechanism of axon guidance is not fully understood, it is known that netrin attraction is mediated through UNC-40/DCC cell surface receptors and repulsion is mediated through UNC-5 receptors.