Axon growth and guidance

Question 1

Comer, J.D., Alvarez, S., Butler, S.J. et al. Commissural axon guidance in the developing spinal cord: from Cajal to the present day. Neural Dev 14, 9 (2019). https://doi.org/10.1186/s13064-019-0133-1

Answer 1

• Specialised populations of cells allow developing molecules to form a pathway to the appropriate synaptic partner via guidance molecules
• Floor of the CNS is important in neuronal development for extension of commisural axons across the ventral midline
• Growth cones integrate long range chemoattractants or chemoreppellants to orient growth from a distance. There are also contact mediated chemoattractants or chemorepellants that orient axons through direct contact
• Netrin and slit families are important

Question 2

Axon growth https://doi-org.iclibezp1.cc.ic.ac.uk/10.1002/dneu.22780

Answer 2

• Axon guiding, branching, formation and consolidation of synaptic contacts in specific target areas
• Neurons and non-neuronal cells such as astrocytes and microglia actively participate in synapse formation and remodeling.
• Spatial and temporal dynamics of gene expression
• Transcription factors unmask chromatin domains during development to start cellular programmes
• Following trauma, there is difficulty

Question 3

What does axon growth depend on?

Answer 3

• Extracellular guidance cues
• Growth cone
• Intracellular signalling
• Cytoskeletal rearrangements
• CHanges in transcription

Question 4

List synaptogenic factors

Answer 4

• WNT family (stimulate presynaptic differentiation by modulating microtubule dynamics at the growth cone)
• Neurexin/neuroligin (target cells expressing cell surface receptor, important in stimulating pre synaptic stimulation)