Identification of maxillary factor, a maxillary process-derived chemoattractant for developing trigeminal sensory...

Area of Science:

• Neuroscience
• Developmental Biology
• Molecular Biology

Background:

• Trigeminal sensory axons innervate maxillary and mandibular processes.
• Previous research identified a chemoattractant, Maxillary Factor, from these processes.
• The role of Maxillary Factor in axon guidance remains to be fully elucidated.

Purpose of the Study:

• To identify the components of Maxillary Factor.
• To investigate the role of these components in trigeminal axon guidance.
• To determine the contribution of neurotrophins to early axon trajectory.

Main Methods:

• Biochemical analysis to identify Maxillary Factor components.
• In vitro axon guidance assays.
• Analysis of trigeminal axon trajectories in genetically modified mice lacking specific neurotrophins.

Main Results:

• Maxillary Factor activity is attributed to neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF).
• Both NT-3 and BDNF are produced by target epithelia and pathway mesenchyme.
• Trigeminal axon trajectories are largely normal in mice deficient in both NT-3 and BDNF, suggesting alternative guidance mechanisms.

Conclusions:

• NT-3 and BDNF are unlikely to provide directional cues for initial trigeminal axon growth.
• These neurotrophins may play a trophic role rather than a guidance role in early development.
• Other guidance cues are sufficient for the initial stages of trigeminal axon pathfinding.