Emerging evidence for cell-autonomous axon guidance.

Area of Science:

• Neuroscience
• Developmental Biology
• Cell Biology

Background:

• Axon guidance in the central nervous system (CNS) relies on environmental cues.
• Retinal ganglion cells (RGCs) navigate to targets using molecular signals.

Purpose of the Study:

• To elucidate the novel self-guiding mechanism of RGC axon pathfinding.
• To investigate the role of RGMb, VLK, and LRP5 in Wnt3a signaling and axon guidance.

Main Methods:

• Investigated the interaction between RGMb, VLK, and LRP5.
• Analyzed the effect of RGMb phosphorylation on LRP5 localization.
• Examined Wnt3a signaling modulation along the retinal dorso-ventral axis.

Main Results:

• RGMb down-regulates Wnt3a signaling by reducing cell-surface LRP5.
• Extracellular tyrosine kinase VLK phosphorylates RGMb, leading to LRP5 internalization.
• A dorsal-high VLK gradient creates a ventral-high LRP5 gradient, guiding RGC axon growth.

Conclusions:

• Extracellular phosphorylation of RGMb is a novel self-guiding mechanism for RGC axons.
• This pathway establishes Wnt-signal gradients for retino-tectal map formation, independent of target-derived signals.