Ral GTPases in Schwann cells promote radial axonal sorting in the peripheral nervous system

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Small GTPases, including Rho and Ras families, regulate Schwann cell biology.
• RalA and RalB GTPases function downstream of Ras in tumors, but their physiological roles in Schwann cells are unclear.

Purpose of the Study:

• To investigate the physiological role of Ral GTPases in Schwann cell development and function.

Main Methods:

• Utilized transgenic mice lacking one or both Ral genes (RalA and RalB).
• Examined peripheral nerve development and Schwann cell biology in vivo and ex vivo.
• Assessed axonal radial sorting, Schwann cell process formation, and lamellipodia dynamics.

Main Results:

• Ablation of a single Ral gene had no significant impact on early peripheral nerve development.
• Complete ablation of RalA and RalB resulted in persistent axonal radial sorting defects.
• Ral-deficient Schwann cells exhibited impaired process extension and lamellipodia formation.
• RalA was found to contribute to Schwann cell process extension via the exocyst complex.

Conclusions:

• Ral GTPases are critical for axonal radial sorting in peripheral nerves.
• Ral proteins are essential for Schwann cell process formation and maintenance.
• The exocyst complex mediates Ral GTPase function in Schwann cell development.