Wdr4 promotes cerebellar development and locomotion through Arhgap17-mediated Rac1 activation

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Mutations in WDR4, a CUL4 E3 ligase substrate adaptor, are linked to cerebellar atrophy and gait abnormalities.
• The precise molecular mechanisms underlying WDR4's role in cerebellar development are not well understood.

Purpose of the Study:

• To elucidate the function of Wdr4 in cerebellar development and identify the underlying molecular mechanisms.
• To investigate the impact of Wdr4 deficiency and disease-associated variants on cerebellar structure and function.

Main Methods:

• Utilized mouse models with Wdr4 deficiency in cerebellar granule neuron progenitors (GNPs).
• Analyzed cerebellar foliation, granular layer sizes, Purkinje neuron organization, and molecular layer development.
• Investigated the cell cycle regulation of GNPs and the role of Arhgap17 and Rac1.

Main Results:

• Wdr4 deficiency in GNPs led to reduced cerebellar foliation, smaller granular layers, disorganized Purkinje neurons, and impaired locomotion.
• Wdr4 was found to prevent premature cell cycle exit in GNPs by promoting ubiquitination and degradation of Arhgap17, thereby activating Rac1.
• Disease-associated WDR4 variants failed to maintain GNP cell cycle progression.

Conclusions:

• Wdr4 plays a critical, previously unrecognized role in cerebellar development and locomotion.
• Wdr4 regulates GNP proliferation via the Arhgap17-Rac1 pathway, essential for proper cerebellar formation.
• Understanding Wdr4's function offers insights into WDR4-related disorders like primordial dwarfism and Galloway-Mowat syndrome.