A helical inner scaffold provides a structural basis for centriole cohesion.

Area of Science:

• Cell Biology
• Structural Biology
• Microscopy

Background:

• Centrioles possess a unique ninefold radial arrangement of microtubule triplets (MTTs).
• Centriole structural integrity is vital for centrosome and cilia function, yet the underlying mechanisms remain unclear.
• MTT cohesion is critical for resisting forces during ciliary beating and mitotic spindle activity.

Purpose of the Study:

• To investigate the structural basis of centriole cohesion.
• To identify the molecular components responsible for maintaining centriole integrity.

Main Methods:

• Cryo-electron tomography and subtomogram averaging of centrioles from four species.
• Ultrastructure Expansion Microscopy (U-ExM).

Main Results:

• A helical inner scaffold, spanning ~70% of centriole length, was identified binding MTTs.
• Four proteins (POC5, POC1B, FAM161A, Centrin-2) localize to this scaffold.
• These proteins form a complex that directly binds microtubules, explaining MTT cohesion.

Conclusions:

• The study reveals a structural and molecular basis for centriole cohesion and geometry.
• The identified scaffold and protein complex are crucial for maintaining centriole structural integrity.
• This finding advances our understanding of centrosome and cilia biogenesis.