Molecular architecture of the C. elegans centriole

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Organelle assembly is fundamental to life sciences.
• Centrioles are crucial organelles, and Caenorhabditis elegans has been vital for identifying conserved assembly components.
• Previous high-precision localization of centriole components in C. elegans was limited by the small size of the organelle.

Purpose of the Study:

• To decipher the molecular architecture of the C. elegans centriole with high spatial precision.
• To understand the underlying mechanisms of centriole assembly.

Main Methods:

• Ultrastructure Expansion coupled with STimulated Emission Depletion (U-Ex-STED) microscopy.
• Electron microscopy (EM) and electron tomography (ET).
• Registration of U-Ex-STED and EM data using the radial array of microtubules.

Main Results:

• Achieved an effective lateral resolution of approximately 14 nm.
• Localized 12 centriolar and PeriCentriolar Material (PCM) components with distinct ring-like distributions and 9-fold radial symmetry.
• Identified the assembly site of the procentriole and the sequential recruitment of key proteins (SAS-6, SAS-5, SAS-4, microtubules).
• Discovered an offset radial symmetry of SAS-6 and SAS-4 relative to microtubules, indicating a chiral centriole ensemble.
• Mapped proteins to specific ultrastructural compartments and identified a SAS-7-localizing region excluding ribosomes.

Conclusions:

• The study provides an unprecedentedly detailed molecular architecture of the C. elegans centriole.
• Establishes a comprehensive framework for understanding centriole biogenesis and function.
• Reveals novel insights into the chiral nature of centriole assembly and component organization.