Stable centrosomal roots disentangle to allow interphase centriole independence

Area of Science:

• Cell Biology
• Organelle Biology
• Biophysics

Background:

• The centrosome, a non-membrane-bound organelle, comprises two centrioles within pericentriolar material (PCM).
• Centrosome cohesion, the stable association of centrioles, is crucial but poorly understood due to the absence of a lipid membrane.
• Rootletin protein is hypothesized to form fibers linking centrioles, yet their properties remain largely unknown.

Purpose of the Study:

• To investigate the structure, assembly, and dynamics of rootletin fibers responsible for centrosome cohesion.
• To elucidate the mechanism by which centrioles maintain physical association within the centrosome.
• To understand the role of rootletin in organizing interphase centrosomes.

Main Methods:

• Live-cell imaging of endogenously tagged rootletin.
• Cell fusion experiments to study centrosome cohesion dynamics.
• Analysis of rootletin fiber formation and centriole association.

Main Results:

• Rootletin forms large, stable, bifurcating fibers that assemble slowly over hours on mature centrioles.
• Nascent centrioles require polo-like kinase 1 (PLK1) activity to initiate rootletin fiber formation.
• Centrioles can organize as independent units, with transient root separation during repositioning and independent reshuffling observed in induced duplicate pairs.

Conclusions:

• Progressively nucleated polymers, specifically rootletin fibers, mediate the dynamic association of centrioles.
• These findings reveal plasticity in centrosome cohesion, explaining how 1 or 2 interphase centrosomes are organized.
• The study provides insights into the self-organization principles of non-membrane-bound organelles.