Multimodal mechanisms of human centriole engagement and disengagement.

Centrioles are unique cellular structures that replicate to produce identical copies, ensuring accurate chromosome segregation during mitosis. A new centriole, the "daughter", is assembled adjacent to an existing "mother" centriole. Only after the daughter centriole is fully developed as a complete replica, does it disengage and become the core of a new functional centrosome. The mechanisms preventing precocious disengagement of the immature daughter centriole have remained unclear. Here, we identify three key mechanisms maintaining mother-daughter centriole engagement: the cartwheel, the torus, and the pericentriolar material (PCM). Among these, the torus critically establishes the characteristic orthogonal engagement. We also demonstrate that engagement mediated by the cartwheel and torus is progressively released during centriole maturation. This release involves structural changes in the daughter, known as centriole blooming and distancing, respectively. Disrupting these structural transitions blocks subsequent steps, preventing centriole disengagement and centrosome conversion in the G1 phase. This study provides a comprehensive understanding of how the maturing daughter centriole progressively disengages from its mother through multiple steps, ensuring its complete structure and conversion into an independent centrosome.