Fig. 1. Centrosome biogenesis and the cell cycle in animal cells.

Schematic representation of the centrosome/centriole duplication cycle in animal cells. The centrosome consists of mother (green) and daughter centrioles (red), that are interconnected by S-M tethers and embedded in pericentriolar material (PCM), which anchors microtubules. The cycle can be separated in four slightly overlapping phases. i) Centriole disengagement, ii) centriole duplication, iii) centrosome maturation and iv) centrosome separation followed by spindle assembly. The mother centriole can be distinguished by the presence of appendages. During disengagement centrioles lose their orthogonal arrangement through the removal of the S-M linker. During S phase, procentrioles forms perpendicular to each mother centriole. During S-G2 phases, the daughter centrioles continue to elongate. In late S-phase G2, the centrosome increases in size and the newly formed centriole pairs disconnect through the disassembly of the G1-G2 tether, so that at the onset of G2/M the two centrosomes move to opposite sides of the cell and establish the two mitotic spindle poles. At the end of the cycle, the daughter centrioles acquire appendages and behave as a mother centriole during the subsequent cycle. When cell exit the cell cycle and enter G0, centrioles move to the plasma membrane (pm) and assemble cilia.