Skip to main content
. 2014 Sep 5;369(1650):20130460. doi: 10.1098/rstb.2013.0460

Figure 1.

Figure 1.

Centriole assembly pathway in vertebrates. (a) Centrioles are cylindrical structures composed of nine microtubule triplets symmetrically arranged about a central core. The components important to the discussion here are indicated in the legend. Depicted is a longitudinal section of a mother centriole, which has two types of appendages, distal and subdistal, and lacks the internal cartwheel structure. The base of the mother centriole is embedded in the pericentriolar material. The formation of a procentriole has been initiated by assembly of the stalk and cartwheel from the side of the mother centriole. (a: 1–4) Stages of procentriole formation, depicted as viewed by cross section of centriole at X in longitudinal section. The mother centriole is not shown in (a: 2–4) for clarity, but is present and engaged to the procentriole throughout the process shown. (a-1) PLK4 accumulates at a single focus, in conjunction with CEP152 and CEP192, which are distributed in rings around the circumference of the centriole. PLK4 stimulates the assembly of a stalk and ninefold symmetric cartwheel that will provide structure to the procentriole and keep it engaged to the mother centriole. (a-2) Nine A-tubules are nucleated by the gamma-tubulin ring complex (gamma-TURC), in association with the cartwheel. These grow unidirectionally from the proximal to the distal end of the centriole. The A-tubules remain capped by the gamma-TURC throughout the assembly process, eventually being lost at the end of mitosis. (a-3) The B- and C-tubules form by a gamma-TURC-independent mechanism and grow until they reach the length of the A-tubule. (a-4) The distal end of the centriole is formed by elongation of the A- and B-tubules, creating a structurally distinct distal domain. (b) Centriole disengagement in the transition from M-G1. (i) A centrosome in metaphase of mitosis, with engaged mother centriole and procentriole. (ii) A centrosome in G1, after mitosis, with disengaged mother and daughter centrioles. The cartwheel has disassembled from the daughter centriole. Note that the subdistal appendages disassemble during mitosis, but the constituent proteins remain associated with the centriole. They are depicted as undifferentiated spheres in the mitotic centriole in place of the subdistal appendages. (Online version in colour.)