Fig. 4.

Mitotic spindle organization in the C. elegans embryo. a Schematic representation of the C. elegans centrosome, with a pair of centrioles surrounded by pericentriolar material (PCM) and minus-end nucleated/anchored microtubules. b Functional levels of the centrosome. Cartoon illustrating core proteins responsible for centriole duplication (first level) and PCM assembly (second level). Proteins of the third level influence microtubule nucleation, polymerization and depolymerization. The aurora kinase AIR-1 is involved at multiple steps, in both the maturation of the centrosome and the regulation of downstream effectors. c Ultrastructural pathway of centriole duplication in C. elegans early embryos (modified from [68]). d Partial reconstruction of a metaphase half-spindle. Microtubules that contact the chromosomes (green) are designated kinetochore microtubules (shown in yellow). Other microtubules are displayed in red. Microtubule ends in the spindle pole, surrounding the centriole pair (blue cylinders), are indicated by white spheres. e Kinetochore microtubules have an open, flared plus-end morphology (upper row). About 80% of the microtubules in the centrosome (lower row) have closed, capped minus ends (arrowhead), although some microtubules with open ends (arrows) are observed (modified from [71])