Separate to operate: control of centrosome positioning and separation

Abstract

The centrosome is the main microtubule (MT)-organizing centre of animal cells. It consists of two centrioles and a multi-layered proteinaceous structure that surrounds the centrioles, the so-called pericentriolar material. Centrosomes promote de novo assembly of MTs and thus play important roles in Golgi organization, cell polarity, cell motility and the organization of the mitotic spindle. To execute these functions, centrosomes have to adopt particular cellular positions. Actin and MT networks and the association of the centrosomes to the nuclear envelope define the correct positioning of the centrosomes. Another important feature of centrosomes is the centrosomal linker that connects the two centrosomes. The centrosome linker assembles in late mitosis/G1 simultaneously with centriole disengagement and is dissolved before or at the beginning of mitosis. Linker dissolution is important for mitotic spindle formation, and its cell cycle timing has profound influences on the execution of mitosis and proficiency of chromosome segregation. In this review, we will focus on the mechanisms of centrosome positioning and separation, and describe their functions and mechanisms in the light of recent findings.

Centriole structure

“…C-Nap1 interacts with rootelin and LRRC45 [65], potentially forming the fibrous bundle linking the centrioles. The regulation of centriole cohesion is an important issue in licensing centriole duplication and in spindle formation (see [66,67]). …”

A comparative overview of the sperm centriolar complex in mammals and birds: Variations on a theme

“…When present, the PC in both vertebrate groups is short [0.3µm in the ostrich (Soley, 1993) and approximately 0.5µm in mammals as in somatic cells (Agircan et al, 2014)], lies partially within the implantation fossa at the base of the nucleus, and displays the characteristic pinwheel arrangement of microtubular triplets embedded in a ring of moderately electron-dense material (Avidor-Reiss et al, 2015;Sathananthan, 2012;Soley, 8 1993) (Fig. 2b).…”

“…The essential role of the protein centrobin in the assembly of the "head-tail coupling apparatus" during spermiogenesis points to a possible molecular basis for the formation of acephalic sperm (Liška et al, 2009). Work on the factors responsible for positioning of the centrosome in somatic cells may also shed further light on this phenomenon (Agircan et al, 2014).…”

Centrosomes back in the limelight

“…Regulating this distance could be part of differentiation programmes that set where microtubules are operating in a given cell and thus contribute to facilitate tissue organogenesis or response to extracellular cues. Having such a time delay between the biogenesis of the two units imposes a slow differentiation process, with the distinct control of centriole length as well as the timely control of disengagement of the two centrioles at mitotic exit, after the two diplosomes have separated at the G2/M transition (see the article by Elmar Schiebel and collaborators) [70].…”