Cytokinesis in Metazoa and Fungi

Abstract

SUMMARYCell division-cytokinesis-involves large-scale rearrangements of the entire cell. Primarily driven by cytoskeletal proteins, cytokinesis also depends on topological rearrangements of the plasma membrane, which are coordinated with nuclear division in both space and time. Despite the fundamental nature of the process, different types of eukaryotic cells show variations in both the structural mechanisms of cytokinesis and the regulatory controls. In animal cells and fungi, a contractile actomyosin-based structure plays a central, albeit flexible, role. Here, the underlying molecular mechanisms are summarized and integrated and common themes are highlighted.

Figure 1.

Cytokinesis in metazoa. (A) Overview of the mechanism of division-plane positioning. Furrow position is determined by the position of the mitotic spindle. Positive signals from the spindle midzone and bundled astral microtubules cooperate with inhibitory signals from dynamic astral microtubules to position the division plane. (B) Pathway that induces accumulation of contractile ring components. Components conserved between metazoa and yeast are highlighted in blue. (C) Spatial organization of the activators of contractile ring components and schematic depicting the contractile ring assembled from short actin filaments. GAP, GTPase-activating protein; GEF, GDP–GTP exchange factor.

Figure 2.

Cytokinesis in the fission yeast Schizosaccharomyces pombe. (A) Overview of the mechanism of division-plane positioning. The contractile ring assembles at a site that is determined by the position of the nucleus in G₂ phase. Interphase microtubules serve to position the nucleus near the cell center. (B) Pathway that induces accumulation of components of the contractile ring. Components conserved between yeast and metazoa are highlighted in blue. (C) Schematic depicting the assembly of an actomyosin-based contractile ring from a broad band of cytokinetic nodes that progressively align by means of the so-called search–capture–pull–release mechanism. Note also the relationship between the ingressing contractile ring and the required remodeling of the cell wall materials through septum deposition.

Figure 3.

Cytokinesis in the budding yeast Saccharomyces cerevisiae. (A) Overview of the mechanism of division-plane positioning. The contractile ring assembles at the neck of the bud, which is positioned in early G₁ phase. The spindle is positioned relative to the bud neck during anaphase. (B) Pathway that induces accumulation of components of the contractile ring. Components conserved between metazoa and yeast are highlighted in blue. (C) Spatial organization of the yeast contractile ring, highlighting the relationship between the ingressing contractile ring and the required remodeling of the cell wall materials through septum deposition. GAP, GTPase-activating protein; GEF, GDP–GTP exchange factor.

Figure 4.

Abscission in metazoa. Cell separation is mediated by endosomal sorting complex required for transport III (ESCRT-III) filaments that assemble in constriction zones that flank the centralspindlin-dense midbody. The remaining microtubules are depolymerized by spastin, and the membrane scission process itself is driven by ESCRT-III filaments that constrict the neck of the cytoplasmic bridge between the two daughter cells.