The balance between adhesion and contraction during cell division

Abstract

The ability to divide is a fundamental property of a living cell. The 3D orientation of cell division is essential for embryogenesis, maintenance of tissue organization and architecture, as well as controlling cell fate. Much attention has been placed on the mitotic spindle's role in placing itself along the cell's longest axis, where a shape sensing mechanism between a population of microtubules extending from mitotic centrosomes to the cell cortex occurs. However, contractile forces at the cell cortex also likely play a decisive role in determining the final placement of daughter cells following division. In this review, we discuss recent literature that describes the role of these contractile forces and how these forces could be balanced by mitotic adhesion complexes.

Figure 1.

A) Structured illumination microscopy micrograph of HeLa cell at metaphase, stained for α-tubulin (yellow), actin filaments (magenta) and myosin IIA (cyan). The mitotic spindle comprises spindle microtubules, that facilitate chromosome segregation and dictate furrow positioning, and astral microtubules that play a pivotal role in spindle positioning by interacting with the actin cortex. Myosin II is uniformly distributed at the cortex during metaphase. B) Upon anaphase onset, myosin II is enriched at the equator to ingress the cleavage furrow. Note the extensive contacts between the mitotic spindle and the contractile cortex, suggesting cross-talk between these two cytoskeletal networks. Note that the actin bundles protruding from the cells are not retraction fibers, as they are not attached to the substrate. Scale bar: 10 μm.

Figure 2.

A) Side view of a cell during cytokinesis. Green arrows denote the location of active integrins. B) Known adhesion components localized to mitotic cells include active β−1 integrin and paxillin. Classical focal adhesion complex during interphase. C) Under high adhesive conditions, cleavage furrow ingression is delayed from the bottom of the cell, generating asymmetry in shape. In addition, the daughter cell containing the mother centrosome makes more adhesions to the substrate and is flatter compared to the daughter cell with the daughter centrosome. The mother centrosome is also closer to the substrate. Legend shows individual components.

Figure 3.

Cortical and cytoplasmic actin filaments during metaphase (A) and cytokinesis (B). Upon mitotic entry, stress fibers disassemble, and the majority of actin filaments are assembled at the cell cortex. Recent studies have focused on a second population of actin filaments in the cytoplasm that is nucleated and regulated by centrosomes. Note the extensive actin filament network in the cytoplasm. This network may play a role in shape sensing and transmission of mechanical forces from the cortex to the mitotic spindle. Scale bar: 10 μm