The tumour suppressor DLC2 ensures mitotic fidelity by coordinating spindle positioning and cell-cell adhesion.

Elisa Vitiello,Maria S Balda,Jorge G Ferreira,Helder Maiato,Karl Matter

doi:10.1038/ncomms6826

Abstract

Dividing epithelial cells need to coordinate spindle positioning with shape changes to maintain cell–cell adhesion. Microtubule interactions with the cell cortex regulate mitotic spindle positioning within the plane of division. How the spindle crosstalks with the actin cytoskeleton to ensure faithful mitosis and spindle positioning is unclear. Here we demonstrate that the tumour suppressor DLC2, a negative regulator of Cdc42, and the interacting kinesin Kif1B coordinate cell junction maintenance and planar spindle positioning by regulating microtubule growth and crosstalk with the actin cytoskeleton. Loss of DLC2 induces the mislocalization of Kif1B, increased Cdc42 activity and cortical recruitment of the Cdc42 effector mDia3, a microtubule stabilizer and promoter of actin dynamics. Accordingly, DLC2 or Kif1B depletion promotes microtubule stabilization, defective spindle positioning, chromosome misalignment and aneuploidy. The tumour suppressor DLC2 and Kif1B are thus central components of a signalling network that guides spindle positioning, cell–cell adhesion and mitotic fidelity.

Highlights

Dividing epithelial cells need to coordinate spindle positioning with shape changes to maintain cell–cell adhesion
Spindle positioning is determined by astral microtubules that originate at the spindle poles and extend towards the cell cortex where they are thought to interact with actin structures that transmit extracellular cues[2]
Mitotic cells exhibited striking defects in integrity of tight and adherens junctions with gaps appearing between neighbouring human corneal epithelial (HCE) cells, one of the cell lines used for the short interfering RNA screen described by Elbediwy et al.[21] (Fig. 1a,b and Supplementary Fig. 1a)

Summary

Introduction

Dividing epithelial cells need to coordinate spindle positioning with shape changes to maintain cell–cell adhesion. We demonstrate that the tumour suppressor DLC2, a negative regulator of Cdc[42], and the interacting kinesin Kif1B coordinate cell junction maintenance and planar spindle positioning by regulating microtubule growth and crosstalk with the actin cytoskeleton. Spindle positioning is determined by astral microtubules that originate at the spindle poles and extend towards the cell cortex where they are thought to interact with actin structures that transmit extracellular cues[2] It is poorly understood how astral microtubules are regulated to ensure proper spindle positioning and whether such mechanisms affect cell–cell adhesion to maintain the tissue integrity during mitotic cell shape changes. We show that the tumour suppressor DLC2, a GAP (GTPase-activating protein) for Cdc[42], regulates microtubule growth and cortical actin polarization, and, thereby, coordinates spindle positioning and junctional integrity. The DLC2 regulatory network is required for mitotic fidelity, providing a molecular explanation for its tumour suppressor activity

Methods

Results

Conclusion