Limited Resources Induce Bistability in Microtubule Length Regulation

TL;DR

This paper presents a theoretical model showing that limited resources can cause microtubule length regulation to become bistable, with experimental validation revealing bimodal length distributions.

Contribution

It introduces a novel model incorporating resource limitations, demonstrating bistability in microtubule length regulation, supported by experimental evidence.

Findings

Bistability occurs under resource-limited conditions.

Experimental data shows bimodal microtubule length distribution.

Resource constraints significantly affect microtubule dynamics.

Abstract

The availability of protein is an important factor for the determination of the size of the mitotic spindle. Involved in spindle-size regulation is kinesin-8, a molecular motor and microtubule (MT) depolymerase, which is known to tightly control MT length. Here, we propose and analyze a theoretical model in which kinesin-induced MT depolymerization competes with spontaneous polymerization while supplies of both tubulin and kinesin are limited. In contrast to previous studies where resources were unconstrained, we find that, for a wide range of concentrations, MT length regulation is bistable. We test our predictions by conducting in vitro experiments, and find that the bistable behavior manifests in a bimodal MT length distribution.