Experimental methods to control pinned and coupled actomyosin contraction events

TL;DR

This paper introduces experimental techniques for controlling and measuring actomyosin contraction by anchoring networks to surfaces with adjustable rigidity, enabling detailed study of force generation and environmental interactions.

Contribution

It presents novel methods for spatially controlling actomyosin anchoring and calibrating contractile forces, advancing understanding of actomyosin's mechanical role in cellular processes.

Findings

Calibration of flexure hinges for force measurement

Demonstration of pinned and coupled contraction modes

Quantitative assessment of actomyosin-generated forces

Abstract

Actin and myosin drive many instances of force generation, deformation, and shape change in cells, tissues, and organisms. In particular, cytoskeletal actomyosin is remarkable in its adaptive architecture, responding to a host of actin-binding proteins. Equally important, however, is actomyosin's interaction with its mechanical environment. Actomyosin contractility and environmental properties, such as geometry and stiffness, are inherently coupled. To understand this coupling, novel experimental techniques are needed. Here we describe methods to spatially control the anchoring of reconstituted contractile actomyosin networks to two, opposing surfaces ("transverse anchoring"). The two surfaces can be either rigid ("pinned contraction"), or one of the surfaces may be compliant ("coupled contraction"). We introduce compliance by manufacturing flexure hinges, and describe their calibration. Calibration permits a direct measurement of the contractile force and mechanical work that actomyosin exerts on the environment. The methods described here provide an avenue toward a more complete characterization of actomyosin's role as an actuator, an essential property in its context of driving deformation and shape change in living systems.