Biophysical Society Newsletter | September 2017

8

2017

BIOPHYSICAL SOCIETY NEWSLETTER

SEPTEMBER

Biophysical Journal Know the Editors Margaret Gardel University of Chicago

stiffening that occurs when an external force is ap- plied, might explain this difference. The actin cor- tex of cells contains myosin II, which we thought could “pre-stress” the networks. Once we realized that applied force was the relevant parameter, we were quickly able to match cell rheology measure- ments from several groups to the in vitro data I had collected. Within a few days, data I had col- lected over the course of several years became the basis of a manuscript that was published in PNAS that identified pre-stress as an important control parameter of cell rheology. The second “aha” moment occurred very recently. My lab has been working hard to understand how contractile forces arise in mixtures of actin filaments and myosin II motors. Other labs have been looking at mixtures of microtubules and microtubule-based motors and have described extensility in these systems. I have been puzzled the past few years over how different motor-filament arrays exhibit contraction or extension. Very recently, a postdoc and grad student in my lab have discovered that actomyosin mixtures can also exhibit extensility. The moment they showed me data resolved years of confu- sion! We, and others, are now discovering how to control the emergent properties of motor-filament systems to be either contractile or extensile. Q. How do you stay on top of all the latest developments in your field? This is very hard and I can’t say I do a perfect job of it. I agree to be the editor of relevant manuscripts submitted to Biophysical Journal and Molecular Biology of the Cell , two of my favorite journals. I agree to review papers. I also agree to review grants and am a standing member of a Na- tional Institutes of Health study section. I send my students and postdocs to meetings and ask them to report back to the lab on what they learned. My lab has a bi-weekly journal club: we are currently using the Pollard model in which every person has 10 minutes to present a paper of their choice.

Editor for the Molecular Machines, Motors, and Nanoscale Biophysics Section

Margaret Gardel

Q. What has been your biggest “aha” moment in science? There are two moments that come to mind. The first happened in graduate school. I had been studying the mechanical properties of cross-linked actin networks formed in vitro. I was visiting John Crocker’s lab at the University of Pennsylvania, where they were measuring the mechanical prop- erties of adherent cells. We were puzzling over why the stiffness I measured was 1000-fold softer than that measured in the adherent cell cortex, although protein concentrations were comparable. Then, we wondered if the non-linear elasticity of the in vitro networks, a dramatic