Collective Organization of Microtubules and Motors

In vitro systems of purified microtubules and motor proteins offer a greater degree of biochemical control compared with living systems. Can bulk microtubule network contractions be recapitulated with purified motors? In collaboration with Richard McKenney at UC Davis and Claire Walczak at IU we're studying collective behaviors of microtubules and motors proteins.

​R Tan, PJ Foster, DJ Needleman, RJ McKenney, "Cooperative Accumulation of Dynein-Dynactin at Microtubule Minus-Ends Drives Microtubule Network Reorganization", bioRxiv 2017; doi:10.1101/140392  submitted
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Active Contraction of Microtubule Networks

We discovered that networks composed of stabilized microtubules in Xenopus oocyte extract undergo a spontaneous contraction on the millimeter length scale, due to the clustering of microtubule minus ends by the motor protein dynein. In collaboration with Michael Shelley and Sebastian Fürthauer at NYU, we developed an Active Fluid model that can quantitatively describe the contraction process.

PJ Foster, S Fürthauer, MJ Shelley, DJ Needleman, “Active contraction of microtubule networks”, eLife 2015;4:e10837; doi:10.7554/eLife.10837

​PJ Foster*, W Yan*, S Fürthauer, MJ Shelley, DJ Needleman, "Connecting macroscopic dynamics with microscopic properties in active microtubule network contraction", 2017 submitted​    ​(* denotes co-first authors)

Bayesian Analysis of FLIM Data

Fluorescence Lifetime Imaging Microscopy (FLIM) is a spectroscopic method where changes in the lifetime of a fluorophore are used to infer changes in the fluorophore's local environment. How can one cope with noisy FLIM data? One approach is to use Bayesian inference to combine measured data with knowledge about the system. I helped to develop and test a FLIM analysis technique based on Bayesian statistics, which can be used to accurately infer fluorescence decay parameters in noisy regimes. This approach was then used to develop a technique to measure polymer assembly in cells and cell extracts.

​B Kaye*, PJ Foster*, TY Yoo*, DJ Needleman, "Developing and Testing a Bayesian Analysis of Fluorescence Lifetime Measurements",PLoS ONE 2017;12(1);e0169337;
​doi:10.1371/journal.pone.0169337
(* denotes co-first authors)

B Kaye, TY Yoo, PJ Foster, CH Yu, DJ Needleman, "Bridging length scales to measure polymer assembly", Mol. Biol. Cell 2017; 28(10); 1379-1388; doi:10.1091/mbc.E16-05-0344

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Motor Proteins in Spindles

Spindles are biochemically complex environments where many different kinds of motor proteins act in concert to organize dynamic microtubules. What framework can be used to understand the collective effects of these motor-microtubule interactions and to understand effects on the spindle scale in terms of the interactions between individual components?

Microtubule Interactions in Xenopus extracts

​Microtubules in the spindle are organized by molecular motor proteins. Outside of the spindle these same motor proteins can organize microtubules into a wide range of structures, from asters to "bilayers". What is the detailed structure of these assemblies and what rules of interaction between microtubules give rise to these distinct morphologies?