Let’s kick off the Fourth of July weekend with some biological fireworks! While we’ve added a few pyrotechnic sound effects just for fun, what you see in this video is the product of some serious research. Using a specialized microscope equipped with a time-lapse camera to image fluorescence-tagged proteins in real-time, an NIH-funded team has captured a critical step in the process of cell division, or mitosis: how filaments called microtubules (red) form new branches (green) and fan out to form mitotic spindles.
In this particular experimental system, the team led by Sabine Petry at Princeton University, Princeton, NJ, studies the dynamics of microtubules in a cell-free extract of cytoplasm taken from the egg of an African clawed frog (Xenopus laevis). Petry’s ultimate goal is to learn how to build mitotic spindles, molecule by molecule, in the lab. Such an achievement would mark a major step forward in understanding the complicated mechanics of cell division, which, when disrupted, can cause cancer and many other health problems.
A recipient of an NIH Director’s 2016 New Innovator Award, Petry has previously shown that at the start of cell division a small protein called Ran, which gets activated around the chromosomes, stimulates microtubule branching . The activation of Ran, like clicking on a master switch, frees up hundreds of other proteins to self-assemble and form into the complex molecular machinery required for cell division. Petry found that one of these “freed-up” proteins, called TPX2, appears to team with certain protein complexes and potentially other still-unknown proteins, to stimulate the microtubule branching shown in this video.
Raymundo Alfaro-Aco and Akanksha Thawani, graduate students in the Petry lab, recently discovered that a specific region of TPX2 seems to activate the ring-like protein complex gamma-TuRC, which prompts microtubules to branch in the fan-like pattern that you see above . In fact, Thawani recorded this video—part of Princeton’s 2017 Art of Science exhibit—as a positive control to test whether microtubules in the lab’s cell-free system were branching correctly before performing an experiment.
 Branching microtubule nucleation in Xenopus egg extracts mediated by augmin and TPX2. Petry S, Groen AC, Ishihara K, Mitchison TJ, Vale RD. Cell. 2013 Feb 14;152(4):768-777.
 Structural analysis of the role of TPX2 in branching microtubule nucleation. Alfaro-Aco R, Thawani A, Petry S. J Cell Biol. 2017 Apr 3;216(4):983-997.
Petry Lab (Princeton University, Princeton, NJ)
Petry Project Information (NIH RePORTER)
NIH Director’s 2016 New Innovator Award (Common Fund)
NIH Support: National Institute of General Medical Sciences; Common Fund