: In a cell-free experimental system, interacting microtubule asters (green) recruit cytokinesis signals (Aurora B kinase, magenta). Credit: Phuong A. Nguyen, Harvard Medical School and MBL

In a cell-free experimental system, interacting microtubule asters (green) recruit cytokinesis signals (Aurora B kinase, magenta). Credit: Phuong A. Nguyen

Building a cell from its components is a synthetic approach to understanding cell biology that has emerged as a hot research goal in the past few years. Recently, a team of MBL visiting scientists from Harvard Medical School built a fully controllable, cell-free experimental system that allows them to visualize and study the final phase of cell division (cytokinesis), when the cell splits in two. This system consists of supported lipid bilayers that mimic the cell membrane, artificial centrosomes, and extract from the cytoplasm of frog (Xenopus) eggs. It represents the first-ever reconstitution of cytokinesis signaling outside of living cells. The group was able to assemble arrays of antiparallel microtubules that recruit cleavage furrow proteins that signal to the “cell cortex.” The spatial scale was unusually large, since Xenopus eggs are huge relative to human tissue cells, and as a result the team could query the biophysics of cytokinesis signaling over many minutes and many microns using powerful imaging modalities, notably TIRF (total internal reflection fluorescence) microscopy. This led them to several significant mechanistic discoveries. The research team included Phuong Nguyen, Aaron Groen, Martin Loose, Keisuke Ishihara, Martin Wuhr, Christine Field, and Timothy Mitchison. (Science, doi: 10.1126/science.1256773, 2014).