An actin network can move chromosomes during cell division, scientists report in this week's
"The mechanism described [by the group] is so unexpected and beautiful. I never saw even a hint of something like that," said Alex Mogilner, from University of California, Davis, who was not involved in the research. He told
Jan Ellenberg and colleagues at the European Molecular Biology Laboratory in Heidelberg followed meiosis in starfish (
"We could visualize for the first time with 4-D images that chromosomes nucleate actin filaments directly, and that this process is essential for chromosome movement and, thus, to prevent chromosome loss," first author Péter Lénárt told
"We were interested in understanding how microtubules reorganize at the time of nuclear envelope breakdown [NEBD]. By labeling microtubules in live cells, we noted that after NEBD, microtubule asters were much too short to capture distal chromosomes more than 40 m away from centrosomes," continued Lénárt. "Since most cellular movements are mediated by either the microtubule or the actin cytoskeleton, it wasn't difficult to guess that, if not microtubules, then actin must drive chromosome congression."
"I think the data are very solid and convincing," Claire Walczak, from Indiana University, Bloomington, who did not participate in this study, told
"No one has ever shown that actin moves chromosomes," said senior author Jan Ellenberg. "We were able to do so because our group is one of the few that studies cell division in starfish–an ideal model for observing division in living animal eggs–in a very fruitful collaboration with Mark Terasaki at the Marine Biological Laboratory."
Indeed, a key point of the work was the choice of organism. Starfish oocytes are transparent and develop simply in seawater, which renders them an excellent specimen for live cell microscopy. In addition, starfish are evolutionary close to vertebrates.
"Using starfish oocytes, Lénárt et al. have discovered a fundamental biological mechanism that is likely to apply to mammalian oocytes as well. This is another great example of a centrally important concept emerging from the study of echinoderm oocytes," Laurinda Jaffe from University of Connecticut Health Center in Farmington, who did not participate in this study, told