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In honor of the ASCB (American Society for Cell Biology) annual meeting this week in Denver, Colorado, here’s an interesting paper by Shimamoto and colleagues that provides new findings in cell biology, and has been highlighted by three Faculty Members so far.

We’ve long marveled at the grace of mitosis, the process by which a eurkaryotic mother cell divides into two daughters. Recently, Shimamoto et al. shed light on the micromechanics of the all-important spindles that facilitate the segregation of chromosomes. A nice overview video from the paper (listed under ‘PaperFlick’) explains this a little further.

Two F1000 Faculty Members have given the paper an ‘Exceptional’ rating; Eugenio Marco and Gaudenz Danuser call this work “remarkable,” whilst Claire Walczak describes it as “creative, informative, and thought-provoking.”

In their study, Shimamoto and colleagues direct perturbed the metaphase spindles of Xenopus egg extracts with force-calibrated micro-needles under high-resolution microscopy, and monitored the movements and forces in action at different time scales. Shimamoto et al.’s findings show that spindle fibres exhibit both solid- and liquid-like properties in order to accommodate chromosomal movement without breaking (e.g. with the spindle being most viscous during chromosome motion). Spindle microtubules also respond flexibly to forces acting in diverse orientations, over a range of timescales, while still maintaining stability. The authors observed that microtubule bending and different crosslinking dynamics contribute to spindle elasticity and viscosity.

The work is perhaps best summed up by Marie-Hélène Verlhac, who concisely and eloquently states,

The spindle ensures accurate segregation of chromosomes. By directly applying forces and probing the spindle response using micro-needles, Shimamoto and colleagues discover unanticipated mechanical properties of this fascinating engine, which help understand the behaviour of chromosomes depending on their coordinates in the spindle.

The authors also suggest that there is important follow-up research to be done with regard to the reliable transport of cargos at high velocities in other cytoskeletal architectures, such as neurons.