During cell division, our genome must be faithfully transmitted from the mother cell to daughter cells. This task is done by the spindle, the micron-sized bipolar force-generating machinery. Using a microfabricated force sensor and high-resolution microscopy, a team of Yuta Shimamoto at National Institute of Genetics and Yusuke Maeda at Kyushu University probed the local mechanical architecture of the spindle (Fig. 1A) and found its substantial heterogeneity; the equator and pole regions are stiff whereas its middle is more flexible and deformable (Fig. 1B). The spindle’s mechanical heterogeneity explains how this micron-sized structure can maintain its local functional architectures, such as the pole and the equator, required to pull chromosomes and determine the cell division axis, while adapting the overall structure to perturbations. Their physical approach will help understand the mechanisms ensuring the fidelity of chromosome segregation, which is essential for normal cell proliferation and embryonic development in humans.

Figure: (A) The local mechanical architecture of the spindle was probed using a fiber-shaped microforce sensor. (B) The spindle was found to have a substantial mechanical heterogeneity (depicted in different colors), suggesting its robust yet adaptable nature required for error-free cell division.