Research

Holding Steady

When mammalian cells prepare to divide, they have an internal toroidal flow that seems like it would destroy the protein spindle within the cell.

Before a mammalian cell divides, the spindle — a protein structure — divides the cell’s genetic material in two. As it does, the cytoplasm inside the cell forms a toroidal flow (below, left). Researchers wondered how the spindle manages to stay in place with this flow; the spindle sits just where the flow diverges, a spot that seems ripe for unstable shifts in position. But, contrary to expectations, their analysis showed that — although a smaller spindle would be unstable in that spot — the protein spindle is large enough that its size distorts the cell’s flow and creates a pressure that moves it back into place if it shifts. (Image credit: top – ColiN00B, illustration – W. Liao and E. Lauga; research credit: W. Liao and E. Lauga; via APS Physics)

Left: illustration of the toroidal flow near the spindle (purple) in a cell. Right: schematic of flow near the spindle's fixed point.
Left: illustration of the toroidal flow near the spindle (purple) in a cell. Right: schematic of flow near the spindle’s fixed point.
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