Mitosis, the precise division of the nucleus, is required for multicellular life. Unsurprisingly then, mitosis has remained essentially the same over approximately two billion years of evolution. However, the individual components involved in mitosis have not. For example, in order for the chromosomes to segregate properly during nuclear division, they require a scaffold known as the mitotic spindle. Reza Farhadifar of Harvard University, UF Dept. of Biology Associate Professor Charles Baer, and their collaborators show in a recent paper in Current Biology that the mitotic spindle exhibits extensive variation both within and between closely related species of nematodes in the genus Caenorhabditis. The effect of mutation on the spindle, together with stabilizing selection on embryo size, quantitatively explains the levels of within-species variation in the spindle and its diversity over 100 million years of evolution, despite conservation of the overall mitotic process. Here is the link to Dr. Baer’s Mitosis paper at Cell.com
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