During cell division, or mitosis, protein microtubules called spindles pull the replicated chromosomes apart before the cell splits in two. Stefania Castagnetti at Cancer Research UK in London and her group show that some yeast missing these spindles undergo a novel form of nuclear division — which may be a primitive form of mitosis.

Schizosaccharomyces pombe strains treated with a chemical that breaks down microtubules could still separate their chromosomes. By probing individual parts of the mitotic apparatus, the researchers surmise that, in the absence of spindles, the chromosomes remain associated with the cell's two spindle pole bodies, which normally act as anchors for the spindles. The authors suggest that these organelles move away from each other within the nuclear membrane, carrying the chromosomes along with them, before the nucleus divides.

PLoS Biol. 8, e1000512 (2010)