Canadian and British researchers have discovered that chromosomes play an active role in animal cell division. This occurs at a precise stage - cytokinesis - when the cell splits into two new daughter cells. It was observed by a team of researchers including Gilles Hickson, an assistant professor at the University of Montreal's Department of Pathology and Cell Biology and researcher at the CHU Sainte-Justine Research Centre, his assistant Silvana Jananji, in collaboration with Nelio Rodrigues, a PhD student, and Sergey Lekomtsev, a postdoc, working in the group led by Buzz Baum of the MRC Laboratory for Molecular Cell Biology at University College London. Their findings were published today in Nature. Cell division is fundamental to all life forms: the human body develops from a single cell that divides billions of times to generate all tissue types, and some of these cells continue to divide billions of times every day throughout life. For the moment, however, the molecular mechanisms involved are incompletely understood, and it was unknown until now that chromosomes could play an active role at this step in cytokinesis. 

Flawless division

In animal cells, division involves mitosis, the separation of chromosomes followed by splitting of the cell into two new daughter cells by cytokinesis. "Division is a complex and robust process that is generally performed flawlessly, but when an error occurs in DNA separation or during cytokinesis, it can be a source for triggering cancer, for example," said Hickson.

It is well known that microscopic cable-like structures, called microtubules, were involved in pulling chromosomes to opposite poles of the cell during the division process. "At this time, microtubules physically separate the chromosomes via their central kinetochores while other microtubules signal to the cortex of the cell where its equator is, i.e., where division will take place," Hickson explained. Furthermore until now, it was believed that the chromosomes only played a passive role: that they were pulled by the microtubules and didn't affect cytokinesis, but this is not the case.