These new molecular insights into the way that cells divide could help scientists to understand how this process goes awry in cancer cells.
'We have been watching cells divide for more than 100 years, but we continue to seek to understand the molecular mechanisms involved. This is important because cell division is so central to life, and to certain diseases,' said Dr Gilles Hickson from the University of Montreal's Department of Pathology and Cell Biology, one of the lead authors of the study, which was published in Nature.
Cell division is a complex process that involves the duplication of chromosomes, followed by their separation to opposite ends of the cell. Next, the physical separation of the cells themselves – cytokinesis – results in two daughter cells, each containing its own set of chromosomes.
'Division is a... 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 Dr Hickson.
First studying fruit flies and then human cells, the researchers observed that as the chromosomes separated and moved towards opposite 'poles' of the cell, the membrane at these spots softened and relaxed – a process thought to be important for cytokinesis at the 'equator' of the cell. However, this occurred before the division machinery had even been assembled.
The chromosomes, previously thought to be passive players in cell division, were found to be the source of these relaxation cues. An enzyme complex – PP1-Sds22 – was found to travel with the separating chromosomes; the closer it got to the poles, the more softening it induced. The researchers inferred that it helps to establish synchrony and communication between the two steps of cell division – chromosome separation and cytokinesis.
All cancers are characterised by unchecked cell division, which means that the underlying mechanisms are potential targets for preventing the spread of cancer. 'But before we get there, we must continue to expand our knowledge about the basic processes and signals involved in normal cell division, to understand how they can go awry or how they can be exploited,' said Dr Hickson. 'Ultimately, this could help the rational design of more specific therapies to inhibit the division of cancer cells, ideally without affecting the healthy cells that are dividing at the same time.'