IBMC researchers identify new mechanism controlling cell division

Mitosis is the process by which a cell divides to give rise to two identical daughter cells, with the same number of chromosomes and DNA as the parent cell. It is one of the most elegant and finely regulated biological processes that exists. Each phase of mitosis is strictly controlled in time, with severalcheckpoints identified that prevent an event from occurring before the previous event has been completed. In the latest issue of the journal Science, a team led by Helder Maiato, from Associate Laboratory of Molecular and Cellular Biology (IBMC) at the University of Porto, describes a spatial checkpoint that ensures that the nuclei of the two daughter cells are formed only when the chromosomes have moved apart properly, so that no chromosomes are left behind.

During mitosis, the cell's chromosomes align in pairs on the cell's equatorial plane. Each pair is then separated, and the chromosomes migrate along protein cables toward opposite poles of the cell. Hélder Maiato and his team discovered that a gradient of the Aurora protein acts as a kind of ruler in the cell, monitoring the positions of the chromosomes in relation to the equatorial plane and preventing nuclei from forming before the chromosomes are at a minimum safe distance. This new surveillance mechanism allows delayed chromosomes to be reintegrated into the new nuclei before the membranes surrounding them are completely formed.

When the Aurora protein gradient is disrupted, either globally or locally, the switch that links chromosome separation and the formation of new nuclei stops working, leading to abnormalities such as nuclei with too many copies of chromosomes or micronuclei within the cell. These situations can lead to diseases such as cancer, so understanding these mechanisms is a crucial step towards controlling them, with strong implications for human health.