IBMC researchers identify new mechanism for controlling cell division

Mitosis is the process by which a cell divides to produce two identical daughter cells with the same number of chromosomes and DNA as the mother cell. It is one of the most elegant and finely regulated biological processes in existence. Each phase of mitosis is strictly controlled in time, and severalcheckpoints have been identified that prevent an event from occurring before the previous event has finished. In the most recent issue of the journal Sciencea team led by Helder Maiato, from the Associate Laboratory Instituto de Biologia Molecular e Celular (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 chromosome is left behind.

During mitosis, the cell's chromosomes line up in pairs in the equatorial plane of the cell. Each pair is then separated, and the chromosomes migrate along protein cables towards the 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 disturbed, either globally or locally, the switch that connects the separation of chromosomes and the formation of new nuclei stops working, giving rise to anomalies such as nuclei with too many copies of chromosomes or micro-nuclei inside the cell. These situations can lead to disease, such as cancer, so understanding these mechanisms is a crucial step towards controlling them, with major implications for human health.