PUBLICATIONS: Discovery by IBMC researchers published in Science

Discovery of an intracellular navigation system published in Science by IBMC researchers

A team of researchers led by Helder Maiato has proved that there is a sort of Highway Code within cells, a finding - whose article was published in Science - that shifts the way in which we perceive how chromosomes move during cell division. By using chromosome transport as a model to explain this navigation system, the research team demonstrates how this signaling mechanism conditions the path through which molecular transporters travel. IBMC researchers show that the existence of specific signals on microtubules - which resemble intracellular highways – give directions to chromosomes of which route to take in the course of cell division.   

Helder Maiato and his team focused on the exact moment when cells assemble a new microtubule network, which is then arranged as a very well-known structure: the mitotic spindle. “During cell division a microtubule network is established with a very specific function: settle the chromosomes in the spindle equator so that they can then split equally between the two daughter cells”, explains Marin Barisic, the article’s first author. Most chromosomes “are, from early on, stationed right in the middle of that network”, in the spindle apparatus, waiting for the split to occur. But some chromosomes are stationed outside the parking zone, thus being forced to trail their way, first to the cell’s poles and from there to the spindle equator.

These stray chromosomes begin by attaching themselves to any microtubule from the network, which covers almost every nook and cranny, a bit like a network of secondary roads of the mitotic spindle. The chromosomes then head on to the poles’ main sector, the centrosomes, and continue on through the main roads until they reach the spindle equator’s parking zone.   

In the midst of this process, the researchers noticed one of the chromosome carriers that wanders the spindle – the motor protein CENP-E – and focused their attention on it; additionally, the researchers selectively added and removed, in different experiments, a signal from the microtubules, tyrosine. Helder Maiato explains that “whenever we change the signals across the microtubules, there is a major shift in the way chromosomes circulate”. If every microtubule is signaled with tyrosine, the chromosomes will come to a halt near the centrosomes”. If, on the contrary, the whole mitotic spindle is stripped of every tyrosine signal, the chromosomes go beyond the poles and get off-track in the secondary roads. The researcher explains that “if the microtubule has traces of tyrosine, the CENP-E carrier rests and doesn’t transport any chromosomes from the pole; but should the microtubules have no tyrosine signal, as it happens with the system’s main microtubules, the CENP-E tows the chromosomes to the spindle equator”. This whole process is described in an infographic video.

After the genetic code and epigenetics, the new revolution may very well lie in this code – microtubules’ code.