Key discovery on microtubule dynamics

Cell division is essential for the survival, reproduction and growth of all organisms. To separate equally the chromosomes between two daughter cells, microtubules of the mitotic spindles attach chromosomes and pull them apart. Microtubules have always been described as built from GDP-tubulin lattice with a GTP-tubulin cap at their plus end. When the GTP-tubulin cap is cleaved to GDP-tubulin via a process called hydrolysis, microtubules depolymerize creating a pulling force that move chromosomes.

The discovery of a third zone in microtubules

In their study published in Nature Communications, scientists of the Meraldi group identified for the first time a marker for pure GDP-tubulin in the mitotic spindle. This marker revealed on growing microtubules a third mixed zone composed of both GTP- and GDP-tubulin that lies between the GDP-tubulin lattice (green in movie below) and the GTP-cap (pink). This mixed nucleotide zone, which reflects GTP-tubulin hydrolysis, occupied almost a third of the total length of the microtubules, which was much longer than expected.

A new mixed-nucleotide zone (black zone) can be seen between the GDP-tubulin lattice (green) and the kinetochores (pink), where the GTP-cap is located. © UNIGE

What’s next?

These findings allow to visualize for the first time the rate of GTP-tubulin hydrolysis in the mitotic spindle, a fundamental parameter of microtubule dynamics. The team of Prof. Patrick Meraldi will now use this tool to identify key regulators of microtubule dynamics that could be used in the long-term as a lever to control cell division.

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