The mitotic spindle reveals unsuspected variations

“In vitro studies appeared to indicate that the mitotic spindle was always the same, in all cells and at all times. But our in vivo research shows morphological variations,” explains Véronique Marthiens, a researcher in Renata Basto's team, Biology of centrosomes and cilia. The mitotic spindle is a structure inside cells that guides chromosomes (DNA) to opposite ends of the cell during the division (mitosis) process.

Once genetic matter has been evenly divided between both ends, the cell can then split down the middle, giving way to two new cells that each house a copy of the original DNA. But cell division dysfunction can give rise to serious cerebral deformations, such as microcephaly, in which babies are born with abnormally small brains. Diana Vargas-Hurtado, one of the team’s PhD students, studied this phenomenon in animals, and noticed that mitotic spindles look completely different in the early stages of nervous system development, during gestation and upon birth. In the early stages, their morphology facilitates the emergence of genetic anomalies. The student went even further, and identified the protein, Tpx2, responsible for altering the appearance of mitotic spindles between the early and later stages. “We want to gain a better understanding of these mechanisms, especially since anomalies in how the nervous system develops are characterized by insufficient cell growth, while cancer is linked to excessive growth. What’s more, Tpx2 has already been shown to interact with another molecule, Aurora, which is sometimes targeted in cancer treatments,” she adds.

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Renata Basto's team