Durcan et al. report.
When chromosomes begin to pull apart during mitosis, the microtubules in the middle of the cell bunch up into a structure known as the central spindle. As the new cell begins to pinch off, it remains connected to its parent by a tether, the midbody, which contains the central spindle and doesn't part until after division is complete. Microtubules in developing flagella and cilia are arranged with the help of a protein called Tektin 2. Durcan et al. were therefore curious whether this protein performs a similar job in the midbody tether.
To determine the protein's function, the scientists slashed its levels with siRNA. Although Tektin 2–lacking cells seemed to divide normally, they often reunited. For a closer look at what occurred in the central spindle, the team treated cells with blebbistatin, which prevents dividing cells from pinching in two. Microtubules in the central spindle normally form a bundle, but they were jumbled in blebbistatin-treated cells dosed with Tektin 2 siRNA.
The team concluded that Tektin 2 promotes cell separation by bundling the microtubules of the central spindle. How Tektin 2 achieves this feat isn't clear, but they hypothesize that it sets the length of microtubules in the central spindle, controlling how much overlap occurs between microtubules from the would-be parent and offspring cells.