Mitosis is a cellular process in which the genetic information encoded in chromosomes is distributed to two identical daughter cells. Mitosis is thus a fundamental characteristic of all living beings on our planet. Researchers from the Alexander Dammermann's group at the Max Perutz Labs, a joint venture of the University of Vienna (Universität Wien) and the Medical University of Vienna (Medizinischen Universität Wien), have investigated how centrioles contribute to this process.
Mitosis forms a filamentous spindle that ensures that chromosomes are properly distributed and positioned at opposite ends of the cell. Similar to load ropes, the spindle also needs a reference point from which it can develop. This point is formed by centrioles, which accumulate around a network of proteins, the so-called pericentriolar material (PCM), and thus form centrosomes. These serve as starting and anchor points for the spindle threads.
It was previously known that centrioles were essential for the formation of the centrosome, but their role in the subsequent growth phase and in maintaining PCM during cell division was unclear. The researchers succeeded in answering these questions with the help of the nematode threadworm C. elegans.
This model organism has a particularly large centrosome. With the help of laser beams, the centrioles inside the centrosome could be removed during mitosis without destroying the entire structure: "We found out that, contrary to expectations, removing the centrioles did not lead to an immediate collapse of the PCM. However, further growth was very limited, which illustrates the important role of centrioles in the formation of the PCM and thus of the spindle apparatus," explained the main authors.
In addition to their role in the formation of the PCM, centrioles were also essential for its structural integrity. Without centrioles, the centrosome was literally pulled apart in the later course of cell division. This result was particularly remarkable for the researchers because the centrioles are very small compared to the PCM. How they can maintain the structural integrity of a structure more than 30 times larger remains to be seen.
The authors suspect that the centrioles are anchor points for proteins which, like bars in reinforced concrete, provide the tensile strength of the PCM. By controlling the growth of the PCM and its structural integrity, centrioles fulfill their crucial role during the cell division process.