29 September 2021 Thesis defense Lotte van Rijnberk: “Regulation and function of developmentally controlled polyploidization” Back to news Lotte van Rijnberk, from the group of Matilde Galli, successfully defended her thesis “Regulation and function of developmentally controlled polyploidization” on 29 September 2021. She investigated the function of cells that have two nuclei and more than two copies of each chromosome – so-called polyploid cells – in the microscopic roundworm. Such cells turn out to be important for the regulation of gene activity in the intestines during development. “Polyploid cells are also present in human tissue during development, which makes it important to study their exact function,” says Van Rijnberk. During cell division, the DNA in a cell is doubled, after which it is divided over two new daughter cells. Both new cells then contain two copies of each chromosome and are therefore called diploid cells. Sometimes, however, the DNA is not divided over the two daughter cells, but remains in one cell. Consequently, this cell has more than two copies of each chromosome, divided over two or more cell nuclei, and is called a polyploid cell. Function of polyploidization Polyploid cells are formed in a regulated manner during the development of various organisms and in different types of tissue. However, its function remains unclear. During her PhD, Lotte van Rijnberk therefore researched the use of cells with multiple nuclei. She studied the intestines of the microscopic roundworm (caenorhabditis elegans), which is an ideal model system for research into both the regulation as well as the function of polyploidization. Supporting egg cells Together with her colleagues, she found that having two nuclei is important for the regulation of gene activity in the intestines. When the researchers made sure that there were only cells with a single nucleus present in the intestines, the offspring developed less successfully. That is because the intestines are important for supporting egg cells. “Many human tissues also contain polyploid cells during development. If something goes wrong there, it can affect someone’s health. That is why it is important to further study this,” Van Rijnberk explains. Rollercoaster She calls her PhD trajectory a rollercoaster. “I really enjoyed watching the worms under the microscope. And I have been able to develop my skills enormously, for example in the area of data analysis.” But the real highlight was formed by her fellow PhD students, with whom she could share everything. “Research almost never goes according to plan, which can be frustrating. It is really nice to have companions, who you can share your worries with but also do fun things with.” Social activities She therefore wants to encourage people who are just starting their PhD trajectory to stay in touch with colleagues. “It’s a shame that there were so few social activities the past period because of corona, but don’t miss out now that they are slowly starting up again. These activities make it so much fun here at the Hubrecht”, says Van Rijnberk. The completion of her PhD therefore receives a fitting celebration. “A big party with a DJ, lots of dancing.” Now that she obtained her PhD, Lotte van Rijnberk is orienting herself towards a career in molecular biology with a clinical relevance.