3 November Thesis defense Stijn Sonneveld: “Gene expression in sight” Back to news Stijn Sonneveld, from the group of Marvin Tanenbaum, successfully defended his thesis “Gene expression in sight: Single-molecule studies of gene expression control” on 3 November 2021. Using new, innovative techniques, he studied three processes that play an important role in gene regulation. His thesis not only contributes to our knowledge about the functioning of the human body, but also helps us understand what goes wrong in diseases such as cancer or Alzheimer’s. The human body consists of trillions of cells, but not all of these cells are exactly the same. There are for example skin cells, muscle cells and nerve cells, each with different traits and functions. Given that all these cells contain the exact same DNA, how do the differences between them arise? Stijn Sonneveld explains: “That is due to the way cells read the DNA. A muscle cell for example uses different parts of the DNA than a skin cell, which causes different genes to become active in each cell. What genes are turned “on” and “off” in a cell – the gene expression – determines the traits of the cell. Gene regulation To activate a gene, the DNA of that gene needs to be read and copied, which is called transcription. The resulting copy of the DNA is called RNA. The RNA can be used to produce proteins through a process called translation. Transcription and translation together enable a gene to come to expression. During his PhD, Sonneveld studied the regulation of gene expression, also called gene regulation. Innovative methods “I’ve actually worked on three different projects,” he says. “First, I have looked at the function of the so-called Argonaute protein in cells. This type of protein can detect and break down RNA molecules. Together with my colleagues, I have investigated how it does that.” To that end, the researchers used new, innovative methods, among which a technique that allowed them to study molecules under a microscope live. Breakdown of RNA Sonneveld also studied the cell cycle. During this process, a cell prepares itself for division, which results in two new daughter cells. “We discovered that the number of RNA molecules of a few genes drastically declines right after cell division and that the cell is responsible for the breakdown of these molecules. We don’t yet know how and why this happens.” Finally, he and his colleagues worked on the development of a new model and analysis with which specific parts of a gene can be visualized live. With his thesis, Sonneveld increases the understanding of gene expression and -regulation. That is not only important to gain better insights into the functioning of the human body, but also helps us understand what goes wrong in diseases such as cancer and Alzheimer’s. Highlights “Publishing our article was a real milestone. To see it finished after so many years of hard work feels very rewarding,” says Sonneveld. “I have really enjoyed my PhD. I liked doing research, especially the data analysis. And it is great that you get the opportunity and freedom to do lots of different things.” He would advise everyone who wants to start a PhD to find a place where they feel comfortable. “Even when your research is not going so well, you will still be happy to go there.” Stijn Sonneveld has started an IT traineeship to retrain as a data analyst.