Introducing our <scp>Associate Editorial Board</scp> : An interview with <scp>Agathe Chaigne</scp> , <scp>Utrecht University</scp> , <scp>The Netherlands</scp>

I am generally interested in how cells divide. One thing that I find fascinating is that cells have more or less the same division machinery. However, different cell types in different organisms or tissues of your body divide in various ways. They use the same machinery slightly differently. Throughout my career, I have investigated various aspects of this. During my PhD, I focused on oocytes. Oocytes are intriguing because they undergo two asymmetric divisions, where one cell is enormous and the other two are tiny. Only the big cell becomes an oocyte and carries out a reproductive function. These cells divide asymmetrically without the typical machinery. Specifically, they lack astral microtubules. I've delved into understanding how the mechanical properties of the cells allow this unique division process. Later, I shifted my focus to stem cells, which are equally fascinating. Stem cells can differentiate into any cell type in an organism. In my work with mouse stem cells, I discovered that instead of separating immediately after cell division, these cells remain connected for an extended period (Figure 1). More broadly, in my lab, we explore the wide variety of the dynamics of cell division. Our model organisms include stem cells and choanoflagellates, which are unicellular eukaryotes that can form colonies if they remain connected after cell division. It is mostly coincidence, really—a series of decisions. Unlike those who knew their research interests from childhood, I made decisions without consciously aiming for this field. During my studies, I completed internships related to the cell cycle and cellular life. When I started my PhD, I joined a project in Paris that focused on peculiar cell divisions. I got hooked on the topic. Later, in London, I explored stem cells, drawn by the intersection of biophysics and cell division. I also chose labs where mentorship mattered—places where people were kind and had lives beyond science. It was essential for me to find mentors who valued work–life balance and family. That is how my journey unfolded. Many people have influenced me. I chose places to work based on both the research and the people. So, I guess I have taken a little bit from all of my previous mentors. But some of the most influential people have been my peers, in particular my fellow postdocs at UCL. They were a cohort of strong, smart, and driven people. Seeing them made me realize that I belonged among them, that maybe this job was something I could excel at. Overall, they were a fantastic group. Their mentoring really pushed me forward. I watch a lot of football—I am really into it. Right now, with the Euros, it is an exciting time. I also play fantasy football. Beyond that, I play ice hockey in a team. I will admit, I am absolutely terrible at it—I am very, very bad. But there is something intense about playing. When you are on the ice, there is no room for anything else in your brain. Disconnecting from our work can be challenging. I'm always thinking about things—whether it is mentoring people, tiny experimental details, or future grant proposals. Ice hockey provides a break; it is so intense that it is quite relaxing. Additionally, I have two young kids. My daughter just turned four today, and my son will be two in 3 weeks. So, they occupy most of my time. I do not know how to answer that, really. This might sound so French and pessimistic, but I have not been impressed by many people lately, which is a bit of a shame. I think it is also not a very good time for politics right now. So, I would say that overall, in that area, I have mostly been quite disillusioned. Mostly, I am influenced by people around me—my peer scientists, for example. They're doing an amazing job, persistently advancing science despite adversity and with often seldom recognition. That is what I find impressive. Agathe Chaigne I'm fascinated by cell division. It is a universal mechanism using very conserved machinery, yet every cell type performs its own little flavor using a subset of this machinery. I am interested in how cells exploit that universal process in different contexts, with a focus on development and cell mechanics. During my PhD in the Terret-Verlhac lab in Paris (2011–2015), I studied the role of actin-based mechanical properties in the spindle positioning, in the mouse oocyte and in early embryos. There, cells do not have centrosome and spindle positioning is all about actin (Bennabi et al., 2020; Chaigne et al., 2013, 2015, 2016). Then, in the Paluch lab in London (2015–2021), I investigated the division of embryonic stem cells. There, cells grow in 3D multicellular colonies and undergo dynamic fate transitions. I showed that 3D cell divisions are asymmetric in size without affecting cell fate (Chaigne et al., 2021) and that the dynamics of cell state transitions are controlled by a change in the speed of the last step of cell division, abscission (Chaigne et al., 2020). In my own lab, which opened in January 2022 at the Department of Cell Biology at Utrecht University, we use our expertise in early development, biophysics, cell division and long-term imaging to study how cell division and cell fate transitions crosstalk. In particular, I obtained an NWO Vidi in 2022 as well as a FEBS Excellence Award in 2023 to study in embryonic stem cells the molecular and mechanical regulation of cytoplasmic bridges (Kodba et al., 2024; Kodba & Chaigne, 2023), which are tubes of membrane connecting cells after division that need to be cut (Figure 1). More broadly, we are interested in the conservation of modulating cytokinetic speed across the tree of life, and its role in different cell types, for which I just received an ERC Starting Grant (Chaigne & Brunet, 2022).