On January 1, 2025, Marissa Gredler officially joined MCB as an Assistant Professor. Her journey into the world of science began in a place familiar to many—uncertainty. Growing up in Florida, she, like many aspiring scientists, initially thought her path would lead to medical school. “Growing up with two parents in medicine, and my own interests in math and science, I always planned to go to medical school,” Gredler says. However, during her undergraduate studies, a pivotal encounter with an inspiring professor shifted her trajectory. “I had one incredible professor who made it absolutely clear that research was not only interesting but beautiful and important,” she says. This revelation led her to cancel her scheduled MCAT exam and embrace a new passion for research.
Gredler’s academic journey kept her in Florida for both undergraduate and graduate school at the University of Florida, where she began delving into the intricacies of urethral development in Martin Cohn’s lab. “Urethral tubulogenesis is an important problem in and of itself, but also relevant for understanding fundamental cell behaviors, genetic interactions, and evolutionary events,” she explains. Gredler used transgenic mice to identify processes that control mammalian urethral formation and then asked what these same genes and processes do in reptilian external genital development. Her work on this topic not only provided insights into a common birth defect in humans but also broadened her understanding of cell behavior and evolutionary biology. “Combining classical mouse genetics with comparative approaches identifies key behaviors by which cells build tissues,” she says. “Learning this in graduate school was a formative lesson in the power of tackling scientific questions from many different angles.”
Live Imaging of Mouse Embryos
This early work set the stage for Gredler’s postdoctoral studies at Memorial Sloan Kettering Institute in New York, where she joined the lab of renowned developmental biologist Jen Zallen, who has contributed key discoveries to developmental biology using live imaging to investigate cell behaviors in fly embryos. In joining the Zallen lab, Gredler’s expertise in mouse embryogenesis allowed them to embark on an ambitious project to apply live imaging methods to the problem of cell behaviors in mouse development.
This project involved imaging intact, living mouse embryos at cellular and sub-cellular resolution—an endeavor that had traditionally been nearly impossible. The work was groundbreaking, and Gredler’s role in developing this live imaging system became the foundation for her future research.
Gredler’s research focuses on understanding how cells transition from one state to another, particularly during epithelial-mesenchymal transition (EMT) and its reverse (MET), both of which are crucial in development and disease. “My work is about following small groups or neighborhoods of cells and understanding how they exhibit core modules of behavior,” she explains. One of her key findings involves the identification of a structure known as a multicellular rosette, which plays a critical role in linking these transitions. “Cells collectively migrate before joining with their neighbors to form multicellular rosettes, which are 3D, spherical cysts with internal lumens. Those cysts then expand and fuse together as they essentially pop onto the embryo surface to form a single epithelium, like bubbles at the surface of water” she elaborates. This discovery, she notes, provides new insights into the fundamental mechanisms of tissue formation.
After innovating techniques to study cell behaviors in live mouse embryos, Gredler’s next steps were to apply these methods to new questions. Seeking to understand how cell behaviors fit into the broader context of cell fate, she spent a year working at the National Cancer Institute in the lab of Terry Yamaguchi, an expert in signaling and stem cells in mouse embryos. As a member of MCB, she is continuing a journey of uncovering cell behaviors in embryonic development. Because she images intact, living mouse embryos, this method allows her to observe how cells move, interact, and form tissues in real time, providing unprecedented insights into the dynamic processes that drive development.
The Gredler Lab at MCB
“Marissa’s elegant work is uncovering how the choreography of cells of the embryo drives the generation of shape and form,” adds Sharad Ramanathan, Llura and Gordon Gund Professor of Neuroscience and of Molecular and Cellular Biology. “Learning through careful observation is the path to understanding nature and Marissa is on such a path.”
Gredler’s enthusiasm for her work matches her excitement about joining the Harvard community. She was drawn to MCB because of its scientific diversity and its focus on molecular and cell biology—fields that are central to her research. “MCB is incredibly scientifically diverse, yet it all rotates around an axis of curiosity,” she says. The collaborative environment and the opportunity to work alongside experts in various related fields made Harvard the ideal place for her to establish her lab.
Gredler’s new colleagues strongly agree. “Marissa Gredler is a trailblazer in the field of developmental biology, and she will be a shot in the arm for our department, which has sought to strengthen itself in this centrally important field,” says Richard Losick, Maria Moors Cabot Research Professor of Biology. “She brings cutting-edge microscopy to bear on questions of how tissues and organs assemble during embryogenesis in mammals.”
MCB Chair Rachelle Gaudet adds, “I’m delighted to welcome Marissa into our department! Marissa’s beautiful discovery of dynamic multicellular rosette assemblies in the early organization of the embryo set the stage for her exciting research program in early development in mammals. Marissa’s research interests at the intersection of cell and developmental biology will reinvigorate our research and teaching in that area, and her program will synergize with our existing strength in biological imaging. Marissa also has expertise and interests in evolution, another field for which there are many opportunities for fruitful interactions in MCB and in the greater life sciences community at Harvard.”
Teaching and Mentorship Remains an Important Focus
Beyond her research, Gredler is deeply committed to teaching and mentoring. Inspired by the mentors who guided her own career, she looks forward to fostering the next generation of scientists at Harvard. “I chose to pursue a career in science because I had an inspiring teacher and mentor who illustrated the importance of rigor, integrity, scholarship, and maintaining an open mind in science, and I aspire to embody those ideals in my own lab and classroom,” she says. Gredler is particularly enthusiastic about developing a course in developmental biology.
Gredler’s journey is not just about science. Outside the lab, she is a food and wine enthusiast and enjoys playing tennis, practicing yoga, and spending time with her dogs. She enjoys living in Boston, both for the vibrant academic environment and the opportunities to explore a new city.
Building a Lab and Recruiting Talent
In her new role at Harvard, Gredler is actively recruiting for her lab. She is excited to build a team that will explore the developmental processes that have fascinated her for years. “Mentoring trainees at all levels—undergrads, graduate students, postdocs—is extremely important to me,” she says. “It’s the way to push things forward in a way that I could never do by myself.”
Gredler’s arrival at Harvard marks the beginning of an exciting new chapter in her career. Her innovative research and passion for mentorship promise to make a significant impact on the field of developmental biology and the broader scientific community at Harvard. As she continues to unravel the mysteries of embryonic development, she will undoubtedly inspire and guide the next generation of scientists, just as her mentors once inspired her.
She says, “One of the reasons why I am especially enthusiastic about joining MCB is that a number of pioneering developmental biologists have walked the Biolabs halls, doing foundational work in our field. It is an honor to join the ranks of such incredible scientists and teachers. ”
