At the beginning of March, FIMM was happy to welcome our newest Group Leader Mikko Myllymäki, MD, PhD. His research sits at the intersection of clinical hematology, genomics, and immunology, focusing on how genetic alterations that arise in blood stem cells during ageing influence human health and disease.
By combining population-scale genetic data with experimental models and clinical insight, Myllymäki aims to uncover how these molecular changes affect immune function and disease risk, and how such knowledge could eventually translate into improved care for patients.
A scientist shaped by the north
Myllymäki’s scientific journey began in Northern Finland. Born and raised in Lapland, he developed a passion for biomedical research during his first year of medical school in Oulu. A lecture on cellular responses to oxygen deprivation sparked his curiosity about the molecular mechanisms that allow human cells to adapt to environmental stress.
That early interest led him into laboratory research during medical school and eventually into the field of hematopoiesis, the process by which blood cells are formed.
What struck me early on was how quickly discoveries from preclinical research can be translated into novel therapies in hematology. It is fair to say that medical training has really shaped my research career and vice versa.
Over the years, mentors and international collaborations helped shape his approach to translational research. During his PhD studies, a period spent working with Professor Josef Prchal in Salt Lake City, Utah, demonstrated how clinical practice and laboratory science can be closely integrated. Later, his postdoctoral training at Dana-Farber Cancer Institute and Harvard Medical School under Professor Coleman Lindsley further refined this approach.
After returning to Finland, Myllymäki continued to develop his research career with the support of Professor Satu Mustjoki, while specialising in clinical hematology in Helsinki. He established his own research group in 2022 at the Faculty of Medicine. Today, his team includes PhD students and Master’s students with both computational and experimental expertise, and he plans to expand further as the group settles into its new environment at FIMM.
What ageing blood cells can reveal about disease risk
At the centre of the group’s research is a phenomenon known as clonal hematopoiesis. As people age, cells throughout the body accumulate genetic alterations. In blood stem cells in the bone marrow, some of these alterations allow certain cell clones to expand. This process is increasingly recognised as an important feature of human ageing.
Although clonal hematopoiesis increases the risk of developing blood cancers, the majority of individuals carrying these genetic changes will never develop malignancy. Yet research over the past decade has revealed that these same mutations can influence immune cell function and may contribute to a wide range of inflammatory diseases associated with ageing.
Understanding this broader biological impact is a major goal of Myllymäki’s research.
By elucidating the full spectrum of biological and clinical implications of clonal hematopoiesis, our results may yield novel preventative and treatment options for inflammatory diseases and cancer that continue to pose a significant burden of morbidity and mortality in the aging populations.
One area that particularly excites his team involves large-scale chromosomal alterations that occur in blood stem cells. While many studies have focused on individual gene mutations, changes affecting entire chromosomal regions can alter the activity of hundreds of genes simultaneously.
Using population-scale datasets such as FinnGen, Myllymäki’s group has identified specific chromosomal alterations that appear to influence the risk of age-related inflammatory diseases. The next step is to understand how these alterations affect immune cell behaviour at the molecular level.
“We are incredibly excited to test how chromosomal alterations impact immune cell function using cutting-edge genomic engineering and single-cell multiomic approaches on cell lines and patient samples to discover the functional consequences of clonal hematopoiesis in human health.”
To tackle these questions, the team combines computational and experimental approaches. Bioinformatic analyses identify individuals with clonal hematopoiesis across large genetic datasets. In parallel, laboratory experiments use genome editing tools such as CRISPR and stem cell models to recreate these genetic changes and study their biological consequences.
“Close collaboration between wet-lab and computational team members is essential for successful execution of our projects.”
Towards clinical applications
For Myllymäki, the ultimate goal is to translate these discoveries into clinical applications. As a practising hematology fellow, he sees first-hand how many patients still struggle with serious blood diseases despite recent therapeutic advances.
Seeing the struggles of our hematologic malignancy patients really serves as a humbling reminder that there is still a lot to learn before we can permanently cure every patient.
In the future, he hopes that deeper biological understanding of clonal hematopoiesis could improve how clinicians predict disease risk and tailor treatments. Genetic alterations associated with clonal hematopoiesis may one day serve as biomarkers guiding therapy choices in both blood cancers and solid tumours.
Beyond cancer, the research could also have implications for the ageing population more broadly. Some scientists believe that targeting inflammatory processes driven by clonal hematopoiesis may help reduce the burden of age-related diseases.
“In the bigger picture, I hope that through our translational research we can help the general elderly population to live longer and live better.”
Joining FIMM provides a natural environment for pursuing these ambitions. The institute’s strong expertise in genomics, computational biology and population data offers opportunities to explore new hypotheses generated by large genetic studies.
“The groundbreaking work of FIMM researchers in identifying genotype–phenotype associations will serve as the basis for huge numbers of biological hypotheses that we hope to explore.”
Myllymäki also sees an important role for physician-scientists in bridging different disciplines within biomedical research.
“Close collaboration between clinicians, biologists and computational scientists is necessary for making progress in biomedical research, and learning together is the best part of doing science.”
Beyond the lab: community, mentorship and inspiration
Alongside his research, Myllymäki remains active in the clinical community. He chairs the Finnish MDS group and serves on the board of the Nordic MDS group, organisations dedicated to improving care and advancing research in myelodysplastic syndromes. He is also involved in international efforts through the European Hematology Association.
These networks support clinical trials, guideline development and collaboration between researchers and clinicians across countries.
Within his own laboratory, mentorship and intellectual curiosity are central values. Myllymäki encourages students to pursue ideas independently while emphasising rigorous scientific thinking and open discussion.
Up to 60 to 80 per cent of research is about troubleshooting failed experiments. I hope my students have a low threshold for discussing the next steps in their projects with me.
Outside the laboratory and clinic, he enjoys spending time with his family and staying active through running, cycling and tennis. Even these moments often circle back to science.
“Listening to hematology-related podcasts while running is a great way for me to relax and think creatively about new research ideas.”
As he begins this new chapter at FIMM, Myllymäki hopes not only to advance the understanding of clonal hematopoiesis but also to help inspire the next generation of physician-scientists.
“The physician scientist career is a dream come true for me. I am grateful for the opportunity to join FIMM and I hope to inspire young medical doctors who are interested in research.”