Epigenetic drivers of stem cell fitness in aging hematopoiesis - Project Summary Stem cell dysfunction is a hallmark of aging tissues, and often results in the clonal expansion of stem cells carrying somatic mutations that enhance their fitness. In the hematopoietic system, over 75% of individuals aged 70 and older have hematopoietic stem cells (HSCs) carrying leukemia-associated somatic mutations, a phenomenon known as clonal hematopoiesis (CH). The rise in CH coincides with increased chronic inflammation, which I have recently shown drives the expansion of TP53-mutant stem cells. Similarly, HSCs carrying TET2 mutations, which disrupt the removal of DNA methylation marks, preferentially expand under inflammatory conditions. However, the precise mechanisms by which methylation changes drive TET2-mutant stem cell fitness in response to age-associated inflammation remain poorly understood, preventing the development of interventions to halt clonal expansions and their deleterious health consequences. Using a new human in-vitro model of CH I have developed, this proposal aims to elucidate how disrupted DNA methylation drives the defective inflammatory response of TET2-KO cells under chronic IL6 treatment, and might ultimately contribute to their enhanced fitness,. The specific aims are to (1) determine how DNA methylation controls inflammatory gene expression in TET2-KO HSCs, by defining and manipulating cis-regulatory regions that govern their transcription, (2) characterize epigenetic clones that preferentially expand under chronic inflammation using a new high-throughput single-cell methylation technology, and (3) address the causal role of DNA methylation driving HSC fitness by targeted DNA methylation editing. Aim 1 and part of Aim 2 will be carried out during the training phase (K99), whilst parts of Aim 2 and all of Aim 3 will be completed in the independent phase (R00). Overall, this proposal will reveal fundamental molecular mechanisms shaping stem cell fitness in aging and pave the way for designing interventions that promote healthy aging and extend healthspan. The comprehensive training plan proposed will provide specialized knowledge and leadership skills necessary for a successful transition to independence. The training will focus on three key areas: aging biology, computational analysis of single-cell methylation data, and management of a research group. This training will take place within the exceptional scientific ecosystem of Dana-Farber Cancer Institute, the Broad Institute and Harvard Medical School, which offer extensive collaborative opportunities and cutting-edge resources in epigenetics and aging research. Under the exceptional mentorship of Prof. Bernstein, who has a strong track record of trainees securing independent faculty positions, I will develop crucial skills in research leadership, manuscript preparation, and grant writing, while also benefiting from his guidance in establishing professional connections and navigating the faculty position search and interview process. This will be complemented with excellent guidance from an expert Research Advisory Committee, which will uniquely position me to launch a competitive and innovative research program in epigenetic stem cell aging at a top biomedical research institute.
