Targeting Metabolic Vulnerabilities to Restore Balanced Hematopoiesis during Aging

Project Summary/Abstract The blood system deteriorates with age with the function of hematopoietic stem and progenitor cells (HSPCs), specifically, declining. Frequently with age, driver mutations cause a smaller number of individual HSPCs, or clones, to contribute disproportionally to differentiated blood progeny leading to hematopoietic clonal dominance and increased rates of hematological malignancy and cardiovascular disease. This accumulation of somatic mutations is common among many aged tissues. Alteration in the metabolic state of aged HSPCs leading to impaired function is well documented however, metabolic heterogeneity among aged HSPCs has only recently been appreciated. Whether the metabolic heterogeneity of aged HSPCs is clone specific is unknown. The overarching hypothesis of this proposal is that hematopoietic clonal dominance in aging is caused by a divergent metabolic state and correction of this divergent metabolic state would restore hematopoietic function and decrease disease acquisition in older individuals. I have demonstrated that HSPC clonal imbalance occurs in zebrafish in the absence of known driver mutations, similar to humans, using a genetic barcoding strategy. Aim 1 of this proposal pairs single-cell metabolomics and genetic cellular barcoding to identify metabolic alterations in dominant HSPCs in the absence of known driver mutations during the K99 phase of this award. The second half of Aim 1, to be accomplished during the R00 phase is to interrogate the metabolic pathways that differentiate dominant from non-dominant HSPCs to identify therapeutic targets to prevent hematopoietic clonal imbalance with aging. Using a method of combining mosaic editing of genes frequently edited in HSPCs of older humans and colorimetric barcoding I have demonstrated that the choline pathway is perturbed in dominant HSPCs. Pharmacological inhibition of choline lipid species production was sufficient to reduce mutant HSPC clonal expansion. During the K99 phase of this award, I will determine the mechanism of this inhibitor to reduce clonal expansion by performing intracellular methylome profiling. In the R00 phase I will test the relevance of this pharmacological intervention in human HSPCs in a xenotransplantation setting. By understanding the metabolic state of dominant HSPC clones during onset and progression in non-mutant and mutant contexts, interventions can be designed and applied to prevent age-related declines of the hematopoietic system. I have developed training goals that will center on 1) expanding my single-cell analysis skillset, 2) developing my intracellular methylation experiment capabilities, 3) mastering human HSPC culture, 4) enhancing my scientific communication, 5) growing my biology of aging footprint, and 6) growing my mentorship and leadership skills. The research and training plan designed for this K99/R00 award will support my long-term career goal to become an independent investigator at a research-intensive institution studying how metabolism underlies the hematopoietic dysfunction seen in individuals as they age.