Altered inflammatory response associated with acquired DNMT3A mutations

PROJECT SUMMARY The human gene DNMT3A encodes one of the three enzymes that carry out DNA methylation in humans. Clonal expansion of blood cells with acquired mutations in DNMT3A is common in older adults, occurring in 5-10 % of healthy individuals aged 60 or above. Carriers of DNMT3A mutations have an approximately tenfold increased risk of developing hematologic cancers and are twice as likely to develop coronary heart disease. Given the rapidly aging population in the United States and worldwide, understanding the mechanistic basis of the association between acquired DNMT3A mutations in blood cells and increased susceptibility to cancer and cardiovascular disease is tremendously important for public health. Recent studies found evidence of increased inflammation mediated by myeloid cells when the ortholog of DNMT3A was perturbed in animal models. However, the molecular mechanisms underlying this phenomenon and whether DNMT3A mutations affect the inflammatory response of human myeloid cells remain poorly understood. To address this gap in knowledge, we established an experimental system based on myeloid cells differentiated from human pluripotent stem cells. Using this system, we found that human macrophages with DNMT3A mutations displayed altered inflammatory response compared to wild-type macrophages, characterized by augmented expression of IL-6, a potent proinflammatory cytokine. The IL6 promoter was one of the most significantly hypomethylated loci in DNMT3A-mutated macrophages, suggesting a direct mechanistic link between DNA methylation and inflammatory response in our model. In this application, we propose to characterize the molecular signature of the inflammatory response associated with DNMT3A mutations using genetically defined human macrophages and neutrophils and to dissect the epigenetic mechanisms underlying DNMT3A-mediated gene expression regulation. In addition, we will examine the impact of harboring clonally expanded blood cells with DNMT3A mutations on the inflammatory response of primary myeloid cells using a novel single-cell transcriptomic technique. We are in an ideal position to pursue this project given the availability of human pluripotent stem cell-based human myeloid cell models that we have developed and validated, our access to a large biobank representing extremely diverse populations, and the assembly of a strong scientific team consisting of investigators with complementary expertise. Findings from the proposed study will provide critical new insights into the consequence of acquiring DNMT3A mutations on inflammation, and help us develop novel strategies to prevent and treat pathologic conditions related to DNMT3A mutations.