Recent large exome sequencing studies in humans have shown that aging is inevitably associated with an increased frequency of somatic mutations in the hematopoietic system, which provide a competitive growth advantage to the mutant cell and thus allows for its clonal expansion (clonal hematopoiesis). While these somatic mutations increase the risk of future blood cancer, unexpectedly they have also been associated with a higher incidence of cardiovascular conditions, such as ischemic stroke, suggesting a previously unrecognized connection between somatic mutations in hematopoietic cells and cardiovascular disease. In these studies, it was identified that the two most commonly mutated genes in elderly individuals were DNMT3A and TET2, which are epigenetic regulators that play key roles in hematopoiesis and immune function. Indeed, recent experimental studies by the sponsors laboratory have revealed that hematopoietic mutations in these genes play a causal role in accelerating atherosclerosis and/or heart failure by promoting inflammation. However, it is unknown as to whether these mutations may augment the pathogenesis of other inflammation-driven cardiovascular conditions, such as ischemic stroke whereby the mechanisms of injury differ. This project aims to test whether somatic mutations in Tet2 (aim 1) and/or Dnmt3a (aim 2) within hematopoietic cells will worsen stroke outcome by exacerbating inflammation driven brain injury. To achieve these aims, competitive bone marrow transplantation and adoptive transfer strategies will be used to model TET2 or DNMT3A mutation-driven clonal hematopoiesis. Following transplant with mutant cells, stroke will be induced in mice by occluding the middle cerebral artery with a monofilament. Functional outcomes and infarct volumes will be evaluated either acutely (3 d) or over a time-course of 14 d. To uncover the potential mechanisms by which these mutations may promote post-stroke brain injury, we will examine post-stroke inflammation at acute timepoints (1 and 3 d) after stroke. If successful, this study will provide mouse genetic evidence supporting a causal connection between somatic TET2 and/or DNMT3A mutations in blood cells and poor outcome following stroke in humans. Further, they will provide mechanistic insight into the cellular processes affected by these mutations, which could lead to the design of personalized therapies and/or preventative strategies for individuals carrying mutations in this gene.
|Program type||Postdoctoral Fellowship|
|Effective start/end date||01/01/2020 → 12/31/2021|