Abstract:The family of ten-eleven translocation dioxygenases (TETs) consists of TET1, TET2, and TET3. Although all TETs are expressed in hematopoietic tissues, only TET2 is commonly found to be mutated in age-related clonal hematopoiesis and hematopoietic malignancies. TET2 mutation causes abnormal epigenetic landscape changes and results in multiple stages of lineage commitment/differentiation defects as well as genetic instability in hematopoietic stem/progenitor cells (HSPCs). TET2 mutations are founder mutations (f… Show more
“…8f ), an oncometabolite that directly inhibits Tet dioxygenases 81 . Absence of Tet1 / Tet3 activity in combination with Tet2 KO was indeed reported to accelerate the leukemogenesis process 82 and their indirect inhibition by Sox4 may contribute to the highly increased epigenetic dysregulation observed in Sox4 OE Tet2 KO cells. Fig.…”
Hematopoietic stem cell (HSC) mutations can result in clonal hematopoiesis (CH) with heterogeneous clinical outcomes. Here, we investigate how the cell state preceding Tet2 mutation impacts the pre-malignant phenotype. Using an inducible system for clonal analysis of myeloid progenitors, we find that the epigenetic features of clones at similar differentiation status are highly heterogeneous and functionally respond differently to Tet2 mutation. Cell differentiation stage also influences Tet2 mutation response indicating that the cell of origin’s epigenome modulates clone-specific behaviors in CH. Molecular features associated with higher risk outcomes include Sox4 that sensitizes cells to Tet2 inactivation, inducing dedifferentiation, altered metabolism and increasing the in vivo clonal output of mutant cells, as confirmed in primary GMP and HSC models. Our findings validate the hypothesis that epigenetic features can predispose specific clones for dominance, explaining why identical genetic mutations can result in different phenotypes.
“…8f ), an oncometabolite that directly inhibits Tet dioxygenases 81 . Absence of Tet1 / Tet3 activity in combination with Tet2 KO was indeed reported to accelerate the leukemogenesis process 82 and their indirect inhibition by Sox4 may contribute to the highly increased epigenetic dysregulation observed in Sox4 OE Tet2 KO cells. Fig.…”
Hematopoietic stem cell (HSC) mutations can result in clonal hematopoiesis (CH) with heterogeneous clinical outcomes. Here, we investigate how the cell state preceding Tet2 mutation impacts the pre-malignant phenotype. Using an inducible system for clonal analysis of myeloid progenitors, we find that the epigenetic features of clones at similar differentiation status are highly heterogeneous and functionally respond differently to Tet2 mutation. Cell differentiation stage also influences Tet2 mutation response indicating that the cell of origin’s epigenome modulates clone-specific behaviors in CH. Molecular features associated with higher risk outcomes include Sox4 that sensitizes cells to Tet2 inactivation, inducing dedifferentiation, altered metabolism and increasing the in vivo clonal output of mutant cells, as confirmed in primary GMP and HSC models. Our findings validate the hypothesis that epigenetic features can predispose specific clones for dominance, explaining why identical genetic mutations can result in different phenotypes.
“…Intriguingly, among the most upregulated metabolites with Sox4 overexpression was Hydroxyglutaric acid (2HG) ( Fig.S6F ), an oncometabolite that directly inhibits Tet dioxygenases 77 . Absence of Tet1/Tet3 activity in combination with Tet2 KO was indeed reported to accelerate the leukemogenesis process 78 and their indirect inhibition by Sox4 may contribute to the highly increased epigenetic dysregulation observed in Sox4 OE Tet2 KO cells.…”
Hematopoietic stem cell mutations can result in clonal hematopoiesis (CH) but the clinical outcomes are heterogeneous. The nature of the founder mutation and secondary mutations likely drive emergent neoplastic disease. We investigated how the state of the cell of origin where the Tet2 mutation occurs affects susceptibility to that commonly occurring CH mutation. Here, we provide evidence that risk is written in the epigenome of the cell of origin. By characterizing cell states that underlie myeloid differentiation and linking this information to an inducible system to assess myeloid progenitor clones, we provide evidence that epigenetic markers of the cell where Tet2 mutation occurs stratifies clonal behaviors. Specifically, Sox4 fosters a global cell state of high sensitization towards Tet2 KO. Using GMP and primary HSC models, we show that Sox4 promotes cell dedifferentiation, alters cell metabolism and increases the in vivo clonal output of mutant cells. Our results validate the hypothesis that epigenetic features can predispose specific clones for dominance and explain why an identical mutation can result in different outcomes.
“…Data indicate that TET enzymes regulate the function of embryonic stem cells by maintaining pluripotency and cell fate during development by regulating differentiation [ 29 ]. Under physiological conditions, deregulation of the TET enzymes mostly affects stem cells, blood cells, and cells associated with reproduction [ 30 , 31 ]. Notably, epigenetic drift involving aging-associated changes in 5-hydroxymethylation is an inseparable element of growing old.…”
Ten-eleven translocation (TET) enzymes catalyze the oxidation of 5-methylcytosine (5mC), first to 5-hydroxymethylcytosine (5hmC), then to 5-formylcytosine (5fC), and finally to 5-carboxycytosine (5caC). Evidence suggests that changes in TET expression may impact cell function and the phenotype of aging. Proliferation, apoptosis, markers of autophagy and double-strand DNA break repair, and the expression of Fibulin 5 were assessed by flow cytometry in TET1 and TET2-overexpressing fibroblasts isolated from sun-unexposed skin of young (23–35 years) and age-advanced (75–94 years) individuals. In cells derived from young individuals, TET1 overexpression resulted in the inhibition of proliferation and apoptosis by 37% (p = 0.03) and 24% (p = 0.05), respectively, while the overexpression of TET2 caused a decrease in proliferation by 46% (p = 0.01). Notably, in cells obtained from age-advanced individuals, TETs exhibited different effects. Specifically, TET1 inhibited proliferation and expression of autophagy marker Beclin 1 by 45% (p = 0.05) and 28% (p = 0.048), respectively, while increasing the level of γH2AX, a marker of double-strand DNA breaks necessary for initiating the repair process, by 19% (p = 0.04). TET2 inhibited proliferation by 64% (p = 0.053) and increased the level of γH2AX and Fibulin 5 by 46% (p = 0.007) and 29% (p = 0.04), respectively. These patterns of TET1 and TET2 effects suggest their involvement in regulating various fibroblast functions and that some of their biological actions depend on the donor’s age.
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