ABSTRACT: Hematopoietic stem cells (HSCs) are defined by their capacity to regenerate all main components of the peripheral blood, but individual HSCs exhibit a range of preferences for generating downstream cell types. Their propensities are thought to be epigenetically encoded, but no differential regulatory mechanisms have been identified. Here, we considered whether DNA methyltransferase 3A (DNMT3A) has a role in determining the differentiation choice of HSCs. We find that the most primitive megakaryocyte-biased HSCs depend most on DNMT3A for efficient hematopoietic regeneration, particularly of the lymphoid lineages. Reduced DNMT3A amplifies the biased HSC behavior. DNMT3A also regulates megakaryocyte and platelet output in part through DNA methylation at key megakaryocyte lineage loci. Together, our findings establish the role of epigenetic regulation in the fate of megakaryocyte-biased HSCs and their downstream progeny and suggest that the outcomes of DNMT3A-mutant clonal hematopoiesis and malignancies might vary depending on the identity of the HSC that acquires the mutation.
Project description:Hematopoietic stem cells (HSCs) are defined by their capacity to regenerate all main components of the peripheral blood, but individual HSCs exhibit a range of preferences for generating downstream cell types. Their propensities are thought to be epigenetically encoded, but no differential regulatory mechanisms have been identified. Here, we considered whether DNA methyltransferase 3A (DNMT3A) has a role in determining the differentiation choice of HSCs. We find that the most primitive megakaryocyte-biased HSCs depend most on DNMT3A for efficient hematopoietic regeneration, particularly of the lymphoid lineages. Reduced DNMT3A amplifies the biased HSC behavior. DNMT3A also regulates megakaryocyte and platelet output in part through DNA methylation at key megakaryocyte lineage loci. Together, our findings establish the role of epigenetic regulation in the fate of megakaryocyte-biased HSCs and their downstream progeny and suggest that the outcomes of DNMT3A-mutant clonal hematopoiesis and malignancies might vary depending on the identity of the HSC that acquires the mutation.
Project description:Hematopoietic stem cells (HSCs) are defined by their capacity to regenerate all main components of the peripheral blood, but individual HSCs exhibit a range of preferences for generating downstream cell types. Their propensities are thought to be epigenetically encoded, but no differential regulatory mechanisms have been identified. Here, we considered whether DNA methyltransferase 3A (DNMT3A) has a role in determining the differentiation choice of HSCs. We find that the most primitive megakaryocyte-biased HSCs depend most on DNMT3A for efficient hematopoietic regeneration, particularly of the lymphoid lineages. Reduced DNMT3A amplifies the biased HSC behavior. DNMT3A also regulates megakaryocyte and platelet output in part through DNA methylation at key megakaryocyte lineage loci. Together, our findings establish the role of epigenetic regulation in the fate of megakaryocyte-biased HSCs and their downstream progeny and suggest that the outcomes of DNMT3A-mutant clonal hematopoiesis and malignancies might vary depending on the identity of the HSC that acquires the mutation.
Project description:Hematopoietic stem cells (HSCs) are defined by their capacity to regenerate all main components of the peripheral blood, but individual HSCs exhibit a range of preferences for generating downstream cell types. Their propensities are thought to be epigenetically encoded, but no differential regulatory mechanisms have been identified. Here, we considered whether DNA methyltransferase 3A (DNMT3A) has a role in determining the differentiation choice of HSCs. We find that the most primitive megakaryocyte-biased HSCs depend most on DNMT3A for efficient hematopoietic regeneration, particularly of the lymphoid lineages. Reduced DNMT3A amplifies the biased HSC behavior. DNMT3A also regulates megakaryocyte and platelet output in part through DNA methylation at key megakaryocyte lineage loci. Together, our findings establish the role of epigenetic regulation in the fate of megakaryocyte-biased HSCs and their downstream progeny and suggest that the outcomes of DNMT3A-mutant clonal hematopoiesis and malignancies might vary depending on the identity of the HSC that acquires the mutation.
Project description:The hematopoietic stem cell (HSC) compartment is heterogeneous, yet our understanding of the identities of different HSC subtypes is limited. Here we show that platelet integrin CD41 (M-NM-1IIb), currently thought to only transiently mark fetal HSCs, is expressed on an adult HSC subtype that accumulates with age. CD41+ HSCs were largely quiescent and exhibited myeloerythroid and megakaryocyte gene priming, governed by Gata1, whereas CD41- HSCs were more proliferative and exhibited lymphoid gene priming. When isolated without the use of blocking antibodies, CD41+ HSCs possessed long-term repopulation capacity upon serial transplantations and showed a marked myeloid-bias compared to CD41-HSCs, which yielded a more lymphoid-biased progeny. CD41-knockout mice displayed multilineage hematopoietic defects coupled with decreased quiescence and survival of HSCs, suggesting that CD41 is functionally relevant for HSC maintenance and hematopoietic homeostasis. Transplantation experiments indicated that CD41-KO associated defects are long-term transplantable and HSC-derived, and in part mediated through the loss of platelet mass leading to decreases in HSC exposure to important platelet released cytokines, such as TGFM-NM-21. In summary, our data provide a novel marker to identify a myeloid-biased HSC subtype that becomes prevalent with age, and highlights the dogma of HSC regulation by their progeny. For microarray analysis, 1000 HSCs were FACS sorted from pools of 4-5 mice directly into lysis buffer, RNA extracted and whole transcript amplification was performed as previously described (Gonzalez-Roca E, Garcia-Albeniz X, Rodriguez-Mulero S, Gomis RR, Kornacker K, Auer H. Accurate expression profiling of very small cell populations. PLoS One. 2010;5:e14418.)
Project description:The traditional view of hematopoiesis has been that all the cells of the peripheral blood are the progeny of a unitary homogeneous pool of hematopoietic stem cells (HSCs). Recent evidence suggests that the hematopoietic system is actually maintained by a consortium of HSC subtypes with distinct functional characteristics. We show here that myeloid-biased HSCs (My-HSCs) and lymphoid-biased (Ly-HSCs) can be purified according to their capacity for Hoechst dye efflux in combination with canonical HSC markers. We used microarray expression profiling to determine the transcriptional profiles of myeloid-biased lower-SP HSCs and lymphoid-biased upper-SP HSCs Three biological replicates were analyzed for each HSC subpopulation. Lower-SP and upper-SP HSCs were purified from three pools of mice on separate days. HSCs were further purified with the addition of canonical HSC makers; Sca-1+ c-Kit+ Lineage-
Project description:Increasing evidence links metabolic activity and cell growth to decline in hematopoietic stem cell (HSC) function during aging. The Lin28b/Hmga2 pathway controls tissue development and in the hematopoietic system the postnatal downregulation of this pathway causes a decrease in self renewal of adult HSCs compared to fetal HSCs. Igf2bp2 is an RNA binding protein and a mediator of the Lin28b/Hmga2 pathway, which regulates metabolism and growth signaling by influencing RNA stability and translation of its target genes. It is currently unknown whether Lin28/Hmga2/Igf2bp2 signaling impacts on aging-associated impairments in HSC function and hematopoiesis. Here, we analyzed homozygous Igf2bp2 germline knockout mice and wildtype control animals to address this question. The study shows that Igf2bp2 deletion rescues aging phenotypes of the hematopoietic system, such as the expansion of HSC numbers in bone marrow and the biased increase of myeloid cells in peripheral blood. This rescue of hematopoietic aging coincides with reduced mitochondrial metabolism and glycolysis in Igf2bp2-/- HSCs compared to Igf2bp2+/+ HSCs. Conversely, Igf2bp2 overexpression activates protein synthesis pathways in HSCs and leads to a rapid loss of self renewal by enhancing myeloid skewed differentiation in an mTOR/PI3K-dependent manner. Together, these results show that Igf2bp2 regulates energy metabolism and growth signaling in HSCs and that the activity of this pathways influences self renewal, differentiation, and aging of HSCs.