Project description:Umbilical cord blood (CB) is a non-invasive, convenient and broadly used source of hematopoietic stem cells (HSCs) for allogeneic stem cell transplantation. However, limiting numbers of HSCs remain a major constraint for its clinical application. One feasible option would be to expand HSCs to improve therapeutic outcome, however available protocols and the molecular mechanisms governing the self-renewal of HSC are unclear. Here we show that ectopic expression of a single miRNA, miR-125a, in purified murine and human multipotent progenitors (MPP) resulted in increased self-renewal and robust long-term multi-lineage repopulation in transplanted recipient mice. Using quantitative proteomics and Western blot analysis, we identified a restricted set of miR-125a targets which revealed the involvement of the MAP kinase signaling pathway in conferring long-term repopulating capacity to multipotent progenitors in human and mice. Our findings offer the innovative potential to use MPP with enhanced self-renewal activity to augment limited sources of HSC to improve clinical protocols.
Project description:Epigenetic modifications must underlie lineage-specific differentiation since terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Hematopoiesis provides a well-defined model of progressive differentiation in which to study the role of epigenetic modifications in cell fate decisions. Multi-potent progenitors (MPPs) can differentiate into all blood cell lineages, while downstream progenitors commit to either myeloerythroid or lymphoid lineages. While DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs {Broske, 2009 #6}, a comprehensive DNA methylation map of hematopoietic progenitors, or of any cell lineage, does not exist. Here we have generated a mouse DNA methylation map, examining 4.6 million CpG sites throughout the genome including all CpG islands and shores, examining MPPs, all lymphoid progenitors (ALPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Interestingly, differentiation towards the myeloid lineage corresponds with a net decrease in DNA methylation, while lymphoid commitment involves a net increase in DNA methylation, but both show substantial dynamic changes consistent with epigenetic plasticity during development. By comparing lineage-specific DNA methylation to gene expression array data, we find many examples of genes and pathways not previously known to be involved in lymphoid/myeloid differentiation, such as Gcnt2, Arl4c, Gadd45α, and Jdp2. Several transcription factors, including Meis1 and Prdm16 were methylated and silenced during differentiation, suggesting a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome appears to be important in hematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation, often correlating with gene expression changes, and define a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions. mRNA expression of 8 hematopoietic progenitor populations [MPPFL-(5), MPPFL+(3), CMP(3), GMP(3), CLP(3), DN1(3), DN2(3), DN3(3)] were compared
Project description:Epigenetic modifications must underlie lineage-specific differentiation since terminally differentiated cells express tissue-specific genes, but their DNA sequence is unchanged. Hematopoiesis provides a well-defined model of progressive differentiation in which to study the role of epigenetic modifications in cell fate decisions. Multi-potent progenitors (MPPs) can differentiate into all blood cell lineages, while downstream progenitors commit to either myeloerythroid or lymphoid lineages. While DNA methylation is critical for myeloid versus lymphoid differentiation, as demonstrated by the myeloerythroid bias in Dnmt1 hypomorphs {Broske, 2009 #6}, a comprehensive DNA methylation map of hematopoietic progenitors, or of any cell lineage, does not exist. Here we have generated a mouse DNA methylation map, examining 4.6 million CpG sites throughout the genome including all CpG islands and shores, examining MPPs, all lymphoid progenitors (ALPs), common myeloid progenitors (CMPs), granulocyte/macrophage progenitors (GMPs), and thymocyte progenitors (DN1, DN2, DN3). Interestingly, differentiation towards the myeloid lineage corresponds with a net decrease in DNA methylation, while lymphoid commitment involves a net increase in DNA methylation, but both show substantial dynamic changes consistent with epigenetic plasticity during development. By comparing lineage-specific DNA methylation to gene expression array data, we find many examples of genes and pathways not previously known to be involved in lymphoid/myeloid differentiation, such as Gcnt2, Arl4c, Gadd45α, and Jdp2. Several transcription factors, including Meis1 and Prdm16 were methylated and silenced during differentiation, suggesting a role in maintaining an undifferentiated state. Additionally, epigenetic modification of modifiers of the epigenome appears to be important in hematopoietic differentiation. Our results directly demonstrate that modulation of DNA methylation occurs during lineage-specific differentiation, often correlating with gene expression changes, and define a comprehensive map of the methylation and transcriptional changes that accompany myeloid versus lymphoid fate decisions.
Project description:Gene expression analyses of Tif1b, Hp1a or Hp1g knockdown hematopoietic progenitors. Growth of hematopoietic stem cells (HSCs) are significantly impaired upon knockdown of Hp1a and Hp1g. Results provide insight into the role of these factors in hematopoiesis. HSCs (CD34- c-Kit+ Sca1+ Lineage- ) were transduced with lentivirus expressing shRNA against Tif1b, Hp1a or Hp1g, and cultured for 14 days. Then, GFP+ c-Kit+ Lineage- hematopoietic progenitors were sorted and subjected into microarray analysis
Project description:Infections are associated with extensive consumption of blood platelets representing a high risk for health. How the hematopoietic system coordinates the rapid and efficient regeneration of this particular lineage during such stress scenarios remains unclear. Here we report that the phenotypic hematopoietic stem cell (HSC) compartment contains highly potent megakaryocyte-committed progenitors (hipMkPs), a cell population that shares many features with multipotent HSCs and serves as a lineage-restricted emergency pool for inflammatory insults. Our data show that during homeostasis, hipMkPs are maintained in a primed but quiescent state, thus contributing little to steady-state megakaryopoiesis. Moreover, homeostatic hipMkPs show expression of megakaryocyte lineage priming transcripts for which protein synthesis is suppressed. We demonstrate that acute inflammatory signaling instructs activation of hipMkPs, as well as Mk protein production from pre-existing transcripts and drives a rapid maturation of hipMkPs and other Mk progenitors. This results in an efficient regeneration of platelets that are lost during inflammatory insult. Thus, our study reveals an elegant emergency machinery that counteracts life-threating depletions in the platelet pool during acute inflammation.