Project description:The Core Binding Factor (CBF) protein RUNX1 is a master regulator of definitive hematopoiesis, crucial for hematopoietic stem cell (HSC) emergence during ontogeny, which also plays vital roles in adult mice, in regulating the correct specification of numerous blood lineages. Akin to the other mammalian Runx genes, Runx1 has two promoters P1 (distal) and P2 (proximal) which generate distinct protein isoforms. The activities and specific relevance of these two promoters in adult hematopoiesis remain to be fully elucidated. Utilizing a dual reporter model we demonstrate here that the distal P1 promoter is broadly active in adult hematopoietic stem and progenitor cell (HSPC) populations. By contrast the activity of the proximal P2 promoter is more restricted and its upregulation, in both the immature Lineage- Sca1high cKithigh (LSK) and bipotential Pre-Megakaryocytic/Erythroid Progenitor (PreMegE) populations, coincides with a loss of erythroid specification. Accordingly the PreMegE population can be prospectively separated into âpro-erythroidâ and âpro-megakaryocyteâ populations based on Runx1 P2 activity. Comparative gene expression analyses between Runx1 P2+ and P2- populations indicated that the level of CD34 expression could substitute for P2 activity to distinguish these two cell populations in wild type (WT) bone marrow (BM). Prospective isolation of these two populations will provide the opportunity to further investigate and define the molecular mechanisms involved in megakaryocytic/erythroid (Mk/Ery) cell fate decisions. mRNA profiles of wild type (WT), Runx1 P2-hCD4+ (P2+) and Runx1 P2-hCD4- (P2-) Bone marrow Pre-Megakryocyte/Erythroid (PreMegE) progenitors were generated from young adult (12-16 weeks) mice by deep sequencing, in triplicate, using Illumina NextSeq 500.
Project description:Cellular binary fate decisions require the progeny to silence genes associated with the alternative fate. The major subsets of alpha:beta T cells have been extensively studied as a model system for fate decisions. While the transcription factor RUNX3 is required for the initiation of Cd4 silencing in CD8 T cell progenitors, it is not required to maintain the silencing of Cd4 and other helper T lineage genes. The other runt domain containing protein, RUNX1, silences Cd4 in an earlier T cell progenitor, but this silencing is reversed whereas the gene silencing after RUNX3 expression is not reverse. Therefore, we hypothesized that RUNX3 and not RUNX1 recruits other factors that maintains the silencing of helper T lineage genes in CD8 T cells. To this end, we performed a proteomics screen of RUNX1 and RUNX3 to determine candidate silencing factors.
Project description:The Core Binding Factor (CBF) protein RUNX1 is a master regulator of definitive hematopoiesis, crucial for hematopoietic stem cell (HSC) emergence during ontogeny, which also plays vital roles in adult mice, in regulating the correct specification of numerous blood lineages. Akin to the other mammalian Runx genes, Runx1 has two promoters P1 (distal) and P2 (proximal) which generate distinct protein isoforms. The activities and specific relevance of these two promoters in adult hematopoiesis remain to be fully elucidated. Utilizing a dual reporter model, we demonstrate here that the distal P1 promoter is broadly active in adult hematopoietic stem and progenitor cell (HSPC) populations. By contrast, the activity of the proximal P2 promoter is more restricted and its upregulation, in both the immature Lineage- Sca1high cKithigh (LSK) and bipotential Pre-Megakaryocytic/Erythroid Progenitor (PreMegE) populations, coincides with a loss of erythroid specification. Accordingly, the PreMegE population can be prospectively separated into "pro-erythroid" and "pro-megakaryocyte" populations based on Runx1 P2 activity. Comparative gene expression analyses between Runx1 P2+ and P2- populations indicated that the level of CD34 expression could substitute for P2 activity to distinguish these two cell populations in wild type (WT) bone marrow (BM). Prospective isolation of these two populations will provide the opportunity to further investigate and define the molecular mechanisms involved in megakaryocytic/erythroid (Mk/Ery) cell fate decisions. Moreover, comparison of a RUNX1C null (KO) PreMegE to its WT counterpart demonstrated considerably enhanced erythroid specification at the expense of megakaryopoiesis in the absence of P1-specified RUNX1C expression.
Project description:Adult hematopoiesis has been studied in terms of progenitor differentiation potentials, whereas its kinetics in vivo is poorly understood. We combined inducible lineage tracing of endogenous adult hematopoietic stem cells (HSC) with flow cytometry and single-cell RNA sequencing to characterize early steps of hematopoietic differentiation in the steady state. Labeled cells, comprising primarily long-term HSC and some short-term HSC, produced megakaryocytic lineage progeny within one week, in a process that required only 2-3 cell divisions. Erythroid and myeloid progeny emerged simultaneously by 2 weeks, and included a progenitor population with expression features of both lineages. Myeloid progenitors at this stage showed diversification into granulocytic, monocytic and dendritic cell types, and rare intermediate cell states could be detected. In contrast, lymphoid differentiation was virtually absent within the first 3 weeks of tracing. These results show that continuous differentiation of HSC rapidly produces major hematopoietic lineages and cell types, and reveal fundamental kinetic differences between megakaryocytic, erythroid, myeloid and lymphoid differentiation.
Project description:MEIS1 is a transcription factor expressed in hematopoietic stem and progenitor cells (HSPC) and in mature megakaryocytes. In contrast to its role in leukemogenesis, the role of MEIS1 in normal hematopoiesis is largely unknown. We show that MEIS1 can direct human hematopoietic progenitors towards a megakaryocyte-erythroid progenitor (MEP) fate. Ectopoic expression of MEIS1 in CD34+ cells resulted in increased erythroid differentiation at the expense of granulocyte and monocyte (GM) differentiation. MEIS1 overexpression not only skewed differentiation of CMPs towards the erythroid lineage but also reprogrammed GM progenitors towards erythrocyte differentiation. Expression profiling was used to determine the transcriptional changes induced by MEIS1 that lead to the oberved phenotype. A transcriptional program enriched for erythrocytic and megakaryocytic genes was detected.
Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other
Project description:Growth Factor Independence-1B (Gfi-1B) is a transcriptional repressor essential for erythropoiesis and megakaryopoiesis. Targeted gene disruption of Gfi-1B in mice leads to embryonic lethality due to failure to produce definitive erythrocytes, hindering the study of Gfi-1B function in adult hematopoiesis. We here show that, in humans, Gfi-1B controls the development of erythrocytes and megakaryocytes by regulating the proliferation and differentiation of bipotent erythro-megakaryocytic progenitors (MEP). We further identify in this cell population the type III transforming growth factor-? receptor gene, TGFBR3, as a direct target of Gfi-1B. Knock down of Gfi-1B results in altered TGF? signaling as shown by the increase in Smad2 phosphorylation and its inability to associate to the Transcription Intermediary Factor 1? (TIF1?). Because Smad2/TIF1? complex is known to specifically regulate erythroid differentiation, we propose that, by repressing the transforming growth factor-? receptor III (T?R?II) expression, Gfi-1B favors the Smad2/TIF1? interaction downstream of TGF? signaling, allowing immature progenitors to differentiate toward the erythroid lineage.