Gi-Coupled GPCR Signaling Is Required at Multiple Levels and In Different Lineages In Hematopoiesis.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2635-2635
Author(s):  
Marie Terpager ◽  
Hiroshi Kataoka ◽  
Ivo Cornelissen ◽  
Shaun R. Coughlin
Keyword(s):  
Bone Marrow ◽  
Fetal Liver ◽  
Flow Cytometric Analysis ◽  
Liver Cells ◽  
Dependent Manner ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Fetal Liver Cells ◽  
Multiple Levels

Abstract Abstract 2635 G protein-coupled receptors (GPCRs) can regulate cell migration, survival, proliferation and differentiation –– key processes in hematopoiesis. The Gi-coupled receptor CXCR4 plays a key role in hematopoiesis, suggesting that related receptors might also contribute. Because all Gi family members except Gz are inhibited by pertussis toxin (PTX), we utilized a ROSA26-CreOnPTX mouse line that expresses PTX in a Cre-dependent manner to broadly probe the role of Gi signaling in hematopoiesis. Mice hemizygous for the hematopoietic lineage-specific Cre transgene Vav-iCre were crossed with ROSA26-CreOnPTX/CreOnPTX mice to generate offspring expressing PTX in hematopoietic lineages (Vav-PTX) and Cre-negative controls in which the PTX allele remained silent. Vav-PTX mice were born at the expected Mendelian rate, and except for a smaller thymus, were grossly normal, but all died with pneumonia between days 2 and 14. Bone marrow in 3 day-old Vav-PTX mice was hypocellular with significant underrepresentation of granulocytic and lymphocytic lineages as well as hematopoietic stem and progenitor cells (lin-, c-kit+, Sca1+). In bone marrow reconstitution studies, cells from Vav-PTX fetal livers (E14.5) showed impaired short-term and no long-term repopulating activity. Additionally, Vav-PTX fetal liver cells were significantly impaired in their ability to form granulocyte/macrophage and erythroid colonies in vitro. Interestingly, when wild-type E14.5 fetal liver cells were grown in vitro in presence of exogenous PTX, only erythroid colony formation was impaired, and flow cytometric analysis of the progenitor populations of Vav-PTX fetal liver revealed a significant decrease in granulocyte-macrophage progenitors (GMPs) as well as in common myeloid progenitors (CMPs) but not in megakaryocyte/erythroid progenitors (MEPs). Thus, reduced progenitor populations may account for reduced granulocyte/macrophage colony-forming activity in fetal liver cell cultures but does not account for reduced erythroid colony-forming activity. Indeed, normal MEP numbers in Vav-PTX livers and the ability of exogenous PTX to inhibit formation of erythroid colonies in wild-type fetal liver cultures suggests that Gi signaling in MEPs or their progeny may contribute to erythropoiesis in fetal liver. Several of the necessary roles of Gi signaling identified above are not accounted for by the function of CXCR4, and, taken together, our data suggest that Gi-coupled GPCRs likely contribute to hematopoiesis at multiple levels and in different lineages. An effort to identify GPCRs that contribute to erythropoiesis is underway. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Bclaf1 Promotes Maintenance and Self-Renewal of Fetal Hematopoietic Stem Cells

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1269-1269 ◽  
Author(s):  
Lynn S. White ◽  
Deepti Soodgupta ◽  
Rachel L. Johnston ◽  
Jeffrey A. Magee ◽  
Jeffrey J. Bednarski
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Fetal Liver ◽  
Liver Cells ◽  
Lower Percentage ◽  
Wild Type ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Fetal Liver Cells

Abstract Hematopoietic stem cells (HSC) persist throughout life by undergoing extensive self-renewal divisions while maintaining an undifferentiated state. The mechanisms that support HSC self-renewal change throughout the course of development as temporal changes in transcriptional regulators coordinate distinct genetic programs in fetal, post-natal and adult HSCs. These self-renewal programs are often ectopically activated in leukemia cells to drive neoplastic proliferation and high expression of HSC-associated genes predicts a poor prognosis in acute myelogenous leukemia (AML). In this regard, it was recently shown that expression of the transcriptional regulator BCLAF1 (Bcl2 associated transcription factor 1) is increased in AML blasts relative to normal precursor populations and suppression of BCLAF1 causes reduced proliferation and induction of differentiation to a dendritic cell fate. These findings raise the question of whether BCLAF1 may regulate normal as well as neoplastic self-renewal programs. We find that Bclaf1 is highly expressed in HSCs versus committed bone marrow populations consistent with a potential role for this gene in HSC functions. To test whether BCLAF1 regulates HSC development and hematopoiesis, we used germline loss of function mice. Bclaf1-/- mice succumb to pulmonary failure shortly after birth due to poor lung development, so we assessed prenatal hematopoiesis. Bclaf1-deficient mice had significantly reduced HSC and hematopoietic progenitor cell (HPC) frequencies and numbers despite normal fetal liver cellularity. To determine if Bclaf1 is required for HSC function during fetal development, we performed competitive reconstitution assays. Fetal liver cells from Bclaf1+/+or Bclaf1-/-mice were transplanted along with wild-type competitor bone marrow cells into lethally irradiated recipient mice. Compared to recipients of Bclaf1+/+fetal liver cells, recipients of Bclaf1-/-cells had a significantly lower percentage of donor-derived leukocytes at all time points after transplantation as well as reduced percentage of donor HSCs at 16 weeks post-transplant. Notably, all leukocyte populations (B cells, T cells, granulocytes and macrophages) from Bclaf1-/-donors were reduced consistent with an abnormality in HSC repopulating activity rather than a defect in a specific differentiation pathway. Consistent with these findings, Bclaf-deficient cells did not engraft in competitive transplants with limiting numbers of sorted fetal liver HSCs whereas sorted wild-type Bclaf1+/+cells effectively reconstituted hematopoiesis in recipient mice. In addition, Vav-cre:Bclaf1flox/floxmice, which have selective deletion of Bclaf1 in hematopoietic cells, have reduced frequencies and numbers of fetal liver HSCs identical to the findings observed in germline Bclaf1-/-mice. These results show that loss of Bclaf1 leads to defective development and repopulating activity of fetal HSCs. Interestingly, when adult mice are successfully engrafted with Bclaf1-deficient HSCs, the donor HSCs suffer no additional functional impairment. Furthermore, in secondary transplant experiments Bclaf1-deficient HSCs maintain long-term repopulating activity. Thus, Bclaf1 may have distinct functions in fetal versus adult HSC self-renewal. Collectively, our findings reveal Bclaf1 is a novel regulator of fetal HSC function and suggest that it may have distinct functions in different developmental contexts. Disclosures No relevant conflicts of interest to declare.

Roles of Histone Acetyltransferase MORF and MOZ in Hematopoiesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2525-2525
Author(s):  
Takuo Katsumoto ◽  
Issay Kitabayashi
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Liver Cells ◽  
Wild Type ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Fetal Liver Cells

Abstract Abstract 2525 Poster Board II-502 MOZ (MOnocytic leukemia Zinc finger protein) and MORF (MOz Related Factor), Myst-type histone acetyltransferases, are involved in chromosome translocations associated with FAB-M4/5 subtypes of acute myeloid leukemia. We have reported that MOZ is essential for hematopoietic cell development and self-renewal of hematopoietic stem cells. To explore the possibility MORF also plays important roles in hematopoiesis, we generated Morf-deficient mice with homologous recombination methods. Morf−/− mice were smaller than their wildtype littermates and died within 4 weeks after birth on C57BL/6 background. In MORF−/− fetal liver, Flt3-negative KSL (c-Kit+ Sca-1+ Lineage-) cells containing hematopoietic stem cells were decreased. When fetal liver cells were transplanted into irradiated recipient mice, MORF−/− cells less efficiently reconstituted hematopoiesis than wild-type cells. Additionally, bone marrow cells reconstituted with MORF−/− cells rarely contributed to hematopoiesis in secondary transplants. To reveal relationship between MORF and MOZ in hematopoiesis, we generated double heterozygous (Moz+/− Morf+/−) mouse. Double heterozygous mice were smaller than wild-type littermates and died at least 4 weeks after birth. Numbers of KSL cells, especially Flt3- KSL cells and common myeloid progenitors were decreased in the double heterozygous embryos. The double heterozygous fetal liver cells also displayed less activity to reconstitute hematopoiesis than MOZ+/− or MORF+/− cells. Since MORF−/− mice and MOZ/MORF double heterozygous mice were alive at adult on a mixed C57BL/6/DBA2 genetic background, we investigated adult hematopoiesis in these mice. MORF−/− or MOZ/MORF double heterozygous mice were smaller than their wild-type littermates and had small numbers of thymocytes and splenocytes. However, there were no significant differences in number of bone marrow cells and hematopoietic lineage population in MORF−/− or MOZ/MORF double heterozygous mice. These results suggest that MORF as well as MOZ plays important roles in self-renewal of hematopoietic stem cells. Disclosures: No relevant conflicts of interest to declare.

Impaired Repopulating Activity of Fus-Deficient Hematopoietic Stem Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2222-2222
Author(s):  
Takeaki Sugawara ◽  
Atsushi Iwama
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Fetal Liver ◽  
Chromosomal Translocation ◽  
Liver Cells ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Significant Difference ◽  
Fetal Liver Cells

Abstract RNA-binding protein FUS (also known as TLS) was originally identified in chromosomal translocation in human myxoid liposarcoma. The FUS gene is also translocated with the transcription factor gene ERG in human myeloid leukemia with recurrent chromosomal translocation t(16;21). Multiple data suggest that wild-type FUS is also involved in the development of leukemia as one of the downstream targets for oncoproteins including BCR-ABL. However, little is known about the role of FUS in the normal hematopoiesis. The previous report demonstrated that Fus-deficient (Fus−/−) newborn mice, which die shortly after birth because they cannot suckle, have a non-cell-autonomous defect in B lymphocyte development. No cell-autonomous defect of Fus−/− hematopoietic cells has been documented. Here we report the detailed analyses of the Fus−/− fetal liver hematopoietic stem cells (HSCs). Fus−/− fetal livers at embryonic day 14.5 were smaller in size and exhibited a significant reduction in hematopoietic cell numbers by 60% compared with the wild type (WT). Nonetheless, no significant difference was observed in the proportion of stem/progenitor cell fraction (lineage-marker-c-Kit+Sca-1+; KSL) as well as colony-forming cells between WT and Fus−/− fetal livers. Fus−/− KSL cells proliferated and differentiated almost normally in vitro. To examine in vivo repopulating activity, we transplanted fetal liver cells to lethally irradiated CD45.1 recipients with competitor bone marrow cells. Fus−/− fetal liver donor cells reconstituted recipients’ hematopoiesis for the long term and contributed to all cell lineages including B lymphocytes. In contrast to the in vitro results, however, the chimerism of donor-derived cells was significantly lower in recipients receiving Fus−/− fetal liver cells compared with WT controls (approximately 2-fold reduction). This trend was reproducible with both unfractionated and purified KSL fetal liver test cells. Our data demonstrated that the proto-oncogene Fus is involved in the maintenance of normal HSC functions. Detailed analyses on the underlying mechanisms are in progress.

Transdifferentiation of Bone Marrow-Derived Cells Co-Cultured with Fetal Liver Cells into Hepatic-Like Cells without Fusion.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 4176-4176
Author(s):  
Yasuhiro Yamada ◽  
Yuji Yonemura ◽  
Eishi Nishimoto ◽  
Hiroaki Mitsuya
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Liver Cells ◽  
Cytokeratin 19 ◽  
Rt Pcr ◽  
Hematopoietic Stem ◽  
Bone Marrow Derived Cells ◽  
Fetal Liver Cells

Abstract Several research groups have reported that bone marrow cells (BMCs) transdifferentiate into hepatocytes in rodents. However, it is yet to be studied what factors effectively trigger and sustain the transdifferentiation of BMCs to hepatocytes. In the present study, we investigated whether murine BMCs in the presence of fetal liver cells (FLCs) could differentiate into hepatic-like cells in vitro without fusion. Fractionated BMCs from C57Bl/6-TgN(ACTbEGFP)10bs mice and FLCs from B6.129S7-Gt(ROSA)26Sor mice were co-cultured at 1x105 cells and 1x106 cells in 10% FCS-containing medium supplemented with hepatocyte growth factor on laminin-coated dishes. Hepatocyte-specific markers among BMCs were detected as assessed by immunocytochemistry for albumin and reverse transcription-polymerase chain reaction (RT-PCR) for alpha-fetoprotein (AFP), albumin, and cytokeratin-19 mRNAs. We also found that Sca-1+ BMCs containing both hematopoietic stem cells and AFP-expressing cells could differentiate into hepatic-like cells and such cells were seen adherent to dish together with FLCs in the early phase of culture. Moreover, the AFP-expressing cells were found in a Sca-1+ cKit- cell fraction, which also differentiated into CD45− GFP+ albumin+ cells and proved to be positive for GFP but negative for LacZ as assessed by RT-PCR and immunocytochemistry. These results suggest that albumin+ cells developed through transdifferentiation from BMCs but not through spontaneous cell fusion between BMCs and FLCs.

Basis of hematopoietic defects in platelet-derived growth factor (PDGF)-B and PDGF β-receptor null mice

Blood ◽  
2001 ◽  
Vol 97 (7) ◽  
pp. 1990-1998 ◽  
Author(s):  
Wolfgang E. Kaminski ◽  
Per Lindahl ◽  
Nancy L. Lin ◽  
Virginia C. Broudy ◽  
Jeffrey R. Crosby ◽  
...  
Keyword(s):  
Growth Factor ◽  
Fetal Liver ◽  
Liver Cells ◽  
Platelet Derived Growth Factor ◽  
Wild Type ◽  
Liver Growth ◽  
Hematologic Disorders ◽  
Fetal Liver Cells ◽  
Β Receptor

Abstract Platelet-derived growth factor (PDGF)-B and PDGF β-receptor (PDGFRβ) deficiency in mice is embryonic lethal and results in cardiovascular, renal, placental, and hematologic disorders. The hematologic disorders are described, and a correlation with hepatic hypocellularity is demonstrated. To explore possible causes, the colony-forming activity of fetal liver cells in vitro was assessed, and hematopoietic chimeras were demonstrated by the transplantation of mutant fetal liver cells into lethally irradiated recipients. It was found that mutant colony formation is equivalent to that of wild-type controls. Hematopoietic chimeras reconstituted with PDGF-B−/−, PDGFRβ−/−, or wild-type fetal liver cells show complete engraftment (greater than 98%) with donor granulocytes, monocytes, B cells, and T cells and display none of the cardiovascular or hematologic abnormalities seen in mutants. In mouse embryos, PDGF-B is expressed by vascular endothelial cells and megakaryocytes. After birth, expression is seen in macrophages and neurons. This study demonstrates that hematopoietic PDGF-B or PDGFRβ expression is not required for hematopoiesis or integrity of the cardiovascular system. It is argued that metabolic stress arising from mutant defects in the placenta, heart, or blood vessels may lead to impaired liver growth and decreased production of blood cells. The chimera models in this study will serve as valuable tools to test the role of PDGF in inflammatory and immune responses.

The Rho Family GTPase Cdc42 Regulates Multiple Hematopoietic Stem/Progenitor Cell Functions and Erythropoiesis.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 32-32
Author(s):  
Lei Wang ◽  
Linda Yang ◽  
Marie–Dominique Filippi ◽  
David A. Williams ◽  
Yi Zheng
Keyword(s):  
Bone Marrow ◽  
Fetal Liver ◽  
Brdu Incorporation ◽  
Low Density ◽  
Actin Assembly ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Rho Family

Abstract The Rho family GTPase Cdc42 has emerged as a key signal transducer in cell regulation. To investigate its physiologic function in hematopoiesis, we have generated mice carrying a gene targeted null allele of cdc42gap, a major negative regulatory gene of Cdc42 and mice with conditional targeted cdc42 allele (cdc42flox/flox). Deletion of the respective gene products in mice was confirmed by PCR genotyping and Western blotting. Low-density fetal liver or bone marrow cells from Cdc42GAP−/− mice displayed ~3 fold elevated Cdc42 activity and normal RhoA, Rac1 or Rac2 activity, indicating that cdc42gap deletion has a specific effect on Cdc42 activity. The Cdc42GAP-deficient hematopoietic stem/progenitor cells (HSC/Ps, Lin−c-Kit+) generated from Cdc42GAP−/− E14.5 fetal liver and the Cdc42−/− HSC/Ps derived by in vitro expression of Cre via a retrovirus vector from Cdc42flox/flox low density bone marrow showed a growth defect in liquid culture that was associated with increased apoptosis but normal cell cycle progression. Cdc42GAP-deficient HSC/Ps displayed impaired cortical F-actin assembly with extended actin protrusions upon exposure to SDF–1 in vitro and a punctuated actin structure after SCF stimulation while Cdc42−/− but not wild type HSC/Ps responded to SDF-1 in inducing membrane protrusions. Both Cdc42−/− and Cdc42GAP−/− HSC/Ps were markedly decreased in adhesion to fibronectin. Moreover, both Cdc42−/− and Cdc42GAP−/− HSC/Ps showed impaired migration in response to SDF-1. These results demonstrate that Cdc42 regulation is essential for multiple HSC/P functions. To understand the in vivo hematopoietic function of Cdc42, we have characterized the Cdc42GAP−/− mice further. The embryos and newborns of homozygous showed a ~30% reduction in hematopoietic organ (i.e. liver, bone marrow, thymus and spleen) cellularity, consistent with the reduced sizes of the animals. This was attributed to the increased spontaneous apoptosis associated with elevated Cdc42/JNK/Bid activities but not to a proliferative defect as revealed by in vivo TUNEL and BrdU incorporation assays. ~80% of Cdc42GAP−/− mice died one week after birth, and the surviving pups attained adulthood but were anemic. Whereas Cdc42GAP−/− mice contained small reduction in the frequency of HSC markers and normal CFU-G, CFU-M, and CFU-GM activities, the frequency of BFU-E and CFU-E were significantly reduced. These results suggest an important role of Cdc42 in erythropoiesis in vivo. Taken together, we propose that Cdc42 is essential for multiple HSC/P functions including survival, actin cytoskeleton regulation, adhesion and migration, and that deregulation of its activity can have a significant impact on erythropoiesis. Cdc42 regulates HSC/P functions and erythropoiesis Genotype/phenotype Apoptosis increase Adhesion decrease Migration decrease F-actin assembly HSC frequency decrease BFU-E, CFU-E decrease The numbers were indicated as fold difference compared with wild type. ND:not determined yet. Cdc42GAP−/− 2.43, p<0.005 0.97, p<0.01 1.01, p<0.01 protrusion (SDF-1); punctruated (SCF) 0.34, p<0.05 0.92, p<0.01; 0.38, p<0 Cdc42−/− 3.68, p<0.005 0.98, p<0.001 3.85, p<0.005 protrusion (SDF-1) ND ND

Roles of MOZ in Hematopoiesis.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2269-2269
Author(s):  
Takuo Katsumoto ◽  
Yukiko Aikawa ◽  
Takahiro Ochiya ◽  
Issay Kitabayashi
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Fetal Liver ◽  
Liver Cells ◽  
Recipient Mouse ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Homozygous Mutant ◽  
Fetal Liver Cells ◽  
Acute Myeloid

Abstract The AML1-CBFβ transcription factor complex is the most frequent target of specific chromosome translocations in acute myeloid leukemia (AML). The monocytic leukemia zinc finger (MOZ) gene, which encodes a MYST-type histone acetyltransferase (HAT), is also involved in leukemia-associated translocations such as t(8;16), t(8;22) and inv(8), which are associated with acute myeloid leukemia with M4/5 subtypes. We previously found that MOZ functions as a potent coactivator for AML1. To investigate roles of MOZ in normal hematopoiesis, we generated MOZ-deficient mice using gene-targeting method. MOZ homozygous mutant is embryonic lethal and it died between days 14 and 15 of gestation. In fetal liver of MOZ-deficient E14.5 embryos, the total cell numbers and the colony-forming cells (CFCs) in a methylcellulose medium were remarkably reduced when compared with wild-type littermates. Flow cytometry analysis indicated that hematopoietic stem cells (HSCs) and progenitors of both myeloid and lymphoid lineages were severely reduced in MOZ-deficient embryos. Especially, the levels of c-kit expression were strongly reduced in lineage-negative cells. Differentiation arrest of erythroid progenitors at a terminal stage and increase in the numbers of Mac-1 and Gr-1 positive cells suggest that MOZ also plays roles in cell differentiation of erythroid, monocytic and granulocytic lineages. In E12.5 MOZ deficient fetal liver cells, expression profile analysis revealed decreases in expressions of thrombopoietin receptor c-mpl, Wnt related ligand dkk2 and HoxA9 and increase in HoxA5 expression. To further determine roles of MOZ in HSCs functions and their progenitors differentiation ability, competitive reconstitution assays were performed. Ly5.2+ fetal liver cells from wild-type, heterozygous or homozygous mutant embryos together with Ly5.1+ competitor fetal liver cells were transplanted into γ-irradiated Ly5.1+/Ly5.2+ recipient mouse. Ly5.2+ wild-type cells were observed in recipient mice after transplantation. However, cells derived from MOZ homozygous mutant embryos were not detected in peripheral blood, bone marrow, spleen and thymus. Reduced population of cells derived from heterozygous mutant embryos were observed. These data suggest that MOZ is required for lymphoid and myeloid development and for self-renewal of HSCs.

Long-Term Cell Autonomous Effect of Tet2 Loss in Hematopoietic Cells in Mice.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2416-2416
Author(s):  
Tomoya Muto ◽  
Goro Sashida ◽  
Motohiko Oshima ◽  
Chiaki Nakaseko ◽  
Kotaro Yokote ◽  
...  
Keyword(s):  
Fetal Liver ◽  
Hematopoietic Cells ◽  
Extramedullary Hematopoiesis ◽  
Liver Cells ◽  
Severe Anemia ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Myeloid Malignancies ◽  
Fetal Liver Cells

Abstract Abstract 2416 TET2 mutations are frequently observed in myeloid malignancies including myelodysplastic syndrome (MDS), myeloproliferative neoplasm (MPN) and MDS/MPN. Several groups have already reported that deletion of Tet2 in mice leads to dysregulated hematopoietic stem cell self-renewal and subsequent development of myeloid malignancies. Of note, mice hypomorphic or heterozygous for the Tet2 allele have been reported to show similar phenotypes as those of Tet2-null mice, suggesting that haploinsufficiency of Tet2 plays a role in the development of myeloid malignancies. However, little is known about long-term cell autonomous effects of Tet2 loss in hematopoietic cells: most of the reports were based on relatively short-term observations or did not exclude the influence of Tet2 loss in the niche cells. To study long-term cell autonomous effect of Tet2 loss in hematopoietic cells, we analyzed the hematopoiesis of wild-type recipient mice reconstituted with fetal liver cells from Tet2 hypomorphic mice for a longer period up to 1 year. Tet2 gene trap mice (Tet2trap/trap), in which the gene trap vector was inserted into the exon 2 of Tet2 just before the first coding exon, express Tet2 mRNA at the level approximately 20% of that of the wild-type (WT) mice (Shide et al. Leukemia 2012). We transplanted fetal liver cells from E14.5 WT or Tet2trap/trap mice into lethally irradiated recipient mice. At 4 months after transplantation, the recipient mice reconstituted with Tet2trap/trap cells showed a significantly increased proportion of monocytes in peripheral blood (PB) compared with those with WT cells (WT=5.59±2.57%, Tet2trap/trap=12.67±7.45%, p=0.01). While there were no significant differences between the two groups in the bone marrow (BM) compartments including the numbers of Lineage−Sca-1+c-Kit+ (LSK) hematopoietic stem/progenitor cells, extramedullary hematopoiesis in the spleen was markedly enhanced in the recipients with Tet2trap/trap cells. The proportion of LSK, granulocyte/macrophage progenitors (GMPs) and megakaryocyte/erythroid progenitors (MEPs) in the spleen of recipient mice reconstituted with WT and Tet2trap/trap cells were 0.002±0.001% vs 0.006±0.001% (p<0.01), 0.007±0.004% vs 0.029±0.01% (p=0.026) and 0.084±0.024% vs 0.25±0.044% (p<0.01), respectively. These findings were compatible with those reported previously and indicated that recipient mice reconstituted with Tet2trap/trapcells induce chronic myelomonocytic leukemia (CMML)-like disease. Of note, after a long observation period, particularly after 9 months post-transplantation, mice reconstituted with Tet2trap/trap cells developed advanced hematological disease and 53.3% (8 of 15) died or were killed because of their moribund condition by 11 months after transplantation. Detailed analysis on moribund as well as surviving mice reconstituted with Tet2trap/trap cells (n=3 each) revealed that the 2/3 of the mice developed CMML-like disease with monocytosis in PB and evident extramedullary hematopoiesis harboring increased number of LSK and GMPs in spleen, whereas the remaining 1/3 of mice developed MDS/MPN-like disease with severe anemia. The latter mice did not show monocytosis in PB and BM, but displayed dyserythropoiesis accompanied by massive extramedullary erythropoiesis, as we saw increased number of LSK and MEPs, but not GMPs, in spleen. The proportion of Annexin V+ cells in Ter119highCD71higherythroblasts in the BM of WT mice, CMML-like disease-carrying mice and MDS/MPN-like disease-carrying mice were 9.46±0.53%, 10.71±0.36%, and 19.04±0%, respectively, suggesting that the enhanced apoptosis led to the severe anemia seen in the MDS/MPN-like disease-carrying mice. Thus, decreased expression of Tet2 is sufficient to promote not only CMML-like disease, but also an MDS/MPN-like disease as well. Our findings confirmed a long-term cell autonomous effect from insufficient function of Tet2 in the development of hematological diseases. Interested in the molecular mechanism of disease progression, we have identified 1,642 differentially methylated regions (DMRs) in Tet2trap/trap GMPs compared with WT GMPs by ChIP-sequencing. We are now working to understand how these DMRs are involved in the development of the two distinct diseases associated with hypomorphic Tet2. Disclosures: No relevant conflicts of interest to declare.

The Erythropoietin Receptor Regulates The Number Of Cell Divisions and The Duration Of Erythroblast Terminal Differentiation By Regulating Erythroblast Iron

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 428-428
Author(s):  
Daniel Hidalgo ◽  
Ramona Pop ◽  
Prem Ponka ◽  
Merav Socolovsky
Keyword(s):  
Multispectral Imaging ◽  
Fetal Liver ◽  
Flow Cytometric Analysis ◽  
Terminal Differentiation ◽  
Liver Cells ◽  
S Phase ◽  
Erythropoietin Receptor ◽  
Cell Divisions ◽  
Fetal Liver Cells

Abstract Signaling by the erythropoietin receptor (EpoR) is essential for the survival of definitive colony-forming unit-erythroid (CFU-e) progenitors and their erythroblast progeny. Here we used EpoR-null embryos to ask whether EpoR signaling might also exert essential non-survival functions in erythropoiesis. To address this, we rescued EpoR-null fetal liver cells from death by transducing them in vitro with either the anti-apoptotic protein Bcl-xL, or, as control, with the wild-type EpoR. The Bcl-xL-transduced EpoR-null cells survived, expressed hemoglobin and underwent morphological erythroid maturation and enucleation. However, unlike exogenous EpoR, exogenous Bcl-xL was unable to support the formation of EpoR-null CFU-e colonies in methylcellulose. The absence of colonies was explained by the finding that the Bcl-xL-transduced progenitors underwent fewer cell divisions than equivalent EpoR-transduced cells (1.1 vs. 2.9 in 24 hr, respectively) and had a slower rate of intra-S phase DNA synthesis, suggesting longer S phase duration. Multispectral imaging showed that the Bcl-xL-transduced cells matured prematurely, attaining smaller cell and nuclear size and a lower nuclear/cytoplasmic ratio at earlier time points than EpoR-transduced cells. Premature maturation was also evident by flow cytometric analysis. Thus, EpoR-null fetal liver cells in vivo arrest in their differentiation at the transition from subset S0 (Ter119-neg CD71-low) to S1 (Ter119-neg CD71-high) (Pop et al, PLoS Biology 2010). Rescue with EpoR in vitro allows EpoR-null progenitors to resume differentiation, sequentially upregulating CD71 and Ter119. By contrast, rescue of EpoR-null cells with Bcl-xL results in their premature upregulation of Ter119 and failure to upregulate CD71 to high levels. The cell cycle and differentiation deficits in Bcl-xL-supported, EpoR-null erythropoiesis were associated with a slower loss of DNA methylation from the erythroid genome, and with slower erythroid gene transcription. CD71 (the transferrin receptor) is a known target of EpoR and Stat5 signaling. We asked whether the deficits of EpoR-null erythropoiesis might be the result of low cell surface CD71 and the consequent reduced iron transport. In support of this hypothesis, we found that EpoR-null fetal liver cells that are transduced with both CD71 and Bcl-xL resume the normal maturation rate characteristic of EpoR-supported differentiation, as judged by multispectral imaging measurements of cell size and nuclear/cytoplasmic ratio. Further, we were able to restore rapid S phase to Bcl-xL-transduced EpoR-/- erythroblasts by culturing them in the presence of the cell-permeant iron chelator Fe-SIH (salicylaldehyde isonicotinoyl hydrazone), which is able to supply the cell interior with iron even in the absence of CD71 (Figure 1). We suggest that EpoR-mediated upregulation of CD71 at the onset of erythroid terminal differentiation determines the number and duration of erythroblast cell divisions by regulating iron homeostasis. Disclosures: No relevant conflicts of interest to declare.

Sign in / Sign up

Export Citation Format

Share Document