Browsing by keyword "*Hematopoiesis"

Now showing items 1-3 of 3

    • Definitive hematopoiesis requires Runx1 C-terminal-mediated subnuclear targeting and transactivation
      Dowdy, Christopher R.; Xie, Ronglin; Frederick, Dana; Hussain, Sadiq; Zaidi, Sayyed K.; Vradii, Diana; Javed, Amjad; Li, Xiangen; Jones, Stephen N.; Lian, Jane B.; et al. (2010-03-15)
      Runx1 is a key hematopoietic transcription factor required for definitive hematopoiesis and is a frequent target of leukemia-related chromosomal translocations. The resulting fusion proteins, while retaining DNA binding activity, display loss of subnuclear targeting and associated transactivation functions encoded by the C-terminus of the protein. To define the precise contribution of the Runx1 C-terminus in development and leukemia, we created a knock-in mouse with a C-terminal truncation by introducing a single nucleic acid substitution in the native Runx1 locus. This mutation (Runx1(Q307X)) models genetic lesions observed in patients with leukemia and myeloproliferative disorders. The Runx1(Q307X) homozygous mouse exhibits embryonic lethality at E12.5 due to central nervous system hemorrhages and a complete lack of hematopoietic stem cell function. While able to bind DNA, Runx1(Q307X) is unable to activate target genes, resulting in deregulation of various hematopoietic markers. Thus, we demonstrate that the subnuclear targeting and transcriptional regulatory activities of the Runx1 C-terminus are critical for hematopoietic development. We propose that compromising the C-terminal functions of Runx1 is a common mechanism for the pathological consequences of a variety of somatic mutations and Runx1-related leukemic fusion proteins observed in human patients.

    • Improved hematopoiesis in anemic Sl/Sld mice by splenectomy and therapeutic transplantation of a hematopoietic microenvironment
      Anklesaria, Pervin; Fitzgerald, Thomas J.; Kase, Kenneth; Ohara, Akira; Greenberger, Joel S. (1989-08-15)
      The ability of a clonal hematopoiesis-supportive bone-marrow stromal cell line GBlneor to engraft and alter the microenvironment-induced anemia of Sl/Sld mice was studied. Prior to stromal cell transplantation, Sl/Sld mice received 1 Gy total body irradiation (TBI) and 13 Gy to the right hind limb. Two months after intravenous (IV) injection of 5 x 10(5) GBlneor cells, 54.4% +/- 17.0% donor origin (G418r) colony-forming cells were recovered from the right hind limb of Sl/Sld mice. Long-term bone marrow cultures (LTBMCs) established from GBlneor-transplanted mice produced 189.5 CFU-GEMM-forming progenitors/flask over 10 weeks compared with 52.7 +/- 6.2 CFU-GEMM forming progenitors/flask from irradiated nontransplanted Sl/Sld mice. A partial correction of macrocytic anemia was detected 2 months after GBlneor transplantation in splenectomized, irradiated Sl/Sld mice (HgB 7.2 +/- 0.4 g/dL; MCV 68.3 +/- 7.0 fL) compared to splenectomized, irradiated, nontransplanted Sl/Sld mice (HgB 5.5 +/- 1.1 g/dL; MCV 76 +/- 8.5 fL) or control Sl/Sld mice (HgB 5.4 +/- 0.5 g/dL; MCV 82.4 +/- 1.3 fL). Mean RBC volume distribution analysis showed a 2.5-fold increase in percentage of peripheral blood RBCs with MCV less than or equal to 45 fL and confirmed reduction of the MCV in splenectomized-GBlneor-transplanted mice compared to control Sl/Sld mice. A hematopoiesis-suppressive clonal stromal cell line derived from LTBMCs of Sl/Sld mice (Sldneor) engrafted as effectively (43.5% +/- 1.2% G418r CFU-F/limb) as did GBlneor cells (38.3% +/- 0.16% G418r CFU-F/limb) to the irradiated right hind limbs of C57Bl/6 mice. LTBMCs established after 2 or 6 months from Sldneor-transplanted mice showed decreased hematopoiesis (182 +/- 12 [2 months] and 3494.3 +/- 408.1 [6 months] CFU-GEMM forming progenitors/flask over 10 weeks) compared to those established from GBlneor-transplanted mice (5980 +/- 530 [2 months] and 7728 +/- 607, [6 months] CFU-GEMM progenitors forming/flask). Thus, transplantation of clonal bone-marrow stromal cell lines in vivo can stably transfer their physiologic properties to normal or mutant mice.

    • Initiation of zebrafish haematopoiesis by the TATA-box-binding protein-related factor Trf3
      Hart, Daniel O.; Raha, Tamal; Lawson, Nathan D.; Green, Michael R. (2007-11-30)
      TATA-box-binding protein (TBP)-related factor 3, TRF3 (also called TBP2), is a vertebrate-specific member of the TBP family that has a conserved carboxy-terminal region and DNA-binding domain virtually identical to that of TBP (ref. 1). TRF3 is highly expressed during embryonic development, and studies in zebrafish and Xenopus have shown that it is required for normal embryogenesis. Here we show that zebrafish embryos depleted of Trf3 exhibit multiple developmental defects and, in particular, fail to undergo haematopoiesis. Expression profiling for Trf3-dependent genes identified mespa, which encodes a transcription factor whose murine orthologue is required for mesoderm specification, and chromatin immunoprecipitation verified that Trf3 binds to the mespa promoter. Depletion of Mespa resulted in developmental and haematopoietic defects markedly similar to those induced by Trf3 depletion. Injection of mespa messenger RNA (mRNA) restored normal development to a Trf3-depleted embryo, indicating mespa is the single Trf3 target gene required for zebrafish embryogenesis. Zebrafish embryos depleted of Trf3 or Mespa also failed to express cdx4, a caudal-related gene required for haematopoiesis. Mespa binds to the cdx4 promoter, and epistasis analysis revealed an ordered trf3-mespa-cdx4 pathway. Thus, in zebrafish, commitment of mesoderm to the haematopoietic lineage occurs through a transcription factor pathway initiated by a TBP-related factor.