1: Development. 2005 Mar;132(5):1117-26. Epub 2005 Feb 2. 

RBPjkappa-dependent Notch function regulates Gata2 and is essential for the
formation of intra-embryonic hematopoietic cells.

Robert-Moreno A, Espinosa L, de la Pompa JL, Bigas A.

Centre Oncologia Molecular, IDIBELL-Institut de Recerca Oncologica, Hospitalet,
Barcelona 08907, Spain.

Definitive hematopoiesis in the mouse embryo originates from the aortic floor in
the P-Sp/AGM region in close association with endothelial cells. An important
role for Notch1 in the control of hematopoietic ontogeny has been recently
established, although its mechanism of action is poorly understood. Here, we
show detailed analysis of Notch family gene expression in the aorta endothelium
between embryonic day (E) 9.5 and E10.5. Since Notch requires binding to
RBPjkappa transcription factor to activate transcription, we analyzed the aorta
of the para-aortic splanchnopleura/AGM in RBPjkappa mutant embryos. We found
specific patterns of expression of Notch receptors, ligands and Hes genes that
were lost in RBPjkappa mutants. Analysis of these mutants revealed the absence
of hematopoietic progenitors, accompanied by the lack of expression of the
hematopoietic transcription factors Aml1/Runx1, Gata2 and Scl/Tal1. We show that
in wild-type embryos, a few cells lining the aorta endothelium at E9.5
simultaneously expressed Notch1 and Gata2, and demonstrate by chromatin
immunoprecipitation that Notch1 specifically associated with the Gata2 promoter
in E9.5 wild-type embryos and 32D myeloid cells, an interaction lost in
RBPjkappamutants. Consistent with a role for Notch1 in regulating Gata2, we
observe increased expression of this gene in 32D cells expressing activated
Notch1. Taken together, these data strongly suggest that activation of Gata2
expression by Notch1/RBPjkappa is a crucial event for the onset of definitive
hematopoiesis in the embryo.

PMID: 15689374 [PubMed - indexed for MEDLINE]


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2: Biochem Biophys Res Commun. 2004 Jan 2;313(1):125-8. 

Negative regulation of hematopoiesis by the fused in myeloproliferative
disorders gene product.

Inoue H, Nobuhisa I, Okita K, Takizawa M, Pebusque MJ, Taga T.

Department of Cell Fate Modulation, Institute of Molecular Embryology and
Genetics, Kumamoto University, Kumamoto, Japan.

The t(8;13) translocation, found in a rare and aggressive type of stem cell
myeloproliferative disorder, leads to the generation of a fusion protein between
the N-terminal gene product of fused in myeloproliferative disorders
(FIM)/ZNF198 and the fibroblast growth factor receptor 1 (FGFR1) kinase domain.
The chimeric protein was reported to have constitutively activated tyrosine
kinase activity. However, little is known about a role of FIM in hematopoietic
cell regulation. Here we show that FIM protein is ubiquitously expressed in
mouse embryonic tissues but much less in hematopoietic cells. We also show that
forced expression of FIM inhibits the emergence of hematopoietic cells in the
cultured mouse aorta-gonad-mesonephros (AGM) region on embryonic day (E) 11.5,
where definitive hematopoiesis is first found during embryogenesis. These
results suggest that the expression level of FIM determines the development of
hematopoiesis during mouse ontogeny.

PMID: 14672707 [PubMed - indexed for MEDLINE]


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3: Br J Haematol. 2001 Apr;113(1):52-7. 

Decreased expression of transcription factor GATA-2 in haematopoietic stem cells
in patients with aplastic anaemia.

Fujimaki S, Harigae H, Sugawara T, Takasawa N, Sasaki T, Kaku M.

Department of Molecular Diagnostics, Tohoku University School of Medicine,
Sendai, Japan.

Aplastic anaemia is characterized by reduced haematopoiesis resulting in
pancytopenia. It has been speculated that there is an injury in haematopoietic
stem cells in the bone marrow; however, the precise nature of the injury has not
been elucidated. In this study, the levels of expression of mRNAs for three
transcription factors, GATA-2, SCL and AML1, which function in the early stages
of haematopoiesis, were examined by quantitative polymerase chain reaction in
patients with aplastic anaemia, idiopathic thrombocytopenic purpura (ITP) and
normal subjects. Among these factors, expression of GATA-2 mRNA in purified
CD34-positive cells was markedly decreased in aplastic anaemia compared with
that in ITP and in normal subjects. The expression levels of SCL and AML1 mRNA
in CD34-positive cells in aplastic anaemia were not different from those in
normal subjects. When the expression of GATA-2 protein in CD34-positive cells
was examined by immunocytochemical analysis, the percentage of GATA-2-positive
cells in aplastic anaemia was lower than that in normal subjects. These findings
strongly suggest that there is an aberrant expression of transcription factors
in stem cells in aplastic anaemia, which may be responsible for the development
of the disease.

PMID: 11328281 [PubMed - indexed for MEDLINE]


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