ABSTRACT
Lymphoid-primed multipotent progenitors with down-regulated megakaryocyte-erythroid (MkE) potential are restricted to cells with high levels of cell-surface FLT3 expression, whereas HSCs and MkE progenitors lack detectable cell-surface FLT3. These findings are compatible with FLT3 cell-surface expression not being detectable in the fully multipotent stem/progenitor cell compartment in mice. If so, this process could be distinct from human hematopoiesis, in which FLT3 already is expressed in multipotent stem/progenitor cells. The expression pattern of Flt3 (mRNA) and FLT3 (protein) in multipotent progenitors is of considerable relevance for mouse models in which prognostically important Flt3 mutations are expressed under control of the endogenous mouse Flt3 promoter. Herein, we demonstrate that mouse Flt3 expression initiates in fully multipotent progenitors because in addition to lymphoid and granulocyte-monocyte progenitors, FLT3(-) Mk- and E-restricted downstream progenitors are also highly labeled when Flt3-Cre fate mapping is applied.
Subject(s)
Gene Expression Profiling , Hematopoietic Stem Cells/metabolism , Multipotent Stem Cells/metabolism , fms-Like Tyrosine Kinase 3/genetics , Animals , Bone Marrow Cells/cytology , Bone Marrow Cells/metabolism , Bone Marrow Transplantation , Cell Lineage/genetics , Cell Membrane/metabolism , Erythroid Precursor Cells/cytology , Erythroid Precursor Cells/metabolism , Flow Cytometry , Granulocyte Precursor Cells/cytology , Granulocyte Precursor Cells/metabolism , Hematopoietic Stem Cells/cytology , Humans , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Megakaryocyte Progenitor Cells/cytology , Megakaryocyte Progenitor Cells/metabolism , Mice , Mice, Inbred C57BL , Mice, Transgenic , Monocytes/cytology , Monocytes/metabolism , Multipotent Stem Cells/cytology , Reverse Transcriptase Polymerase Chain Reaction , fms-Like Tyrosine Kinase 3/metabolismABSTRACT
GATA3 has been identified as a master regulator of T helper cells, as well as being important for early thymic progenitors and T-cell commitment. However, Gata3 expression initiates already at the hematopoietic stem cell (HSC) level, implicating a potential role also in the regulation of HSCs. Herein we used a conditional Gata3 knockout strategy in which Gata3 expression was completely deleted from the earliest stage of embryonic hematopoietic development after emergence of HSCs from hemogenic endothelium. Through a detailed analysis of HSCs at the phenotypic and functional level, we demonstrate that steady-state levels of HSCs are normal in Gata3(fl/fl)Vav-Cre(tg/+) mice. Moreover, through long-term primary and secondary transplantation experiments, we also unequivocally demonstrate that Gata3 has a redundant role in post-transplantation HSC self-renewal.
