Biomedical subjects

Marella F T R de Bruijn

Publications and source records attributed to Marella F T R de Bruijn.

8 recordsLinked to original sources

PubMed2007

The SCL transcriptional network and BMP signaling pathway interact to regulate RUNX1 activity.

Hematopoietic stem cell (HSC) development is regulated by several signaling pathways and a number of key transcription factors, which include Scl/Tal1, Runx1, and members of the Smad family. However, it remains unclear how these various determinants interact. Using a genome-wide computational screen based on the well characterized Scl +19 HSC enhancer, we have identified a related Smad6 enhancer that also targets expression to blood and endothelial cells in transgenic mice. Smad6, Bmp4, and Runx1 transcripts are concentrated along the ventral aspect of the E10.5 dorsal aorta in the aorta-gonad-mesonephros region from which HSCs originate. Moreover, Smad6, an inhibitor of Bmp4 signaling, binds and inhibits Runx1 activity, whereas Smad1, a positive mediator of Bmp4 signaling, transactivates the Runx1 promoter. Taken together, our results integrate three key determinants of HSC development; the Scl transcriptional network, Runx1 activity, and the Bmp4/Smad signaling pathway.

Animals↗

PubMed2004

Core-binding factors in hematopoiesis and immune function.

Core binding factors are heterodimeric transcription factors containing a DNA binding Runx1, Runx2, or Runx3 subunit, along with a non DNA binding CBF beta subunit. All four subunits are required at one or more stages of hematopoiesis. This review describes the role of Runx1 and CBF beta in the initiation of hematopoiesis in the embryo, and in the emergence of hematopoietic stem cells. We also discuss the later stages of hematopoiesis for which members of the core binding factor family are required, as well as the recently described roles for these proteins in autoimmunity.

Animals↗

PubMed2004

Runx1 is expressed in adult mouse hematopoietic stem cells and differentiating myeloid and lymphoid cells, but not in maturing erythroid cells.

The transcription factor Runx1 marks all functional hematopoietic stem cells (HSCs) in the embryo and is required for their generation. Mutations in Runx1 are found in approximately 25% of acute leukemias and in familial platelet disorder, suggesting a role for Runx1 in adult hematopoiesis as well. A comprehensive analysis of Runx1 expression in adult hematopoiesis is lacking. Here we show that Runx1 is expressed in functional HSCs in the adult mouse, as well as in cells with spleen colony-forming unit (CFU) and culture CFU capacities. Additionally, we document Runx1 expression in all hematopoietic lineages at the single cell level. Runx1 is expressed in the majority of myeloid cells and in a smaller proportion of lymphoid cells. Runx1 expression substantially decreases during erythroid differentiation. We also document effects of reduced Runx1 levels on adult hematopoiesis.

Animals↗

PubMed2003

Interleukin-3Ralpha+ myeloid dendritic cells and mast cells develop simultaneously from different bone marrow precursors in cultures with interleukin-3.

The distinct developmental routes of dendritic cells and mast cells from murine bone marrow cultures with interleukin-3 are unclear. We found that short-term bone marrow cultures with interleukin-3 after 8-10 d consist of about 10%-30% dendritic cells and 70%-90% mast cell precursors, and only after 4-6 wk do homogeneous populations of mast cells emerge. Phenotypical and functional analysis of interleukin-3/dendritic cells revealed a high similarity with myeloid dendritic cells generated with granulocyte-macrophage colony stimulating factor in the expression of myeloid dendritic cell markers (CD11c+ B220- CD8alpha- CD11b+), major histocompatibility complex II and costimulatory molecules, endocytosis, maturation potential, interleukin-12 production, and T cell priming. Interleukin-3/dendritic cells expressed higher levels of interleukin-3 receptor, however. To dissect the interleukin-3/dendritic cell and mast cell development, we sorted fresh bone marrow cells into six subsets by the antibodies ER-MP12 (CD31) and ER-MP20 (Ly-6C). Both interelukin-3/dendritic cells and granulocyte-macrophage colony stimulating factor/dendritic cells develop from the same bone marrow populations, including the ER-MP12neg, ER-MP20high bone marrow monocytes. In contrast, mast cells only developed from ER-MP12(int+high), ER-MP20neg bone marrow cell subsets, indicating that different precursors exist for interleukin-3/dendritic cells and mast cells. Established mast cell cultures could not be converted to dendritic cells or stimulated to express major histocompatibility complex II molecules in vitro or home to lymph node T cell areas in vivo. In summary, we show that dendritic cells generated from bone marrow precursors with interleukin-3 are clearly myeloid and develop via a different pathway compared to bone marrow mast cells.

Animals↗

PubMed2003

Developmental stages of myeloid dendritic cells in mouse bone marrow.

The lineage relationship of dendritic cells (DC) with other hematopoietic cell types has been studied extensively, resulting in the identification of different bone marrow (BM) progenitors that give rise to distinct DC types. However, the identity of the different maturation stages of DC precursors in the BM remains unclear. In this study we define the in vivo developmental steps of the myeloid DC lineage in mouse BM. To this end, BM cells were separated according to their expression of CD31 (ER-MP12), Ly-6C (ER-MP20) and ER-MP58 antigens, and stimulated to develop into myeloid DC, using granulocyte macrophage colony stimulating factor as a specific growth factor. DC developed from three BM subpopulations: ER-MP12(hi)/20(-) (early blast cells), ER-MP12(+)/20(+) (myeloid blasts) and ER-MP12(-)/20(hi) (monocytes). The kinetic and phenotypic features of DC developing in vitro indicate that the three populations represent successive maturation stages of myeloid DC precursors. Within the earliest ER-MP12(hi)/20(-) population, DC precursors exclusively occurred in the myeloid-restricted ER-MP58(hi) subset. By using switch cultures, we show that these BM precursor subpopulations, when stimulated to develop into macrophages using macrophage colony stimulating factor, retain the ability to develop into myeloid DC until advanced stages of maturation. Together, these findings support a common ER-MP12/20-defined differentiation pathway for both macrophages and myeloid DC throughout their BM development.

Animals↗

PubMed2002

Stromal cell lines from mouse aorta-gonads-mesonephros subregions are potent supporters of hematopoietic stem cell activity.

The aorta-gonads-mesonephros (AGM) region autonomously generates the first adult repopulating hematopoietic stem cells (HSCs) in the mouse embryo. HSC activity is initially localized to the dorsal aorta and mesenchyme (AM) and vitelline and umbilical arteries. Thereafter, HSC activity is found in the urogenital ridges (UGs), yolk sac, and liver. As increasing numbers of HSCs are generated, it is thought that these sites provide supportive microenvironments in which HSCs are harbored until the bone marrow microenvironment is established. However, little is known about the supportive cells within these midgestational sites, and particularly which microenvironment is most supportive for HSC growth and maintenance. Thus, to better understand the cells and molecules involved in hematopoietic support in the midgestation embryo, more than 100 stromal cell lines and clones were established from these sites. Numerous stromal clones were found to maintain hematopoietic progenitors and HSCs to a similar degree as, or better than, previously described murine stromal lines. Both the AM and UG subregions of the AGM produced many supportive clones, with the most highly HSC-supportive clone being derived from the UGs. Interestingly, the liver at this stage yielded only few supportive stromal clones. These results strongly suggest that during midgestation, not only the AM but also the UG subregion provides a potent microenvironment for growth and maintenance of the first HSCs.

Animals↗

PubMed2002

Runx1 expression marks long-term repopulating hematopoietic stem cells in the midgestation mouse embryo.

Hematopoietic stem cells (HSCs) are first found in the aorta-gonad-mesonephros region and vitelline and umbilical arteries of the midgestation mouse embryo. Runx1 (AML1), the DNA binding subunit of a core binding factor, is required for the emergence and/or subsequent function of HSCs. We show that all HSCs in the embryo express Runx1. Furthermore, HSCs in Runx1(+/-) embryos are heterogeneous and include CD45(+) cells, endothelial cells, and mesenchymal cells. Comparison with wild-type embryos showed that the distribution of HSCs among these various cell populations is sensitive to Runx1 dosage. These data provide the first morphological description of embryonic HSCs and contribute new insight into their cellular origin.

Animals↗

PubMed2002

Hematopoietic stem cells localize to the endothelial cell layer in the midgestation mouse aorta.

The emergence of the first adult hematopoietic stem cells (HSCs) during mammalian ontogeny has been under intense investigation. It is as yet unresolved whether these first HSCs are derived from intraembryonic hemangioblasts, hemogenic endothelial cells, or other progenitors. Thus, to examine the spatial generation of functional HSCs within the mouse embryo, we used the well-known HSC marker, Sca-1, and a transgenic approach with an Ly-6A (Sca-1) GFP marker gene. Our results show that this transgene marker is expressed in all functional HSCs in the midgestation aorta. Immunohistology of aorta-gonads-mesonephros (AGM) regions show that GFP(+) cells are specifically localized to the endothelial layer lining the wall of the dorsal aorta but not to the mesenchyme, strongly suggesting that HSC activity arises within a few cells within the endothelium of the major vasculature.

Animals↗