Recent studies have documented genome-wide binding patterns of transcriptional regulators and their associated epigenetic marks in hematopoietic cell lineages. In order to determine how epigenetic marks are established and maintained during developmental progression, we have generated long-term cultures of hematopoietic progenitors by enforcing the expression of the E-protein antagonist Id2. He...

Acute chicken leukemia retroviruses, because of their capacity to readily transform hematopoietic cells in vitro, are ideal models to study the mechanisms governing the cell-type specificity of oncoproteins. Here we analyzed the transformation specificity of 2 acute chicken leukemia retroviruses, the Myb-Ets- encoding E26 virus and the ErbA/ErbB-encoding avian erythroblastosis virus (AEV). Whil...

Acute chicken leukemia retroviruses, because of their capacity to readily transform hematopoietic cells in vitro, are ideal models to study the mechanisms governing the cell-type specificity of oncoproteins. Here we analyzed the transformation specificity of 2 acute chicken leukemia retroviruses, the Myb-Ets– encoding E26 virus and the ErbA/ErbBencoding avian erythroblastosis virus (AEV). While...

In this issue of Cell, a study by Adolfsson and coworkers (Adolfsson et al., 2005) provides insight into the early lineage commitment events of multipotent hematopoietic stem cells (HSCs). These studies demonstrate the importance of the Flt3 receptor tyrosine kinase as the earliest marker of hematopoietic cell fate commitment in that erythrocyte and megakaryocyte potentials are lost first as HS...

Development of the hematopoietic system proceeds in a multistep manner. Primitive erythrocytes are the first hematopoietic cells to be observed that were produced transiently in developing embryos. Multilineage lymphohematopoiesis occurs after the primitive erythropoiesis. However, the lineage relationship of cells that comprise embryonic hematopoietic system is not well characterized. To clari...

The role of cytokines in the control of hematopoietic cell differentiation remains controversial. Two general models for the cytokine control of hematopoietic differentiation have been proposed. In the stochastic model, cytokines provide proliferative and survival signals to the differentiating hematopoietic cell, but they do not provide specific lineage commitment signals. In the instructive m...

The identification of clonal human multipotent hematopoietic progenitors has permitted an analysis of the growth factor requirements for these cells. Human endothelial cell cultures were used to examine the effects of media conditioned by the endothelial cells on human multipotent (CFU-mix) and committed erythroid (BFU-E, CFU-E) and myeloid (CFU-GM) precursors. These studies demonstrate that en...

Development of mature blood cell progenies from hematopoietic stem cells involves the transition through lineage-restricted progenitors. The first branching point along this developmental process is thought to separate the erythro-myeloid and lymphoid lineage fate by yielding two intermediate progenitors, the common myeloid and the common lymphoid progenitors (CMPs and CLPs). Here, we use singl...

BACKGROUND Hematopoiesis originates from the dorsal aorta during embryogenesis. Although adult blood vessels harbor progenitor populations for endothelial and smooth muscle cells, it is not known if they contain hematopoietic progenitor or stem cells. Here, we hypothesized that the arterial wall is a source of hematopoietic progenitor and stem cells in postnatal life. METHODS AND RESULTS Sing...