AC133+ G0 cells from cord blood show a high incidence of long-term culture-initiating cells and a capacity for more than 100 million-fold amplification of colony-forming cells in vitro.

AC133+ cells may provide an alternative to CD34+ cells as a target for cell expansion and gene therapy protocols. We examined the differences in proliferative potential between cord blood selected for AC133 or CD34 in serum-free, stroma cell-free culture for up to 30 weeks. Because most hemopoietic stem cells reside within the G0/G1 phase of the cell cycle, we combined enrichment according to AC133 or CD34 expression with G0 position in the cell cycle to identify populations enriched for putative stem cells.

Globin gene activation during haemopoiesis is driven by protein complexes nucleated by GATA-1 and GATA-2.

How does an emerging transcriptional programme regulate individual genes as stem cells undergo lineage commitment, differentiation and maturation? To answer this, we have analysed the dynamic protein/DNA interactions across 130 kb of chromatin containing the mouse alpha-globin cluster in cells representing all stages of differentiation from stem cells to mature erythroblasts. The alpha-gene cluster appears to be inert in pluripotent cells, but priming of expression begins in multipotent haemopoietic progenitors via GATA-2. In committed erythroid progenitors, GATA-2 is replaced by GATA-1 and binding is extended to additional sites including the alpha-globin promoters.

Molecular signatures of self-renewal, differentiation, and lineage choice in multipotential hemopoietic progenitor cells in vitro.

The molecular mechanisms governing self-renewal, differentiation, and lineage specification remain unknown. Transcriptional profiling is likely to provide insight into these processes but, as yet, has been confined to "static" molecular profiles of stem and progenitors cells. We now provide a comprehensive, statistically robust, and "dynamic" analysis of multipotent hemopoietic progenitor cells undergoing self-renewal in response to interleukin-3 (IL-3) and multilineage differentiation in response to lineage-affiliated cytokines.

The human granulocyte/macrophage colony-stimulating factor receptor alpha2 isoform influences haemopoietic lineage commitment and divergence.

A number of alternatively spliced isoforms of haemopoietic growth factor receptors (HGFRs) have been described, but their role in human haemopoiesis remains undetermined. We have investigated the relative expression of the alpha1 and alpha2 isoforms of human granulocyte/macrophage colony-stimulating factor receptor (hGM-CSFR) during haemopoietic cell differentiation, and have shown that both subunits are independently regulated during differentiation of CD34+ human haemopoietic progenitor cells. To further investigate these ex-vivo observations, we established a series of murine FDCP mix cell lines, which, as a consequence of the ectopic expression of alpha1 or alpha2 hGM-CSFR, demonstrated differential differentiation responses to hGM-CSF.

Transcription factor-mediated lineage switching reveals plasticity in primary committed progenitor cells.

The developmental plasticity of transplanted adult stem cells challenges the notion that tissue-restricted stem cells have stringently limited lineage potential and prompts a re-evaluation of the stability of lineage commitment. Transformed cell systems are inappropriate for such studies, since transformation potentially dysregulates the processes governing lineage commitment. We have therefore assessed the stability of normal lineage commitment in primary adult haematopoietic cells.