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Department of Medicine University of Massachusetts Cancer Center

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Animals; Bone Marrow Cells; *Cell Cycle; Cell Division; Cell Line; Fetus; Gene Expression Regulation, Developmental; *Helix-Loop-Helix Motifs; Hematopoietic Stem Cells; Humans; Inhibitor of Differentiation Protein 1; Kinetics; Liver; Mice; Mice, Inbred CBA; *Multigene Family; Polymerase Chain Reaction; *Repressor Proteins; Transcription Factors; Tumor Cells, Cultured


Cancer Biology | Cell and Developmental Biology


To better understand the molecular mechanism(s) by which growth and differentiation of the primitive hematopoietic stem cell is initiated, as well as the means by which the maturing cell can commit to development along a specific cell lineage, we elected to study the Id family of helix-loop-helix (HLH) transcriptional regulators. Some members of the HLH family are expressed in a stage-specific manner during hematopoietic development and can regulate the ability of immature hematopoietic cells to terminally differentiate. None of the four Id family genes were detected in the most primitive progenitors. Id-1 was widely expressed in proliferating bi- and unipotential progenitors, but its expression was downregulated in cells of increasing maturity; conversely, Id-2 and, to a limited extent, Id-3 gene expression increased as cells matured and lost proliferative capacity. Id-2 expression ran counter to that of Id-1 not only during maturation, but during periods of cell growth and arrest as well. This is quite distinct from the nonhematopoietic tissues, in which these two factors are coordinately expressed and suggests that Id-1 and Id-2 might be regulating very different events during hematopoiesis than they regulate in other cell types.


Blood. 1997 May 1;89(9):3155-65.

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