Analysis of gene expression in subpopulations of murine hematopoietic stem and progenitor cells.

The aim of the present work was to study how functional differences between subsets of the murine hematopoietic stem/progenitor cell compartment are manifested on the level of different patterns of gene expression in these subsets. Amplified 3' terminal total cDNA fragment populations from four stem and progenitor cell fractions sorted using differential staining with Rhodamine 123 were prepared, and gene expression patterns were analyzed by Southern hybridization with a panel of gene markers. For the vast majority of lineage-specific markers, no expression was detected in the long-term repopulating stem cell fraction. Expression of a number of key genes positively regulating entry and progression through the cell cycle was down-regulated in long-term repopulating cells, in accordance with the quiescent state of the latter. In contrast, certain but not all cell division kinase inhibitors were significantly up-regulated in long- and short-term repopulating stem cell fractions. Expression of several genes important for entry into the apoptotic pathway was moderately reduced in long-term repopulating cells. Messenger RNA levels of the transcription factors GATA-1, GATA-2, c-Myb and SCL were down-regulated in long-term repopulating cells, as compared to more mature stem/progenitor cells. Finally, expression of the MDR1a gene encoding the Pgp efflux pump was highest in long-term repopulating cells, and progressively decreased with maturation. The patterns of gene expression in the stem/progenitor cell fractions are in good correlation with the known properties of adult hematopoietic stem/progenitor cells and may provide insight into molecular mechanisms underlying stem cell physiology.