"Stemness"

The recent isolation of human embryonic stem cells and the demonstration of their remarkable pluripotency have focused attention on the properties of stem cells. Two studies published in the September 12 Sciencexpress, use functional genomics to investigate common features of stem-cell populations of different origins. Both groups used Affymetrix oligonucleotide microarrays covering around 12,000 genes to investigate the stem-cell transcriptome. Ramalho-Santos et al. carried out transcription profiling of embryonic, neural and hematopoietic stem cells from mice, in the same experiment (Sciencexpress DOI:10.1126/science.1072530). Each stem-cell population had its own set of highly enriched genes, and 216 genes were enriched in all three stem-cell groups, revealing the core set required for "stemness" attributes. In the same issue, Ivanova et al. report their comparison of the gene expression profiles of either human or murine hematopoietic stem cells, compared with the non-hematopoietic embryonic and neural stem cells (Sciencexpress DOI:10.1126/science.1073823). The two types of hematopoietic stem cells shared a considerable number of genes, including those involved in signal transduction pathways, cell-cycle regulation and gene transcription. The challenge remains to link 'stemness' signatures to distinct biological features of stem cells.