Evolution of embryonic pluripotency

摘要

Embryonic stem cells can give rise to an array o: adult cell types, thanks in part to a network of gene switches that shut down the cells' program for differentiation and keep the cells in a pluri-potent state. Researchers have identified a hanc ful of these switches, called transcription factors in vertebrates, but the evolutionary conservatioi of the gene network controlling pluripotency is poorly understood. Beatriz Fernandez-Tres-guerres et al. (pp. 19955-19960) used genomic analysis and functional assays to compare the presence and activity of key pluripotency genes between undifferentiated chicken embryos and mouse embryonic stem cells. In contrast to mouse pluripotency genes, which are active in mouse embryonic stem cells, the authors report that the chick counterparts of key genes encoding some of the switches are not expressed in undifferentiated chicken embryos. Further, the authors could not find counterparts for several mouse genetic markers of pluripotency in transcriptional databases of chicken embryos. Further still, the authors found that the binding of specific gene switches to DNA and the genomic sequences to which the switches bound were not conserved between chick and mouse. The findings suggest that mammals might have evolved not only new pluripotency genes, perhaps by co-opting and duplicating existing ones, but also new regulatory interplay between those genes, according to the authors.