Cloned, fertilized stem cells look the same

Researchers at the Whitehead Institute in Cambridge, Massachusetts, have found that cultured stem cells from cloned mouse embryos have transcription profiles that are indistinguishable from those from normally fertilized embryos. The results, published in the January 24 issue of Proceedings of the National Academy of Sciences, support the hope that damaged cells could one day be safely replaced with cells carrying a patient?s own DNA."We knew from the phenotypic evidence that [the stem cells] were normal, but we had never done a detailed molecular analysis,? said Tobias Brambrink, first author on the paper. "From a molecular or a transcriptional point of view, stem cell lines, whether cloned or fertilization-derived, are indistinguishable," Brambrink said.Many embryos created by cloning carry fatal defects, often because the donor DNA has been modified to express only genes that were needed in the mature cell it was extracted from. For example, genes such as...