Report: Crazy Xs

March 28, 2008

Human embryonic stem cells (hESCs) are genetically unstable over time in culture, which raises concerns about their clinical safety. Epigenetic changes, heritable controls over gene expression that do not alter DNA sequence, in hESCs may contribute significantly to this instability. Two studies published recently in the Proceedings of the National Academy of Sciences used complementary methods to examine X-chromosome inactivation in hESCs, reporting that this particular epigenetic change shows an incredible amount of variability between hESC lines regardless of the source of derivation. (Nature)