Stem cells made from mature cells and rewound to an embryonic-like state retain a distinct "memory" of their past that might limit their potential for therapeutic use, scientists reported Wednesday in the journal Nature. [...] They looked at 1.2 billion places in each genome where such chemical markers [epigenomes] exist. The analysis was unusually rigorous — and therefore unusually revealing, Ecker said. Earlier studies examined representative regions in the genome, rather than the whole thing. [...] For the most part, the contents of Ecker's metaphorical rooms looked alike. But when they zoomed in, inconsistencies emerged. In a side-by-side comparison of...