Developmental Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA.
Cell Rep. 2013 Mar 28;3(3):651-60. doi: 10.1016/j.celrep.2013.02.005. Epub 2013 Mar 7.
Induced pluripotent stem cells (iPSCs) hold great promise for personalized regenerative medicine. However, recent studies show that iPSC lines carry genetic abnormalities, suggesting that reprogramming may be mutagenic. Here, we show that the ectopic expression of reprogramming factors increases the level of phosphorylated histone H2AX, one of the earliest cellular responses to DNA double-strand breaks (DSBs). Additional mechanistic studies uncover a direct role of the homologous recombination (HR) pathway, a pathway essential for error-free repair of DNA DSBs, in reprogramming. This role is independent of the use of integrative or nonintegrative methods in introducing reprogramming factors, despite the latter being considered a safer approach that circumvents genetic modifications. Finally, deletion of the tumor suppressor p53 rescues the reprogramming phenotype in HR-deficient cells primarily through the restoration of reprogramming-dependent defects in cell proliferation and apoptosis. These mechanistic insights have important implications for the design of safer approaches to creating iPSCs.
诱导多能干细胞（iPSCs）在个性化再生医学方面具有巨大的潜力。然而，最近的研究表明，iPSC 系携带遗传异常，这表明重编程可能具有诱变作用。在这里，我们表明，重编程因子的异位表达会增加磷酸化组蛋白 H2AX 的水平，磷酸化组蛋白 H2AX 是细胞对 DNA 双链断裂（DSBs）的最早反应之一。进一步的机制研究揭示了同源重组（HR）途径在重编程中的直接作用，HR 途径是 DNA DSBs 无差错修复所必需的途径。尽管后者被认为是一种规避遗传修饰的更安全方法，但这种作用独立于引入重编程因子的整合或非整合方法。最后，HR 缺陷细胞中肿瘤抑制因子 p53 的缺失主要通过恢复细胞增殖和凋亡方面与重编程相关的缺陷来挽救重编程表型。这些机制上的见解对设计更安全的 iPSC 方法具有重要意义。
