Pasque Vincent, Tchieu Jason, Karnik Rahul, Uyeda Molly, Sadhu Dimashkie Anupama, Case Dana, Papp Bernadett, Bonora Giancarlo, Patel Sanjeet, Ho Ritchie, Schmidt Ryan, McKee Robin, Sado Takashi, Tada Takashi, Meissner Alexander, Plath Kathrin
Department of Biological Chemistry, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA 90095, USA.
Developmental Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Cell. 2014 Dec 18;159(7):1681-97. doi: 10.1016/j.cell.2014.11.040.
Reprogramming to iPSCs resets the epigenome of somatic cells, including the reversal of X chromosome inactivation. We sought to gain insight into the steps underlying the reprogramming process by examining the means by which reprogramming leads to X chromosome reactivation (XCR). Analyzing single cells in situ, we found that hallmarks of the inactive X (Xi) change sequentially, providing a direct readout of reprogramming progression. Several epigenetic changes on the Xi occur in the inverse order of developmental X inactivation, whereas others are uncoupled from this sequence. Among the latter, DNA methylation has an extraordinary long persistence on the Xi during reprogramming, and, like Xist expression, is erased only after pluripotency genes are activated. Mechanistically, XCR requires both DNA demethylation and Xist silencing, ensuring that only cells undergoing faithful reprogramming initiate XCR. Our study defines the epigenetic state of multiple sequential reprogramming intermediates and establishes a paradigm for studying cell fate transitions during reprogramming.
重编程为诱导多能干细胞会重置体细胞的表观基因组，包括X染色体失活的逆转。我们试图通过研究重编程导致X染色体重新激活（XCR）的方式，深入了解重编程过程的潜在步骤。通过对原位单细胞进行分析，我们发现失活X染色体（Xi）的特征会依次发生变化，从而直接反映重编程的进程。Xi上的几种表观遗传变化以与发育性X染色体失活相反的顺序发生，而其他变化则与该顺序无关。在后者中，DNA甲基化在重编程过程中在Xi上具有异常长的持续性，并且与Xist表达一样，仅在多能性基因激活后才被消除。从机制上讲，XCR需要DNA去甲基化和Xist沉默，以确保只有经历忠实重编程的细胞才会启动XCR。我们的研究定义了多个连续重编程中间体的表观遗传状态，并建立了一个研究重编程过程中细胞命运转变的范例。
