Derivation Conditions Impact X-Inactivation Status in Female Human Induced Pluripotent Stem Cells

Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, San Francisco, CA 94158, USA.
Cell stem cell (Impact Factor: 22.27). 07/2012; 11(1):91-9. DOI: 10.1016/j.stem.2012.05.019
Source: PubMed


Female human induced pluripotent stem cell (hiPSC) lines exhibit variability in X-inactivation status. The majority of hiPSC lines maintain one transcriptionally active X (Xa) and one inactive X (Xi) chromosome from donor cells. However, at low frequency, hiPSC lines with two Xas are produced, suggesting that epigenetic alterations of the Xi occur sporadically during reprogramming. We show here that X-inactivation status in female hiPSC lines depends on derivation conditions. hiPSC lines generated by the Kyoto method (retroviral or episomal reprogramming), which uses leukemia inhibitory factor (LIF)-expressing SNL feeders, frequently had two Xas. Early passage Xa/Xi hiPSC lines generated on non-SNL feeders were converted into Xa/Xa hiPSC lines after several passages on SNL feeders, and supplementation with recombinant LIF caused reactivation of some of X-linked genes. Thus, feeders are a significant factor affecting X-inactivation status. The efficient production of Xa/Xa hiPSC lines provides unprecedented opportunities to understand human X-reactivation and -inactivation.

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    • "Taken together, these reports lead to the conclusion that hPSCs and EpiSCs share a similar pluripotency state characterised by their dependency on Activin/Nodal signalling. Nevertheless, hESCs and EpiSCs are not strictly identical: contrary to EpiSCs, hESCs express pre-implantation markers such as REX1 (Chan et al., 2009) and not post-implantation markers such as FGF5 (Vallier et al., 2004), and also can exhibit X activation, indicative of pre-implantation stages (Lengner et al., 2010; Tomoda et al., 2012). These observations could underline species divergence. "
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    • "Somatic stem cells reside in niches, and environmental changes, such as temperature, extracellular matrix proteins, stromal cell contacts, and oxygen tension, have a great influence on stem cell function and differentiation. For example, Tomoda et al. have recently reported that culturing conditions can influence the X chromosome inactivation status in hiPSC1213. X-chromosome reactivation (XaXa), a characteristic of naïve pluripotent state cells, rarely occurs during the reprogramming of human female somatic cells to induced pluripotent stem cells. Furthermore, mammalian embryonic epiblasts reside in a physiologically hypoxic environment, and culturing ESCs in a hypoxic environment is known to prevent differentiation of human ESCs and enhance generation of human and mouse iPS colonies141516. "
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    • "Two clones of dfD551K1-iPSC showed expression of the TT SNP GRPR of the parental fibroblasts (Tchieu et al., 2010). We found that six dfD551K1-iPSC clones expressed both AA and TT alleles of GRPR that may have acquired two active X chromosomes via X chromosome reactivation (XCR) during reprogramming (Tomoda et al., 2012). However , unexpectedly, two clones of dfD551K1-iPSC expressed GRPR with the AA allele. "
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