Female human induced pluripotent stem cells (hiPSCs)

Female human induced pluripotent stem cell (hiPSC) lines exhibit considerable variability in X-inactivation status. Some lines maintain one transcriptionally active X chromosome (Xa) and one inactive X (Xi) from donor cells. However, hiPSC lines that have two Xas are infrequently produced. We show here Xinactivation status in female hiPSC lines depends on derivation conditions. hiPSC lines generated using the Kyoto method, which employs leukemia inhibitory factor (LIF)-expressing SNL feeders, frequently had two Xas. Lines derived on other feeders maintained an Xi. In addition, there appears to be a window in which SNL feeders promote Xi-reactivation. Upon differentiation, Xa/Xa hiPSCs silenced one X. The efficient production of Xa/Xa hiPSC lines provides unprecedented opportunities to understand human X-reactivation and inactivation. Gene expression patterns were compared between several human embryonic stem cell (hESC) and hiPSC lines. Gene expression ratios between genes on X and those on autosomes were calculated from each cell lines.