Primed and naive human embryonic stem cells (hESCs) do not fully recapitulate the X chromosome status observed in human preimplantation epiblast and fail to initiate random X chromosome inactivation (XCI) upon differentiation. Therefore, an ideal system for studying XCI during early human development is yet to be established. We show that incomplete blocking of autocrine fibroblast growth factor 2 (FGF2) signaling in naive hESCs drives significant heterogeneity in X chromosome and pluripotency status. We derived homozygous XaXa naive hESCs with dual allelic XIST expression and high levels of TFCP2L1, whose transcriptome and X chromosome states are similar to human preimplantation epiblast. Random XCI was initiated upon naive-to-primed conversion of these cells, and both pre- and post-XCI primed hESCs were obtained. We observed random XCI in all cells upon further differentiation of pre-XCI primed hESCs. Together, these findings enable derivation of homogeneous naive hESCs and establish a powerful platform to study human XCI.

初免和天真的人类胚胎干细胞（hESCs）不能完全概括在人类植入前的成骨细胞中观察到的X染色体状态，并且在分化后无法引发随机的X染色体失活（XCI）。因此，尚未建立在人类早期发展中研究XCI的理想系统。我们显示不完全阻止天真hESCs中的自分泌成纤维细胞生长因子2（FGF2）信号驱动X染色体和多能性状态显着异质性。我们使用双重等位基因XIST衍生了纯合XaXa天真hESCTFCP2L1的表达和高水平，其转录组和X染色体状态与人类植入前的成骨细胞相似。这些细胞从幼稚到初次转化后，会随机启动XCI，并且会获得XCI之前和之后的hESC。我们进一步预XCI引发hESCs分化后，在所有细胞中观察到随机XCI。在一起，这些发现使同质幼稚hESC的派生，并建立了一个强大的平台来研究人类XCI。