title: X-inactivation reveals epigenetic anomalies in most hESC but identifies sublines that initiate as expected.
abstract: The clinical and research value of human embryonic stem cells (hESC) depends upon maintaining their epigenetically naïve, fully undifferentiated state. Inactivation of one X chromosome in each cell of mammalian female embryos is a paradigm for one of the earliest steps in cell specialization through formation of facultative heterochromatin. Mouse ES cells are derived from the inner cell mass (ICM) of blastocyst stage embryos prior to X-inactivation, and cultured murine ES cells initiate this process only upon differentiation. Less is known about human X-inactivation during early development. To identify a human ES cell model for X-inactivation and study differences in the epigenetic state of hESC lines, we investigated X-inactivation in all growth competent, karyotypically normal, NIH approved, female hESC lines and several sublines. In the vast majority of undifferentiated cultures of nine lines examined, essentially all cells exhibit hallmarks of X-inactivation. However, subcultures of any hESC line can vary in X-inactivation status, comprising distinct sublines. Importantly, we identified rare sublines that have not yet inactivated Xi and retain competence to undergo X-inactivation upon differentiation. Other sublines exhibit defects in counting or maintenance of XIST expression on Xi. The few hESC sublines identified that have not yet inactivated Xi may reflect the earlier epigenetic state of the human ICM and represent the most promising source of NIH hESC for study of human X-inactivation. The many epigenetic anomalies seen indicate that maintenance of fully unspecialized cells, which have not formed Xi facultative heterochromatin, is a delicate epigenetic balance difficult to maintain in culture.
authors.affiliation: Department of Cell Biology, U Mass Med School, Worcester, Massachusetts 01655, USA. lisa.hall@umassmed.edu
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Hall
authors.forename: Meg
authors.initials: M
authors.lastname: Byron
authors.forename: John
authors.initials: J
authors.lastname: Butler
authors.forename: Klaus A
authors.initials: KA
authors.lastname: Becker
authors.forename: Angel
authors.initials: A
authors.lastname: Nelson
authors.forename: Michal
authors.initials: M
authors.lastname: Amit
authors.forename: Joseph
authors.initials: J
authors.lastname: Itskovitz-Eldor
authors.forename: Janet
authors.initials: J
authors.lastname: Stein
authors.forename: Gary
authors.initials: G
authors.lastname: Stein
authors.forename: Carol
authors.initials: C
authors.lastname: Ware
authors.forename: Jeanne B
authors.initials: JB
authors.lastname: Lawrence
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D041321:Chromosomes, Human, X; D004303:Dosage Compensation, Genetic; D053595:Embryonic Stem Cells / Q000166:cytology / Q000502:physiology*; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D051379:Mice; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism; D049951:X Chromosome Inactivation
chemical_list: D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C077885:XIST non-coding RNA