title: Ordered chromatin changes and human X chromosome reactivation by cell fusion-mediated pluripotent reprogramming.
abstract: Erasure of epigenetic memory is required to convert somatic cells towards pluripotency. Reactivation of the inactive X chromosome (Xi) has been used to model epigenetic reprogramming in mouse, but human studies are hampered by Xi epigenetic instability and difficulties in tracking partially reprogrammed iPSCs. Here we use cell fusion to examine the earliest events in the reprogramming-induced Xi reactivation of human female fibroblasts. We show that a rapid and widespread loss of Xi-associated H3K27me3 and XIST occurs in fused cells and precedes the bi-allelic expression of selected Xi-genes by many heterokaryons (30-50%). After cell division, RNA-FISH and RNA-seq analyses confirm that Xi reactivation remains partial and that induction of human pluripotency-specific XACT transcripts is rare (1%). These data effectively separate pre- and post-mitotic events in reprogramming-induced Xi reactivation and reveal a complex hierarchy of epigenetic changes that are required to reactivate the genes on the human Xi chromosome.
authors: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors: Irene
authors: I
authors: Cantone
authors: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors: Hakan
authors: H
authors: Bagci
authors: Microscopy Laboratory, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors: Dirk
authors: D
authors: Dormann
authors: Bioinformatics and Computing facility, MRC Clinical Sciences Centre, Imperial College, London W12 0NN, UK.
authors: Gopuraja
authors: G
authors: Dharmalingam
authors: Developmental Epigenetics Group, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Tatyana
authors: 0000-0001-7740-4386
authors: T
authors: Nesterova
authors: Developmental Epigenetics Group, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors: Neil
authors: N
authors: Brockdorff
authors: Epigenetics and Cell Fate, CNRS UMR7216, Université Paris Diderot, Sorbonne Paris Cité, 75013 Paris, France.
authors: Claire
authors: C
authors: Rougeulle
authors: Epigenetics and Cell Fate, CNRS UMR7216, Université Paris Diderot, Sorbonne Paris Cité, 75013 Paris, France.
authors: Celine
authors: C
authors: Vallot
authors: Mammalian Developmental Epigenetics Group, Institut Curie, 26 rue d'Ulm, 75248 Paris, France.
authors: Edith
authors: E
authors: Heard
authors: Mammalian Developmental Epigenetics Group, Institut Curie, 26 rue d'Ulm, 75248 Paris, France.
authors: Ronan
authors: R
authors: Chaligne
authors: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors: Matthias
authors: M
authors: Merkenschlager
authors: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors: Amanda G
authors: AG
authors: Fisher
mesh_terms: D000818:Animals; D002459:Cell Fusion / Q000379:methods; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D065150:Cellular Reprogramming / Q000235:genetics*; D002843:Chromatin / Q000235:genetics*; D041321:Chromosomes, Human, X / Q000235:genetics*; D044127:Epigenesis, Genetic; D005260:Female; D005347:Fibroblasts; D006657:Histones / Q000235:genetics*; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism; D008297:Male; D051379:Mice; D008938:Mitosis; D000066450:Mouse Embryonic Stem Cells / Q000378:metabolism; D062085:RNA, Long Noncoding / Q000235:genetics*; D049951:X Chromosome Inactivation / Q000235:genetics*
chemical_list: D002843:Chromatin; D006657:Histones; D062085:RNA, Long Noncoding; C077885:XIST non-coding RNA