title: FMR1 epigenetic silencing commonly occurs in undifferentiated fragile X-affected embryonic stem cells.
abstract: Fragile X syndrome (FXS) is the most common heritable form of cognitive impairment. It results from epigenetic silencing of the X-linked FMR1 gene by a CGG expansion in its 5'-untranslated region. Taking advantage of a large set of FXS-affected human embryonic stem cell (HESC) lines and isogenic subclones derived from them, we show that FMR1 hypermethylation commonly occurs in the undifferentiated state (six of nine lines, ranging from 24% to 65%). In addition, we demonstrate that hypermethylation is tightly linked with FMR1 transcriptional inactivation in undifferentiated cells, coincides with loss of H3K4me2 and gain of H3K9me3, and is unrelated to CTCF binding. Taken together, these results demonstrate that FMR1 epigenetic gene silencing takes place in FXS HESCs and clearly highlights the importance of examining multiple cell lines when investigating FXS and most likely other epigenetically regulated diseases.
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Avitzour
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Hagar
authors.initials: H
authors.lastname: Mor-Shaked
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Shira
authors.initials: S
authors.lastname: Yanovsky-Dagan
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Shira
authors.initials: S
authors.lastname: Aharoni
authors.affiliation: Zohar PGD Lab, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Gheona
authors.initials: G
authors.lastname: Altarescu
authors.affiliation: Zohar PGD Lab, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Paul
authors.initials: P
authors.lastname: Renbaum
authors.affiliation: IVF Unit, Department of Obstetrics and Gynecology, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Talia
authors.initials: T
authors.lastname: Eldar-Geva
authors.affiliation: IVF Unit, Department of Obstetrics and Gynecology, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Oshrat
authors.initials: O
authors.lastname: Schonberger
authors.affiliation: Zohar PGD Lab, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Ephrat
authors.initials: E
authors.lastname: Levy-Lahad
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel.
authors.forename: Silvina
authors.initials: S
authors.lastname: Epsztejn-Litman
authors.affiliation: Stem Cell Research Laboratory, Medical Genetics Institute, Shaare Zedek Medical Center affiliated with the Hebrew University School of Medicine, Jerusalem 91031, Israel. Electronic address: rachela@szmc.org.il.
authors.forename: Rachel
authors.initials: R
authors.lastname: Eiges
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D019175:DNA Methylation; D053595:Embryonic Stem Cells / Q000378:metabolism*; D044127:Epigenesis, Genetic; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics* / Q000378:metabolism; D005600:Fragile X Syndrome / Q000235:genetics* / Q000473:pathology; D015870:Gene Expression; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D050814:Octamer Transcription Factor-3 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055748:SOXB1 Transcription Factors / Q000235:genetics; D017422:Sequence Analysis, DNA; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D049951:X Chromosome Inactivation
chemical_list: D020121:5' Untranslated Regions; D051860:Fragile X Messenger Ribonucleoprotein 1; D006657:Histones; D008239:Lysine; D050814:Octamer Transcription Factor-3; D055748:SOXB1 Transcription Factors; C497683:FMR1 protein, human; C494173:POU5F1 protein, human; C527782:SOX2 protein, human