title: Induced pluripotent stem cells as a model for telomeric abnormalities in ICF type I syndrome.
abstract: Human telomeric regions are packaged as constitutive heterochromatin, characterized by extensive subtelomeric DNA methylation and specific histone modifications. ICF (immunodeficiency, centromeric instability, facial anomalies) type I patients carry mutations in DNA methyltransferase 3B (DNMT3B) that methylates de novo repetitive sequences during early embryonic development. ICF type I patient fibroblasts display hypomethylated subtelomeres, abnormally short telomeres and premature senescence. In order to study the molecular mechanism by which the failure to de novo methylate subtelomeres results in accelerated telomere shortening, we generated induced pluripotent stem cells (iPSCs) from 3 ICF type I patients. Telomeres were elongated in ICF-iPSCs during reprogramming, and the senescence phenotype was abolished despite sustained subtelomeric hypomethylation and high TERRA levels. Fibroblast-like cells (FLs) isolated from differentiated ICF-iPSCs maintained abnormally high TERRA levels, and telomeres in these cells shortened at an accelerated rate, leading to early senescence, thus recapitulating the telomeric phenotype of the parental fibroblasts. These findings demonstrate that the abnormal telomere phenotype associated with subtelomeric hypomethylation is overridden in cells expressing telomerase, therefore excluding telomerase inhibition by TERRA as a central mechanism responsible for telomere shortening in ICF syndrome. The data in the current study lend support to the use of ICF-iPSCs for modeling of phenotypic and molecular defects in ICF syndrome and for unraveling the mechanism whereby subtelomeric hypomethylation is linked to accelerated telomeric loss in this syndrome.
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Shira
authors.initials: S
authors.lastname: Sagie
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Erika
authors.initials: E
authors.lastname: Ellran
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Hagar
authors.initials: H
authors.lastname: Katzir
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Rony
authors.initials: R
authors.lastname: Shaked
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Shiran
authors.initials: S
authors.lastname: Yehezkel
authors.affiliation: The Sohnis and Forman Families Stem Cell Center, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Ilana
authors.initials: I
authors.lastname: Laevsky
authors.affiliation: Computer Science Department, Technion, Haifa 32000, Israel.
authors.forename: Alaa
authors.initials: A
authors.lastname: Ghanayim
authors.affiliation: Computer Science Department, Technion, Haifa 32000, Israel.
authors.forename: Dan
authors.initials: D
authors.lastname: Geiger
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel.
authors.forename: Maty
authors.initials: M
authors.lastname: Tzukerman
authors.affiliation: Laboratory of Molecular Medicine, Rambam Health Care Campus and Rappaport Faculty of Medicine and Research Institute, Technion, Haifa 31096, Israel, seligs@tx.technion.ac.il.
authors.forename: Sara
authors.initials: S
authors.lastname: Selig
mesh_terms: D002478:Cells, Cultured; D065150:Cellular Reprogramming; D016922:Cellular Senescence; D002869:Chromosome Aberrations; D002877:Chromosomes, Human; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism; D005145:Face / Q000002:abnormalities* / Q000503:physiopathology; D005260:Female; D005347:Fibroblasts / Q000502:physiology; D006801:Humans; D007153:Immunologic Deficiency Syndromes / Q000235:genetics* / Q000503:physiopathology; D057026:Induced Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D000081207:Primary Immunodeficiency Diseases; D016615:Telomere / Q000378:metabolism*; D059506:Telomere Shortening; D000097584:DNA Methyltransferase 3B
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases; D004268:DNA-Binding Proteins; D000097584:DNA Methyltransferase 3B