title: Reactivation of developmentally silenced globin genes by forced chromatin looping.
abstract: Distal enhancers commonly contact target promoters via chromatin looping. In erythroid cells, the locus control region (LCR) contacts β-type globin genes in a developmental stage-specific manner to stimulate transcription. Previously, we induced LCR-promoter looping by tethering the self-association domain (SA) of Ldb1 to the β-globin promoter via artificial zinc fingers. Here, we show that targeting the SA to a developmentally silenced embryonic globin gene in adult murine erythroblasts triggers its transcriptional reactivation. This activity depends on the LCR, consistent with an LCR-promoter looping mechanism. Strikingly, targeting the SA to the fetal γ-globin promoter in primary adult human erythroblasts increases γ-globin promoter-LCR contacts, stimulating transcription to approximately 85% of total β-globin synthesis, with a reciprocal reduction in adult β-globin expression. Our findings demonstrate that forced chromatin looping can override a stringent developmental gene expression program and suggest a novel approach to control the balance of globin gene transcription for therapeutic applications.
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; Transcription Imaging Consortium, Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
authors.forename: Wulan
authors.initials: W
authors.lastname: Deng
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Rupon
authors.affiliation: Laboratory of Cellular and Developmental Biology, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Krivega
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, Weill Cornell Medical College, New York, NY 10021, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Breda
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, Weill Cornell Medical College, New York, NY 10021, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Motta
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA.
authors.forename: Kristen S
authors.initials: KS
authors.lastname: Jahn
authors.affiliation: Sangamo BioSciences, Richmond, CA 94804, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Reik
authors.affiliation: Sangamo BioSciences, Richmond, CA 94804, USA.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Gregory
authors.affiliation: Division of Hematology-Oncology, Department of Pediatrics, Weill Cornell Medical College, New York, NY 10021, USA; Division of Hematology-Oncology, Department of Cell and Biology Development, Weill Cornell Medical College, New York, NY 10021, USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Rivella
authors.affiliation: Laboratory of Cellular and Developmental Biology, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ann
authors.initials: A
authors.lastname: Dean
authors.affiliation: Division of Hematology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA; The Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. Electronic address: blobel@email.chop.edu.
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Blobel
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000378:metabolism; D004900:Erythroblasts / Q000378:metabolism; D005319:Fetal Hemoglobin / Q000235:genetics*; D005821:Genetic Techniques; D006453:Hemoglobinopathies / Q000235:genetics / Q000628:therapy; D006801:Humans; D019901:Locus Control Region; D051379:Mice; D061251:Primary Cell Culture; D015533:Transcriptional Activation; D055544:beta-Globins / Q000235:genetics*
chemical_list: D018952:Antigens, CD34; D002843:Chromatin; D055544:beta-Globins; D005319:Fetal Hemoglobin