title: Forced chromatin looping raises fetal hemoglobin in adult sickle cells to higher levels than pharmacologic inducers.
abstract: Overcoming the silencing of the fetal γ-globin gene has been a long-standing goal in the treatment of sickle cell disease (SCD). The major transcriptional enhancer of the β-globin locus, called the locus control region (LCR), dynamically interacts with the developmental stage-appropriate β-type globin genes via chromatin looping, a process requiring the protein Ldb1. In adult erythroid cells, the LCR can be redirected from the adult β- to the fetal γ-globin promoter by tethering Ldb1 to the human γ-globin promoter with custom-designed zinc finger (ZF) proteins (ZF-Ldb1), leading to reactivation of γ-globin gene expression. To compare this approach to pharmacologic reactivation of fetal hemoglobin (HbF), hematopoietic cells from patients with SCD were treated with a lentivirus expressing the ZF-Ldb1 or with chemical HbF inducers. The HbF increase in cells treated with ZF-Ldb1 was more than double that observed with decitabine and pomalidomide; butyrate had an intermediate effect whereas tranylcypromine and hydroxyurea showed relatively low HbF reactivation. ZF-Ldb1 showed comparatively little toxicity, and reduced sickle hemoglobin (HbS) synthesis as well as sickling of SCD erythroid cells under hypoxic conditions. The efficacy and low cytotoxicity of lentiviral-mediated ZF-Ldb1 gene transfer compared with the drug regimens support its therapeutic potential for the treatment of SCD.
authors.affiliation: Department of Pediatrics, Division of Hematology-Oncology, Children's Blood and Cancer Foundation Laboratories, Weill Cornell Medical College, New York, NY; Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Laura
authors.identifier: 0000-0003-2133-4432
authors.initials: L
authors.lastname: Breda
authors.affiliation: Department of Pediatrics, Division of Hematology-Oncology, Children's Blood and Cancer Foundation Laboratories, Weill Cornell Medical College, New York, NY; Department of Clinical Science and Community Health, University of Milan, Milan, Italy;
authors.forename: Irene
authors.initials: I
authors.lastname: Motta
authors.affiliation: Department of Pediatrics, Division of Hematology-Oncology, Children's Blood and Cancer Foundation Laboratories, Weill Cornell Medical College, New York, NY; Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Silvia
authors.initials: S
authors.lastname: Lourenco
authors.affiliation: Department of Pediatrics, Division of Hematology-Oncology, Children's Blood and Cancer Foundation Laboratories, Weill Cornell Medical College, New York, NY;
authors.forename: Chiara
authors.initials: C
authors.lastname: Gemmo
authors.affiliation: Transcription Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA; and.
authors.forename: Wulan
authors.initials: W
authors.lastname: Deng
authors.affiliation: Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Rupon
authors.affiliation: Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Osheiza Y
authors.initials: OY
authors.lastname: Abdulmalik
authors.affiliation: Department of Pediatrics, Albert Einstein College of Medicine, Children's Hospital at Montefiore, Bronx, NY.
authors.forename: Deepa
authors.initials: D
authors.lastname: Manwani
authors.affiliation: Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Gerd A
authors.initials: GA
authors.lastname: Blobel
authors.affiliation: Department of Pediatrics, Division of Hematology-Oncology, Children's Blood and Cancer Foundation Laboratories, Weill Cornell Medical College, New York, NY; Department of Pediatrics, Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Stefano
authors.initials: S
authors.lastname: Rivella
mesh_terms: D000328:Adult; D000755:Anemia, Sickle Cell / Q000378:metabolism*; D018952:Antigens, CD34 / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins; D041905:Erythroid Cells / Q000378:metabolism; D005319:Fetal Hemoglobin / Q000378:metabolism*; D006451:Hemoglobin, Sickle; D006801:Humans; D060588:LIM Domain Proteins; D014157:Transcription Factors; D016335:Zinc Fingers
chemical_list: D018952:Antigens, CD34; D002843:Chromatin; D004268:DNA-Binding Proteins; D006451:Hemoglobin, Sickle; C486312:LDB1 protein, human; D060588:LIM Domain Proteins; D014157:Transcription Factors; D005319:Fetal Hemoglobin