Inhibition of G9a methyltransferase stimulates fetal hemoglobin production by facilitating LCR/γ-globin looping

Blood. 2015 Jul 30;126(5):665-72. doi: 10.1182/blood-2015-02-629972. Epub 2015 May 15.

Abstract

Induction of fetal hemoglobin (HbF) production in adult erythrocytes can reduce the severity of sickle cell disease and β-thalassemia. Transcription of β-globin genes is regulated by the distant locus control region (LCR), which is brought into direct gene contact by the LDB1/GATA-1/TAL1/LMO2-containing complex. Inhibition of G9a H3K9 methyltransferase by the chemical compound UNC0638 activates fetal and represses adult β-globin gene expression in adult human hematopoietic precursor cells, but the underlying mechanisms are unclear. Here we studied UNC0638 effects on β-globin gene expression using ex vivo differentiation of CD34(+) erythroid progenitor cells from peripheral blood of healthy adult donors. UNC0638 inhibition of G9a caused dosed accumulation of HbF up to 30% of total hemoglobin in differentiated cells. Elevation of HbF was associated with significant activation of fetal γ-globin and repression of adult β-globin transcription. Changes in gene expression were associated with widespread loss of H3K9me2 in the locus and gain of LDB1 complex occupancy at the γ-globin promoters as well as de novo formation of LCR/γ-globin contacts. Our findings demonstrate that G9a establishes epigenetic conditions preventing activation of γ-globin genes during differentiation of adult erythroid progenitor cells. In this view, manipulation of G9a represents a promising epigenetic approach for treatment of β-hemoglobinopathies.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Anemia, Sickle Cell / blood
  • Anemia, Sickle Cell / drug therapy
  • Anemia, Sickle Cell / genetics
  • Cell Differentiation
  • DNA-Binding Proteins / blood
  • Enzyme Inhibitors / pharmacology
  • Epigenesis, Genetic / drug effects
  • Erythroid Precursor Cells / cytology
  • Erythroid Precursor Cells / drug effects
  • Erythroid Precursor Cells / metabolism
  • Erythropoiesis
  • Fetal Hemoglobin / biosynthesis*
  • Histocompatibility Antigens
  • Histone-Lysine N-Methyltransferase / antagonists & inhibitors*
  • Humans
  • In Vitro Techniques
  • LIM Domain Proteins / blood
  • Locus Control Region*
  • Models, Biological
  • Promoter Regions, Genetic
  • Quinazolines / pharmacology
  • Transcription Factors / blood
  • beta-Thalassemia / blood
  • beta-Thalassemia / drug therapy
  • beta-Thalassemia / genetics
  • gamma-Globins / genetics*

Substances

  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Histocompatibility Antigens
  • LDB1 protein, human
  • LIM Domain Proteins
  • Quinazolines
  • Transcription Factors
  • UNC 0638
  • gamma-Globins
  • Fetal Hemoglobin
  • EHMT2 protein, human
  • Histone-Lysine N-Methyltransferase