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A natural regulatory mutation in the proximal promoter elevates fetal globin expression by creating a de novo GATA1 site

Gabriella E. Martyn, Beeke Wienert, Ryo Kurita, Yukio Nakamura, Kate G.R. Quinlan and Merlin Crossley

Key points

  • Introducing the -113A>G Hereditary Persistence of Fetal Hemoglobin (HPFH) mutation into erythroid cells elevates fetal globin levels.

  • The -113A>G mutation creates a de novo site for the activator GATA1 but does not disrupt binding of fetal globin repressor BCL11A.

Abstract

β-hemoglobinopathies, such as sickle cell disease and β-thalassemia result from mutations in the adult β-globin gene. Reactivating the developmentally silenced fetal γ-globin gene elevates fetal hemoglobin levels and ameliorates symptoms of β-hemoglobinopathies. The continued expression of fetal γ-globin into adulthood occurs naturally in a genetic condition termed Hereditary Persistence of Fetal Hemoglobin (HPFH). Point mutations in the fetal γ-globin proximal promoter can cause HPFH. The -113A>G HPFH mutation falls within the -115 cluster of HPFH mutations, a binding site for the fetal globin repressor BCL11A. We demonstrate that the -113A>G HPFH mutation, unlike other mutations in the cluster, does not disrupt BCL11A binding but rather creates a de novo binding site for the transcriptional activator GATA1. Introduction of the -113A>G HPFH mutation into erythroid cells using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) system increases GATA1 binding and elevates fetal globin levels. These results reveal the mechanism by which the -113A>G HPFH mutation elevates fetal globin and demonstrate the sensitivity of the fetal globin promoter to point mutations that often disrupt repressor binding sites but here create a de novo site for an erythroid activator.

  • Submitted July 16, 2018.
  • Accepted December 18, 2018.