Lineage-specific BCL11A Knockdown Circumvents Toxicities and Reverses Sickle Phenotype

J Clin Invest. 2016 Oct 3;126(10):3868-3878. doi: 10.1172/JCI87885. Epub 2016 Sep 6.

Abstract

Reducing expression of the fetal hemoglobin (HbF) repressor BCL11A leads to a simultaneous increase in γ-globin expression and reduction in β-globin expression. Thus, there is interest in targeting BCL11A as a treatment for β-hemoglobinopathies, including sickle cell disease (SCD) and β-thalassemia. Here, we found that using optimized shRNAs embedded within an miRNA (shRNAmiR) architecture to achieve ubiquitous knockdown of BCL11A profoundly impaired long-term engraftment of both human and mouse hematopoietic stem cells (HSCs) despite a reduction in nonspecific cellular toxicities. BCL11A knockdown was associated with a substantial increase in S/G2-phase human HSCs after engraftment into immunodeficient (NSG) mice, a phenotype that is associated with HSC exhaustion. Lineage-specific, shRNAmiR-mediated suppression of BCL11A in erythroid cells led to stable long-term engraftment of gene-modified cells. Transduced primary normal or SCD human HSCs expressing the lineage-specific BCL11A shRNAmiR gave rise to erythroid cells with up to 90% reduction of BCL11A protein. These erythrocytes demonstrated 60%-70% γ-chain expression (vs. < 10% for negative control) and a corresponding increase in HbF. Transplantation of gene-modified murine HSCs from Berkeley sickle cell mice led to a substantial improvement of sickle-associated hemolytic anemia and reticulocytosis, key pathophysiological biomarkers of SCD. These data form the basis for a clinical trial application for treating sickle cell disease.

MeSH terms

  • Anemia, Sickle Cell / therapy*
  • Animals
  • Antigens, CD34 / metabolism
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cell Lineage
  • Cells, Cultured
  • Gene Knockdown Techniques
  • Genetic Therapy
  • Graft vs Host Disease / prevention & control
  • Hematopoiesis*
  • Hematopoietic Stem Cell Transplantation
  • Hematopoietic Stem Cells / physiology
  • Humans
  • Mice, Inbred C57BL
  • Mice, Inbred NOD
  • Mice, SCID
  • Nuclear Proteins / genetics*
  • Nuclear Proteins / metabolism
  • Phenotype
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Repressor Proteins

Substances

  • Antigens, CD34
  • BCL11A protein, human
  • Carrier Proteins
  • Nuclear Proteins
  • RNA, Small Interfering
  • Repressor Proteins