Human Fetal Hemoglobin Expression Is Regulated by the Developmental Stage-Specific Repressor BCL11A

Division of Hematology/Oncology, Children's Hospital Boston, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115, USA.
Science (Impact Factor: 33.61). 01/2009; 322(5909):1839-42. DOI: 10.1126/science.1165409
Source: PubMed


Differences in the amount of fetal hemoglobin (HbF) that persists into adulthood affect the severity of sickle cell disease
and the β-thalassemia syndromes. Genetic association studies have identified sequence variants in the gene BCL11A that influence HbF levels. Here, we examine BCL11A as a potential regulator of HbF expression. The high-HbF BCL11A genotype is associated with reduced BCL11A expression. Moreover, abundant expression of full-length forms of BCL11A is developmentally restricted to adult erythroid cells. Down-regulation of BCL11A expression in primary adult erythroid cells leads to robust HbF expression. Consistent with a direct role of BCL11A in globin gene regulation, we find that BCL11A occupies several discrete sites in the β-globin gene cluster. BCL11A emerges as a therapeutic target for reactivation of HbF in β-hemoglobin disorders.

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Available from: Ben Van Handel, Jul 03, 2014
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    • "As a result, significant knowledge regarding the molecular mechanisms underlying HbF regulation has been uncovered. For instance, gene linkage studies associated BCL11A, HSB1L-MYB and HBB regions in the genome with increased HbF expression in adults [6]–[9], and suppression of BCL11A causes an increase in HbF levels and reverses the SCD phenotype in model systems [10], [11]. "
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    ABSTRACT: Induction of fetal hemoglobin (HbF) has therapeutic importance for patients with sickle cell disease (SCD) and the beta-thalassemias. It was recently reported that increased expression of LIN28 proteins or decreased expression of its target let-7 miRNAs enhances HbF levels in cultured primary human erythroblasts from adult healthy donors. Here LIN28A effects were studied further using erythrocytes cultured from peripheral blood progenitor cells of pediatric subjects with SCD. Transgenic expression of LIN28A was accomplished by lentiviral transduction in CD34(+) sickle cells cultivated ex vivo in serum-free medium. LIN28A over-expression (LIN28A-OE) increased HbF, reduced beta (sickle)-globin, and strongly suppressed all members of the let-7 family of miRNAs. LIN28A-OE did not affect erythroblast differentiation or prevent enucleation, but it significantly reduced or ameliorated the sickling morphologies of the enucleated erythrocytes.
    PLoS ONE 09/2014; 9(9):e106924. DOI:10.1371/journal.pone.0106924 · 3.23 Impact Factor
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    • "A variety of nuclear complexes contribute to the silencing of the embryonic and fetal globin genes in adult erythroid cells (Sankaran et al., 2010). Among these, arguably the most powerful one is nucleated by Bcl11a (Sankaran et al., 2008, 2009), which does not bind directly to promoters of the silenced human fetal globin genes but seems to repress them via a mechanism involving higher-order chromatin looping (Kiefer et al., 2011; Xu et al., 2010). Hence, manipulating chromatin loops might be a viable strategy to reverse the globin switch. "
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    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.
    Cell 08/2014; 158(4):849-60. DOI:10.1016/j.cell.2014.05.050 · 32.24 Impact Factor
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    • "Although transcription factors were detected they were clearly underrepresented, for example BCL11A and KLF1 were absent. As these two transcription factors are essential for adult globin expression [24], [25], [26], and the latter for regulating the expression of many erythroid genes [27], [28], we compared their expression in PB, CB and iPSC C19 erythroid cells at day 8 in culture by western blot (Figure 5). BCL11A was detected in both PB and, at a lower level in CB but was not detected in the C19 cells. "
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    ABSTRACT: Induced pluripotent stem cells (iPSC) are an attractive progenitor source for the generation of in vitro blood products. However, before iPSC-derived erythroid cells can be considered for therapeutic use their similarity to adult erythroid cells must be confirmed. We have analysed the proteome of erythroid cells differentiated from the iPSC fibroblast derived line (C19) and showed they express hallmark RBC proteins, including all those of the ankyrin and 4.1R complex. We next compared the proteome of erythroid cells differentiated from three iPSC lines (C19, OCE1, OPM2) with that of adult and cord blood progenitors. Of the 1989 proteins quantified <3% differed in level by 2-fold or more between the different iPSC-derived erythroid cells. When compared to adult cells, 11% of proteins differed in level by 2-fold or more, falling to 1.9% if a 5-fold threshold was imposed to accommodate slight inter-cell line erythropoietic developmental variation. Notably, the level of >30 hallmark erythroid proteins was consistent between the iPSC lines and adult cells. In addition, a sub-population (10-15%) of iPSC erythroid cells in each of the iPSC lines completed enucleation. Aberrant expression of some cytoskeleton proteins may contribute to the failure of the majority of the cells to enucleate since we detected some alterations in cytoskeletal protein abundance. In conclusion, the proteome of erythroid cells differentiated from iPSC lines is very similar to that of normal adult erythroid cells, but further work to improve the induction of erythroid cells in existing iPSC lines or to generate novel erythroid cell lines is required before iPSC-derived red cells can be considered suitable for transfusion therapy.
    PLoS ONE 07/2014; 9(7):e100874. DOI:10.1371/journal.pone.0100874 · 3.23 Impact Factor
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