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

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Science  19 Dec 2008:
Vol. 322, Issue 5909, pp. 1839-1842
DOI: 10.1126/science.1165409
  • Fig. 1.

    Analysis of BCL11A expression in human erythroid progenitors. (A) A Western blot showing the major isoforms, XL and L, from nuclear extracts of human erythroid cells [cultured and isolated as described in (11)]. These two isoforms, which were confirmed by reverse transcription polymerase chain reaction (RT-PCR) of all known and predicted exons, are depicted. (B) The common variant rs4671393 is associated with BCL11A expression in human lymphoblastoid cell lines from the HapMap CEU and YRI populations. Quantitative RT-PCR (qRT-PCR) was performed on RNA from these cell lines and normalized to the level of human β-actin (5, 3, and 3, from left to right). Results are means ± SEM. Significance of differences between genotypes was calculated using the Student's t test. (C) Western blots of lysates of primary human bone marrow (BM) erythroblasts, second-trimester FL erythroblasts, first-trimester circulating primitive erythroblasts, and K562 cells. Primary human stage–matched erythroblasts were isolated by sorting for the CD235 and CD71 double-positive population. The XL and L bands migrate together here as a result of reduced separation on this blot.

  • Fig. 2.

    Proteomic affinity screen identifies BCL11A partner proteins in erythroid cells. (A) The scheme used for the affinity-purification in mouse erythroleukemia (MEL) cells is depicted in this diagram. Once FLAG peptide elution was performed, whole-lane mass spectrometry from acrylamide gels was done as described in (11). We used a subtractive approach, including a simultaneous pull-down in parental Mel-BirA (MB) cells. (B) The results of this subtractive screen are shown with the number of peptides obtained in each trial listed adjacent to the identified protein. The components of the NuRD complex are shown in blue. (C) Confirmation of interactions of BCL11A with GATA-1, FOG-1, MTA2, and RBBP7 in erythroid (MEL) cells (FBB is the cell line containing tagged BCL11A). BCL11A interactions with GATA-1 (D) and FOG-1 (E) could be confirmed by exogenous expression in COS-7 cells by using FLAG-tagged versions of GATA-1 or FOG-1 and V5-tagged versions of BCL11A. (F) Using this same strategy in 293T cells, fragments of GATA-1 (all of which show robust expression here) could be used to map the interaction with BCL11A. The structure of GATA-1 is shown on the right side, including the N-terminal domain (ND), the N-terminal zinc finger (NF), and the C-terminal zinc finger (CF).

  • Fig. 3.

    BCL11A acts as a silencer of γ-globin gene expression, based on modulation of BCL11A levels. (A) siRNA-mediated knockdown of BCL11A results in elevations of γ-globin mRNA levels (as a percentage of total β-like globin gene expression) in human erythroid progenitor cells at day 7 of differentiation in comparison with NT control siRNAs. (B) Microarray profiling of these cells using the Affymetrix U133 Plus 2.0 array reveals that there is close similarity in the expression profile of NT and BCL11A siRNA-treated cells (r2 = 0.9901). Microarray data processing and filtering were performed as described previously (27) and in (11). (C) Lentiviral-mediated shRNA delivery to human erythroid progenitors results in robust knockdown of BCL11A protein. Control samples were infected with lentivirus prepared from the backbone pLKO.1ps vector. (D) At day 6 of differentiation, the cells appear to be morphologically indistinguishable; this is also the case at other stages of differentiation. (E) The shRNA-mediated knockdown of BCL11A results in robust induction of γ-globin mRNA level on day 7 of differentiation (***P < 10–5 in comparison with control). (F) Hemolysates prepared from cells on day 12 of differentiation show the presence of mature HbF by hemoglobin HPLC. The HbF peaks are labeled with an arrow in each chromatogram, with the first peak corresponding to acetylated HbF (28) and the second unmodified HbF. All results are means ± SEM. Statistical significance was calculated using the Student's t test.

  • Fig. 4.

    BCL11A occupies discrete regions in the human β-globin locus in adult erythroid progenitors. The human β-globin locus is depicted at the top with regions showing significant binding shaded in gray in the histogram plot below. The results are means ± SD (n = 3 per group).

Additional Files

  • Human Fetal Hemoglobin Expression Is Regulated by the Developmental Stage-Specific Repressor BCL11A
    Vijay G. Sankaran, Tobias F. Menne, Jian Xu, Thomas E. Akie, Guillaume Lettre, Ben Van Handel, Hanna K.A. Mikkola, Joel N. Hirschhorn, Alan B. Cantor, Stuart H. Orkin

    Supporting Online Material

    This supplement contains:
    Materials and Methods
    Figs. S1 to S4

    This file is in Adobe Acrobat PDF format.

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