Statistical Evidence for the Existence of a Regulatory Mechanism That Balances α-Globin and AHSP Expression in Erythroid Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1775-1775
Author(s):  
Maria Elena Fabucci ◽  
Katija Jelicic ◽  
Elena Alfani ◽  
Anna Rita F. Migliaccio
Keyword(s):  
Gene Expression ◽  
Regulatory Mechanism ◽  
Globin Gene ◽  
Statistical Analyses ◽  
Globin Genes ◽  
Erythroid Cells ◽  
Globin Mrna ◽  
Donor Variability ◽  
In Erythroid Cells

Abstract Alpha haemoglobin stabilizing protein (AHSP) is encoded by a gene abundantly expressed in erythroid cells whose function is to chaperone α-chains in the process of haemoglobin assembly (Yu et al, JCI2007; 117:1856). The central role of the excess of α-chains in the pathogenesis of β-thalassemia and the AHSP ability to limit the toxicity of excessive α-globin suggest that increases of AHSP expression might ameliorate the clinical phenotype of β-thalassemia. To clarify the relationship between AHSP and globin gene expression, we measured the levels of mRNA for these genes in erythroblasts generated in vitro from the blood of 30 normal donors and 8 β-thalassemic patients. Normal erythroblasts presented a marked donor-to-donor variability in the expression levels of all the genes analysed. Inter-quartile range (IQR) analyses indicates that the gene whose expression has the highest variability is α-globin (IQR=31.5), followed by β-globin (IQR=8.74), AHSP (IQR=2.82) and γ-globin (IQR=0.86). The IQR value for the α/non-α globin ratio (1.91) is higher than that of the γ/γ+β ratio (0.11), an indication of the existence of donor variegation in the levels of unbalance between expression of α- and non-α globin genes in cells from different donors. The extent of this variegation is even more apparent by the high IQR level of the α-(non-α) expression difference (IQR=38.6). β-thalassemic erythroblasts expressed normal levels of α- and γ-globin, significantly (P<.05) lower levels of β-globin mRNA and, surprisingly, high levels (by 10-fold) of AHSP mRNA. Subject-variability in gene expression was also observed for β-thalassemic erythroblasts. In this case, the gene whose expression had the highest variability is AHSP (IQR=42.8), followed by α-globin (IQR=11.75), β-globin (IQR=3.32), and γ-globin (IQR=1.74). The IQR for the α/non-α globin ratio (7.2) is higher than that of the γ/γ+β ratio (0.67) also for β-thalassemic erythroblasts. The difference between the variances of the excess of α-expression [α-(non-α)] in β-thalassemic and normal erythroblasts is significant by F test (P=.0023). Statistical analyses of these results indicates that, as expected, the levels of α-globin mRNA are positively correlated to those of the non-α globin genes in normal erythroblasts (R2=.93, P<.001) but not in β-thalassemic cells (R2=.22, P<.24). In contrast, the levels of α-globin mRNA are positively correlated with those of AHSP both in normal (R2=.86, P<.0001) and β-thalassemic (R2=.66, P<.05) erythroblasts. Moreover, in spite of the fact that expression of α-globin is correlated, at least in normal erythroblasts, with that of γ+β mRNA, no correlation is found between levels of AHSP mRNA and those of γ+β mRNA. No correlation is also observed between levels of AHSP mRNA and the α/non-α ratio. In contrast, the levels of AHSP mRNA are correlated with the levels of excess of α-globin mRNA in normal erythroblasts (R2=0.86, P<.0001) and the fact that are not correlated in β-thalassemic cells (R2=.45, P=.066) might be due to the limited experimental points available for analyses. In conclusion, this statistical analyses provides evidence for the existence of a regulatory mechanism that balances expression of AHSP with that of excess of α-globin mRNA in erythroid cells. It is suggested that this regulatory mechanism may represent a target for eventual gene modifiers of the β-thalassemic trait. MEF is the recipient of a Marie Curie training Network Fellowship from EU.

scholarly journals Substitution of the Human β-Spectrin Promoter for the Human Aγ-Globin Promoter Prevents Silencing of a Linked Human β-Globin Gene in Transgenic Mice

1998 ◽  
Vol 18 (11) ◽  
pp. 6634-6640 ◽  
Author(s):  
Denise E. Sabatino ◽  
Amanda P. Cline ◽  
Patrick G. Gallagher ◽  
Lisa J. Garrett ◽  
George Stamatoyannopoulos ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Fetal Liver ◽  
Globin Gene ◽  
Gene Promoter ◽  
Yolk Sac ◽  
Globin Genes ◽  
Erythroid Cells ◽  
Globin Mrna ◽  
Globin Promoter ◽  
In Erythroid Cells

ABSTRACT During development, changes occur in both the sites of erythropoiesis and the globin genes expressed at each developmental stage. Previous work has shown that high-level expression of human β-like globin genes in transgenic mice requires the presence of the locus control region (LCR). Models of hemoglobin switching propose that the LCR and/or stage-specific elements interact with globin gene sequences to activate specific genes in erythroid cells. To test these models, we generated transgenic mice which contain the human Aγ-globin gene linked to a 576-bp fragment containing the human β-spectrin promoter. In these mice, the β-spectrin Aγ-globin (βsp/Aγ) transgene was expressed at high levels in erythroid cells throughout development. Transgenic mice containing a 40-kb cosmid construct with the micro-LCR, βsp/Aγ-, ψβ-, δ-, and β-globin genes showed no developmental switching and expressed both human γ- and β-globin mRNAs in erythroid cells throughout development. Mice containing control cosmids with the Aγ-globin gene promoter showed developmental switching and expressed Aγ-globin mRNA in yolk sac and fetal liver erythroid cells and β-globin mRNA in fetal liver and adult erythroid cells. Our results suggest that replacement of the γ-globin promoter with the β-spectrin promoter allows the expression of the β-globin gene. We conclude that the γ-globin promoter is necessary and sufficient to suppress the expression of the β-globin gene in yolk sac erythroid cells.

scholarly journals ZNF410 uniquely activates the NuRD component CHD4 to silence fetal hemoglobin expression

2020 ◽  
Author(s):  
Xianjiang Lan ◽  
Ren Ren ◽  
Ruopeng Feng ◽  
Lana C. Ly ◽  
Yemin Lan ◽  
...  
Keyword(s):  
Dna Binding ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Erythroid Cell ◽  
List Type ◽  
Globin Genes ◽  
Erythroid Cells ◽  
Adult Type ◽  
In Erythroid Cells

SummaryMetazoan transcription factors typically regulate large numbers of genes. Here we identify via a CRISPR-Cas9 genetic screen ZNF410, a pentadactyl DNA binding protein that in human erythroid cells directly and measurably activates only one gene, the NuRD component CHD4. Specificity is conveyed by two highly evolutionarily conserved clusters of ZNF410 binding sites near the CHD4 gene with no counterparts elsewhere in the genome. Loss of ZNF410 in adult-type human erythroid cell culture systems and xenotransplant settings diminishes CHD4 levels and derepresses the fetal hemoglobin genes. While previously known to be silenced by CHD4, the fetal globin genes are exposed here as among the most sensitive to reduced CHD4 levels. In vitro DNA binding assays and crystallographic studies reveal the ZNF410-DNA binding mode. ZNF410 is a remarkably selective transcriptional activator in erythroid cells whose perturbation might offer new therapeutic opportunities in the treatment of hemoglobinopathies.HighlightsA CRISPR screen implicates ZNF410 in fetal globin gene repressionThe CHD4 gene is the singular direct ZNF410 target in erythroid cellsThe fetal globin genes are exquisitely sensitive to CHD4 levelsFive C2H2 zinc fingers of ZNF410 recognize the major groove of a 14 base pair sequence

scholarly journals ZNF410 Uniquely Activates the NuRD Component CHD4 to Silence Fetal Hemoglobin Expression

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 54-54
Author(s):  
Xianjiang Lan ◽  
Ren Ren ◽  
Ruopeng Feng ◽  
Lana C Ly ◽  
Yemin Lan ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Dna Binding ◽  
Target Gene ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Globin Genes ◽  
Erythroid Cells ◽  
Private Company ◽  
In Erythroid Cells

Transcription factors typically regulate a large number of genes. Here we found that transcription factor ZNF410 binds and activates the expression of a single direct target gene, CHD4, to enforce the silencing of the fetal hemoglobin genes (HBG1 and HBG2) in adult erythroid cells. ZNF410 is a pentadactyl DNA binding protein that emerged from a DNA binding domain-focused CRISPR-Cas9 screen aimed at the identification of new regulators of fetal hemoglobin silencing. Depletion of ZNF410 specifically diminished CHD4 expression, leading to reactivation of the normally silent fetal globin genes in both human erythroid culture systems and a human-to-mouse xenotransplant model. Combining RNA-seq and ChIP-seq analyses revealed that CHD4 is the sole direct ZNF410 target gene in erythroid cells, which was further validated by rescue of fetal hemoglobin silencing and other transcriptional changes upon CHD4 restoration in ZNF410-deficient cells. ZNF410 ChIP-seq detected only eight high-confidence peaks with seven associated genes including CHD4. Most strikingly, the two most predominant peaks are located at the CHD4 locus, which contains two highly conserved, dense clusters of ZNF410 binding motifs. The two motif clusters appear to be unique in the human and mouse genomes. Moreover, among the seven ZNF410-bound genes, CHD4 was the only one whose expression was down-regulated upon ZNF410 depletion, indicating that CHD4 is the sole target of ZNF410. Electrophoretic mobility shift assays (EMSAs) showed that the zinc finger (ZF) domain of ZNF410 is necessary and sufficient for DNA binding. When overexpressed, the DNA binding profile of ZF domain alone is very similar to full length ZNF410. Indeed, forced expression of the ZF domain displaced endogenous ZNF410 at all binding sites, including the CHD4 locus. This reduced CHD4 expression to levels comparable to those in ZNF410 deficient cells (and activated the fetal globin genes) but had no effect on the other ZNF410 bound genes, again confirming target specificity. ZNF410 depletion or expression of the dominant negative acting ZF domain lowered CHD4 only by ~65%-70%, which is very well tolerated by erythroid cells, as determined by morphology, cell surface phenotyping, and gene expression profiling. This exposes the fetal globin genes as highly sensitive to CHD4 levels. Lastly, we solved the crystal structure of the ZF domain-DNA complex at 2.75Å resolution pinpointing the protein-DNA contacts and showing that each of the five ZFs make specific DNA contacts. In sum, to our knowledge, ZNF410 is the only transcription factor with just one direct functional target gene in erythroid cells. Given the strong impetus to reactivate fetal globin gene expression in patients with sickle cell disease and some forms of b-thalassemia, it might be possible to exploit the exceptionally high transcriptional selectivity of ZNF410 to raise fetal hemoglobin expression for the treatment of these hemoglobinopathies. Disclosures Weiss: Rubius Inc.: Consultancy, Current equity holder in private company; Cellarity Inc.: Consultancy, Current equity holder in private company; Novartis: Consultancy, Current equity holder in private company; Esperion Therapeutics: Consultancy, Current equity holder in private company; Beam Therapeuticcs: Consultancy, Current equity holder in private company. Blobel:Fulcrum Therapeutics: Consultancy; Pfizer: Research Funding.

scholarly journals Mi2β-mediated silencing of the fetal γ-globin gene in adult erythroid cells

Blood ◽  
2013 ◽  
Vol 121 (17) ◽  
pp. 3493-3501 ◽  
Author(s):  
Maria Amaya ◽  
Megha Desai ◽  
Merlin Nithya Gnanapragasam ◽  
Shou Zhen Wang ◽  
Sheng Zu Zhu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Major Part ◽  
Globin Gene ◽  
Globin Genes ◽  
Erythroid Cells ◽  
Key Points ◽  
Globin Gene Expression ◽  
Partial Depletion

Key Points Mi2β exerts a major part of its silencing effect on embryonic and fetal globin genes by positively regulating the BCL11A and KLF1 genes. Partial depletion of Mi2β induces increased γ-globin gene expression in primary human erythroid cells without impairing differentiation.

scholarly journals AUF-1 and YB-1 are critical determinants of β-globin mRNA expression in erythroid cells

Blood ◽  
2012 ◽  
Vol 119 (4) ◽  
pp. 1045-1053 ◽  
Author(s):  
Sebastiaan van Zalen ◽  
Grace R. Jeschke ◽  
Elizabeth O. Hexner ◽  
J. Eric Russell
Keyword(s):  
Posttranscriptional Regulation ◽  
Rna Binding ◽  
Globin Gene ◽  
K562 Cells ◽  
Erythroid Cells ◽  
Erythroid Progenitors ◽  
Globin Mrna ◽  
Affinity Enrichment

Abstract The normal accumulation of β-globin protein in terminally differentiating erythroid cells is critically dependent on the high stability of its encoding mRNA. The molecular basis for this property, though, is incompletely understood. Factors that regulate β-globin mRNA within the nucleus of early erythroid progenitors are unlikely to account for the constitutively high half-life of β-globin mRNA in the cytoplasm of their anucleate erythroid progeny. We conducted in vitro protein-RNA binding analyses that identified a cytoplasm-restricted β-globin messenger ribonucleoprotein (mRNP) complex in both cultured K562 cells and erythroid-differentiated human CD34+ cells. This novel mRNP targets a specific guanine-rich pentanucleotide in a region of the β-globin 3′untranslated region that has recently been implicated as a determinant of β-globin mRNA stability. Subsequent affinity-enrichment analyses identified AUF-1 and YB-1, 2 cytoplasmic proteins with well-established roles in RNA biology, as trans-acting components of the mRNP. Factor-depletion studies conducted in vivo demonstrated the importance of the mRNP to normal steady-state levels of β-globin mRNA in erythroid precursors. These data define a previously unrecognized mechanism for the posttranscriptional regulation of β-globin mRNA during normal erythropoiesis, providing new therapeutic targets for disorders of β-globin gene expression.

scholarly journals Developmental- and differentiation-specific patterns of human γ- and β-globin promoter DNA methylation

Blood ◽  
2007 ◽  
Vol 110 (4) ◽  
pp. 1343-1352 ◽  
Author(s):  
Rodwell Mabaera ◽  
Christine A. Richardson ◽  
Kristin Johnson ◽  
Mei Hsu ◽  
Steven Fiering ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Promoter Methylation ◽  
Fetal Liver ◽  
Globin Gene ◽  
Erythroid Cells ◽  
Promoter Dna Methylation ◽  
Globin Promoter ◽  
Promoter Dna

AbstractThe mechanisms underlying the human fetal-to-adult β-globin gene switch remain to be determined. While there is substantial experimental evidence to suggest that promoter DNA methylation is involved in this process, most data come from studies in nonhuman systems. We have evaluated human γ- and β-globin promoter methylation in primary human fetal liver (FL) and adult bone marrow (ABM) erythroid cells. Our results show that, in general, promoter methylation and gene expression are inversely related. However, CpGs at −162 of the γ promoter and −126 of the β promoter are hypomethylated in ABM and FL, respectively. We also studied γ-globin promoter methylation during in vitro differentiation of erythroid cells. The γ promoters are initially hypermethylated in CD34+ cells. The upstream γ promoter CpGs become hypomethylated during the preerythroid phase of differentiation and are then remethylated later, during erythropoiesis. The period of promoter hypomethylation correlates with transient γ-globin gene expression and may explain the previously observed fetal hemoglobin production that occurs during early adult erythropoiesis. These results provide the first comprehensive survey of developmental changes in human γ- and β-globin promoter methylation and support the hypothesis that promoter methylation plays a role in human β-globin locus gene switching.

5-Azacytidine Induction of Human γ-Globin Gene Expression: Experimental Evaluation of Current Models.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1581-1581
Author(s):  
Rodwell Mabaera ◽  
Christine Richardson ◽  
Sarah Conine ◽  
Christopher H. Lowrey
Keyword(s):  
Gene Expression ◽  
Globin Gene ◽  
Erythroid Differentiation ◽  
Maximal Response ◽  
Mrna Levels ◽  
Erythroid Cells ◽  
Globin Mrna ◽  
Potent Inducer ◽  
Cellular Dna ◽  
Globin Gene Expression

Abstract 5-Azacytidine (5-Aza) was demonstrated to be a potent inducer of human fetal globin gene expression more than 20 years ago. More recently, 5-Aza-2-deoxycytidine has been shown to have similar properties. Since the 1980’s there have been two predominant hypotheses to explain the action of these agents. The first is based on the observation that these, and several other active inducing agents, are cytotoxic to differentiating erythroid cells and that drug treatment alters the kinetics of erythroid differentiation. This has been proposed to result in prolonged expression of the γ-globin genes which are normally expressed only early in differentiation. The second is based on the observation that both agents are DNA methyltransferase inhibitors and are presumed to cause demethylation of cellular DNA including the γ-globin gene promoters leading to activation of the genes. These two models lead to specific predictions that we have evaluated using an in vitro erythroid differentiation system. In this system, human adult CD34+ cells are cultured in SCF, Flt3 ligand and IL-3 for 7 days and then switched to Epo for 14 days. This results in an exponential expansion of erythroid cells. As has been described for normal human differentiation, these cells express small amounts of γ-globin mRNA early in differentiation followed by a much larger amount of β-globin mRNA. HPLC at the end of the culture period shows 99% HbA and 1% HbF. Treatment of cultures on a daily basis with 5-Aza starting on day 10 results in dose dependent increases in γ-globin mRNA, Gγ- and Aγ-chain production and HbF. The cytotoxicity model predicts that γ-globin expression will be prolonged to later in differentiation - and this is seen. However, a daily 5-Aza dose of 300 nM, which produces ~80% of the maximal response in γ-globin mRNA and HbF, has no effect on cell growth or differentiation kinetics. This argues against the toxicity model. We next examined the effect of 5-Aza on γ-globin promoter methylation using the bisulfite method. We studied CpGs at −344, −252, −162, −53, −50, +6, +19 and +50 relative to the start site. For untreated controls, all of the sites are nearly 100% methylated at day 1. By day 3, the upstream sites become ~50% methylated except the −53 CpG which was <20%. This pattern persisted at day 10. By day 14 the promoters had become largely remethylated. For cells treated with 5-Aza starting on day 10, there was no change in the levels of methylation seen on days 1,3 and 10, but at day 14 the low levels of upstream methylation persisted - just as γ-globin expression does. However, in both treated and untreated cells, down-stream CpG sites were highly methylated at all time points. This suggests that γ promoter demethylation may be due to a local and not a generalized effect of 5-Aza on cellular DNA methylation. We also made two unexpected observations. At a 300nM dose of 5-Aza, γ-globin mRNA is ~doubled while β-globin mRNA levels are ~halved - indicating that 5-Aza not only induces γ-globin expression also suppresses β-globin. Also despite only a doubling in γ-globin mRNA, there was an ~50-fold increase in HbF, from ~1% to more than 50%, while total per cell Hb levels were unchanged. Neither of these results are easily explained by current models of γ-globin gene induction. Our results raise the possibility that mechanisms beyond cytotoxicity and generalized DNA demethylation may be responsible for pharmacologic induction of γ-globin mRNA and HbF.

Differences in Fetal Hemoglobin Induction in Sickle Cell Disease and beta-Thalassemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 555-555 ◽  
Author(s):  
Hassana Fathallah ◽  
Ali Taher ◽  
Ali Bazarbachi ◽  
George F. Atweh
Keyword(s):  
Gene Expression ◽  
Sickle Cell Disease ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Mrna Levels ◽  
Globin Genes ◽  
Thalassemia Intermedia ◽  
Cell Disease ◽  
Globin Mrna ◽  
Globin Gene Expression

Abstract A number of therapeutic agents including hydroxyurea, butyrate and decitabine have shown considerable promise in the treatment of sickle cell disease (SCD). However, the same agents have shown less clinical activity in β-thalassemia. As a first step towards understanding the molecular basis of the different clinical responses to these agents, we have studied the mechanisms of induction of fetal hemoglobin (HbF) by butyrate in BFU-E derived cells from 5 patients with SCD and 9 patients with β-thalassemia intermedia. Exposure to butyrate resulted in a dose-dependent augmentation of γ-globin mRNA levels in erythroid cells from patients with SCD. In contrast, induction of γ-globin expression in erythroid cells from patients with β-thalassemia intermedia was only seen at a high concentration of butyrate. The increase in γ-globin mRNA levels in patients with SCD and β-thalassemia intermedia was associated with opening of the DNA structure as manifested by decreased DNA methylation at the γ-globin promoters. Interestingly, butyrate exposure had markedly different effects on the expression of the β- and α-globin genes in the two categories of patients. Butyrate decreased the level of β-globin mRNA in 4 out of 5 patients with SCD (P = 0.04), while in β-thalassemia the levels of β-globin mRNA did not change in 7 patients and decreased in 2 patients after butyrate exposure (P = 0.12). Thus in patients with SCD, the effects of the induction of the γ-globin gene on the γ/(β+γ) mRNA ratios were further enhanced by the butyrate-mediated decreased expression of the β-globin gene. As a result, γ/(β+γ) mRNA ratios increased in all patients with SCD, with a mean increase of 31% (P = 0.002). In contrast, butyrate increased γ/(β+γ) mRNA ratios only in 4 out of 9 patients with β-thalassemia, with a more modest mean increase of 12% (P = 0.004). Interestingly, the decreased β-globin expression in patients with SCD was associated with closing of the DNA configuration as manifested by hypermethylation of DNA at the promoter of the β-globin gene while methylation of the same promoter did not change following butyrate exposure in patients with β-thalassemia intermedia. More surprisingly, the expression of the α-globin genes increased following butyrate exposure in 4 out of 9 patients with β-thalassemia, while the levels of α-globin mRNA decreased in 4 out of 5 patients with SCD. As a result, the favorable effects of the butyrate-induced increase in γ-globin gene expression on the α: non-α mRNA imbalance in patients with β-thalassemia intermedia were partly neutralized by the corresponding increase in α-globin gene expression. These differences may explain, at least in part, the more favorable effects of inducers of HbF in SCD than in β-thalassemia. Further studies are necessary to fully understand the molecular bases of the different responses to agents that induce HbF in patients with these disorders.

scholarly journals Antagonistic Regulation of β-Globin Gene Expression by Helix-Loop-Helix Proteins USF and TFII-I

2006 ◽  
Vol 26 (18) ◽  
pp. 6832-6843 ◽  
Author(s):  
Valerie J. Crusselle-Davis ◽  
Karen F. Vieira ◽  
Zhuo Zhou ◽  
Archana Anantharaman ◽  
Jörg Bungert
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Control Region ◽  
Adult Stage ◽  
Globin Gene ◽  
Locus Control Region ◽  
Erythroid Cell ◽  
Erythroid Cells ◽  
Globin Gene Expression ◽  
In Erythroid Cells

ABSTRACT The human β-globin genes are expressed in a developmental stage-specific manner in erythroid cells. Gene-proximal cis-regulatory DNA elements and interacting proteins restrict the expression of the genes to the embryonic, fetal, or adult stage of erythropoiesis. In addition, the relative order of the genes with respect to the locus control region contributes to the temporal regulation of the genes. We have previously shown that transcription factors TFII-I and USF interact with the β-globin promoter in erythroid cells. Herein we demonstrate that reducing the activity of USF decreased β-globin gene expression, while diminishing TFII-I activity increased β-globin gene expression in erythroid cell lines. Furthermore, a reduction of USF activity resulted in a significant decrease in acetylated H3, RNA polymerase II, and cofactor recruitment to the locus control region and to the adult β-globin gene. The data suggest that TFII-I and USF regulate chromatin structure accessibility and recruitment of transcription complexes in the β-globin gene locus and play important roles in restricting β-globin gene expression to the adult stage of erythropoiesis.

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