Butyrate Downregulates the Expression of a Number of Repressors of Fetal Hemoglobin In Definitive Erythroid Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2080-2080 ◽  
Author(s):  
Radha Raghupathy ◽  
Shay Karkashon ◽  
Melissa J Fazzari ◽  
Jane A Little
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Short Chain Fatty Acids ◽  
Short Chain ◽  
Beta Globin ◽  
Erythroid Cells ◽  
Rt Pcr ◽  
Globin Gene Expression

Abstract Abstract 2080 Elevated fetal hemoglobin (HbF) is ameliorative for beta-globin gene disorders. Butyrate, a short chain fatty acid, is a potent inducer of fetal hemoglobin with limited clinical applicability. We wanted to examine non-globin gene targets of butyrate that are regulated in definitive erythroid cells prior to the induction of embryonic/fetal beta-type globin genes. Mechanistic insights may improve clinical utility for short chain fatty acids by identifying novel molecular therapeutic targets. Induced embryonic/fetal globin gene expression is detectable in murine fetal liver-derived definitive erythroid cells (FL EryD) from wildtype and human beta-globin YAC transgenic mice after 19 hours in culture with butyrate & erythropoietin (EPO), but not in EPO alone. Differential regulation of non-globin gene targets in wildtype FL EryD was studied on a Mouse Gene 1.0ST Affymetrix Array after culture in EPO only or butyrate & EPO at 6 hours (when no embryonic globin gene expression is detectable, n=3). Data from biological replicates were normalized by robust multichip average and analyzed with expression console software. As shown in Table 1, several confirmed and putative repressors of embryonic/fetal beta-type globin gene expression, including SOX6, Bcl11A, and Ikaros 1 (but not cMyb) were significantly down regulated by Butyrate at 6 hours (n=3); this was confirmed by RT-PCR. The histone deacetylase inhibitor trichostatin A (TSA), which also induces embryonic globin gene expression in murine FL EryD, has a directionally similar effect (Table 1). Down regulation of some fetal/embryonic globin gene repressors, relative to identically handled EPO-only treated samples, was detectable by RT-PCR as early as 60 to 120 minutes after butyrate induction. These repressors included Bcl11A (60min: 0.66±0.005, p<.001, n=2; 120min: 0.4±0.24, p<.01, n=4), Sox6 (60min: 0.55± 0.18, p=0.08, n=2; 120min: 0.63± 0.06, p<.001, n=4) and Ikaros1 (60min: 0.63±0.45, p=0.36, n=2; 120min: 0.42±0.15, p<.001, n=4). The proximate molecular mechanisms through which butyrate act, while unknown in detail, have been posited to include ‘stress’ signaling via p38 and/or direct activation of gamma-globin gene expression through inhibited histone deacetylation. We found no evidence for butyrate-mediated enhancement of p38 phosphorylation in FL EryD at 0–120 minutes in culture. However, bulk histone acetylation measured by western for histone 3 (H3), was >1.5 fold greater with butyrate induction at 60–90 minutes relative to baseline, while less than baseline in EPO-only treated FL EryD (n=2). Cumulatively, these data suggest that the down regulation by butyrate of major molecular repressors of embryonic/fetal globin gene expression, likely mediated directly or indirectly through epigenetic modifications, is a key underlying mechanism for the induction of fetal hemoglobin in definitive erythroid cells by short chain fatty acids. Disclosures: No relevant conflicts of interest to declare.

Enhanced Erythroid Differentiation of Murine Embryoid Bodies That Are Exposed to Short-Chain Fatty Acids during Development.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3646-3646
Author(s):  
Jennifer L. Hallock ◽  
Lauren J. Sterner ◽  
Jane A. Little
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Cell Surface ◽  
Es Cells ◽  
Globin Gene ◽  
Short Chain Fatty Acids ◽  
Embryoid Bodies ◽  
Short Chain ◽  
Globin Genes ◽  
Globin Gene Expression

Abstract Embryonic/fetal-type globin genes are known to be up-regulated in models of adult erythropoiesis following exposure to short-chain fatty acids (SCFAs, butyrate or propionate), in a subset of beta-globin gene disorder patients treated with SCFAs, and in children with metabolic disorders that result in high levels of endogenous SCFAs. Here, we investigate a role for SCFAs during development, using a murine embryonic stem (ES) cell model. Globin gene expression and cell-surface marker presentation were examined in murine embryoid bodies (EBs), which differentiate from ES cells and which recapitulate many features of early murine development. ES cells were allowed to differentiate (through the removal of both LIF and contact inhibition, without cytokines), in the absence or presence of SCFAs. Expression of alpha- and beta-type globin gene RNA and transcription factor RNA in the developing EBs was analyzed daily or every-other-day for 10–14 days by real-time PCR with gene-specific primers and probes. At day +2 and +6 /7 EBs were disaggregated, labeled, and analyzed by fluorescent-activated cell sorting (FACS) with labeled antibodies that had been raised against cell-surface markers of hematopoietic and endothelial differentiation. Globin gene expression was augmented by SCFAs in all experiments, with maximal induction, when compared with untreated cells, at approximately day + 7 of differentiation; Comparative globin gene expression, between propionate-exposed and untreated, in 3 separate EB experiments and normalized to 18S expression, was variable, but was elevated for all globin genes examined, as shown in Table I. Absolute RNA expression, normalized to 18S in a representative experiment testing butyrate or propionate as inducers, indicated that alpha, zeta, and beta H1/0 were effected most by SCFAs, (in which expression ranged between 30- and 40-fold relative to 18S) while Beta major and Epsilon-y (ranging between 1- and 7-fold relative to 18S) were effected to a much lesser extent; This trend, in which alpha, zeta, and Beta H1/0 induction by SCFAs was more dramatic than that seen for Epsilon-y and beta major induction, was noted in all experiments. In a single analysis, RNA for BMP-4 and GATA-2 was up-regulated on D + 7 by SCFAs at, respectively, 7- and 18- fold, which was not true for other hematopoietic transcription factors examined, such as LMO-2, GATA-1, EKLF-1, or AML-1, FACS analyses of untreated vs. SCFA-treated EBs in three separate experiments were analyzed with a screening gate for hematopoietic cells (CKit). These experiments showed a modest increase in the hematopoietic marker CD34 in SCFA-treated vs. un-treated cells; a doubling in CKit-positive calls that expressed late erythroid markers on Day + 6, from 5.6 +/− 2% to 12.1 +/− 6.0 % TER-119 positive (P&lt;.05), and a 3-fold, but variable increase, from 1.4 +/− 1.5 % to 4.2 +/− 4.1 % EPO-Receptor positive (n.s.). Expression of CD 45, CD 41, PECAM, and FLK-1 was not consistently different between EBs differentiated in the absence or presence of SCFAs. These data suggest that SCFAs minimally enhance hematopoiesis, but markedly enhance erythropoiesis, during differentiation in a murine developmental model; we speculate that SCFAs and related compounds could play a similar role in vivo during development. Range of globin gene expression, SCFA- vs. un-treated EBs Globin Genes Fold-expression Alpha 5- to 22-fold Zeta 4.2- to 35-fold Beta H1/0 5- to 22.5-fold Epsilon-y 9-to 96-fold Beta Major 2.5- to 22-fold

Short Chain Fatty Acids and p38 in the Induction of Embryonic/Fetal Globin Genes During Definitive Erythropoiesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 460-460
Author(s):  
Amrita Dutta ◽  
Himanshu Bhatia ◽  
Shay Karkashon ◽  
Lydia Tesfa ◽  
Jane Little
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Cell Division ◽  
Globin Gene ◽  
Short Chain Fatty Acids ◽  
Primary Cell ◽  
Short Chain ◽  
Cell Divisions ◽  
Definitive Erythropoiesis ◽  
Globin Gene Expression

Abstract Abstract 460 Augmentation of fetal hemoglogin (HbF) is therapeutically desirable in β –globin gene disorders, such as sickle cell anemia and β-thalassemia. Short chain fatty acids (SCFAs) can augment embryonic/fetal β-type globin gene expression in vivo and in vitro during adult definitive erythropoiesis (EryD), but the underlying molecular mechanisms are not well understood. p38 signaling, triggered by stress erythropoiesis, has been implicated in the induction of fetal globin gene expression. Here, we examined p38 signaling and its effects using a murine primary cell model of EryD, isolated from fetal liver. This model overcomes some limitations of previously used transformed or long-term primary cell models, and has afforded complementary data. E14.5 erythroid fetal cells (eFLCs) were examined at harvest and after culture in insulin and erythropoietin (‘ins/EPO') with or without the SCFA butyrate, and in the presence or absence of p38 inhibitors SB 203580, SB 202190, PD 169316 at concentrations of 0-50 μM for up to 72 hours. Western blots showed that p38 phosphorylation was constitutive at harvest and preserved in cultures with ins/EPO, but was diminished by half after concurrent culture in PD169316. Embryonic globin gene expression, ((βH1+εY)/(βH1+εY+βMAJ) × 100), was analyzed by real-time PCR, normalized to 18S expression. Embryonic globin gene induction, relative to maximal expression at 72 hours in butyrate with ins/EPO, was blocked in a dose dependent manner by all inhibitors of p38 signaling, at 10-30% of maximal induction when cultured in 50 mM of any inhibitor. Primary transcripts from the adult β-globin gene, βmaj, were likewise diminished by p38 inhibition, with a median level of 8.3% and 4.0% of maximal transcript in ins/EPO and butyrate & ins/EPO respectively after culture for 72 hours in 50 μM PD 169316 (n=3, p<.01 relative to non-inhibited cultures). Erythroid differentiation, analyzed by FACS quantitation of CD71 and TER119 co-immunostaining, was delayed by p38 inhibitors, with 22-38% of ins/EPO +/- SCFA-treated cells comprised of orthochromatophilic cells after 72 hours, compared with 4-8% of parallely treated cells to which p38 inhibitors had been added. To further explore stress erythropoesis, cell divisions were analyzed using carboxyfluorescein succinimidyl ester (a fluorescent cytoplasmic dye that is diluted with each cell division) as monitored by FACS. Cell divisions were modestly slowed, but not blocked, by SCFAs. A median of 60% of ins/EPO-, vs. 29% of butyrate & ins/EPO-, treated cells had undergone 2 cell divisions at 48 hours (n=2, p<.05), but by 72 hours a median of 56% and 51% of treated cells, respectively, had completed 2 divisions (n=2, p=n.s.). In contrast, cell division was perturbed by p38 inhibitors, with <26% of eFLCs having undergone a 2nd division by 72 hours. Our studies suggest that p38 signaling is required for, but is not specific to, the SCFA-mediated induction of embryonic/fetal globin gene expression. We do not find that p38 phosphorylation is stimulated by SCFAs in short-term primary EryD. The central role that p38 signaling plays in the induction of embryonic and fetal globin gene expression, as manifested by lost induction with p38 inhibition, may instead reflect p38's constitutive function in cell division and differentiation. Disclosures: No relevant conflicts of interest to declare.

Hydroxamide derivatives of short-chain fatty acids are potent inducers of human fetal globin gene expression

2003 ◽  
Vol 31 (3) ◽  
pp. 197-203 ◽  
Author(s):  
Evangelia Skarpidi ◽  
Hua Cao ◽  
Birgit Heltweg ◽  
Brian F White ◽  
Ronald L Marhenke ◽  
...  
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Globin Gene ◽  
Short Chain Fatty Acids ◽  
Short Chain ◽  
Derivatives Of ◽  
Globin Gene Expression ◽  
Chain Fatty Acids

scholarly journals 5'-flanking sequences mediate butyrate stimulation of embryonic globin gene expression in adult erythroid cells.

1991 ◽  
Vol 11 (9) ◽  
pp. 4690-4697 ◽  
Author(s):  
J G Glauber ◽  
N J Wandersee ◽  
J A Little ◽  
G D Ginder
Keyword(s):  
Gene Expression ◽  
Cell Differentiation ◽  
Globin Gene ◽  
Beta Globin ◽  
Erythroid Cells ◽  
Adult Chicken ◽  
Beta Globin Gene ◽  
Flanking Sequences ◽  
Murine Erythroleukemia ◽  
Globin Gene Expression

A stable transfection assay was used to test the mechanism by which embryonic globin gene transcription is stimulated in adult erythroid cells exposed to butyric acid and its analogs. To test the appropriate expression and inducibility of chicken globin genes in murine erythroleukemia (MEL) cells, an adult chicken beta-globin gene construct was stably transfected. The chicken beta-globin gene was found to be coregulated with the endogenous adult mouse alpha-globin gene following induction of erythroid differentiation of the transfected MEL cells by incubation with either 2% dimethyl sulfoxide (DMSO) or 1 mM sodium butyrate (NaB). In contrast, a stably transfected embryonic chicken beta-type globin gene, rho, was downregulated during DMSO-induced MEL cell differentiation. However, incubation with NaB, which induces MEL cell differentiation, or alpha-amino butyrate, which does not induce differentiation of MEL cells, resulted in markedly increased levels of transcription from the stably transfected rho gene. Analysis of histone modification showed that induction of rho gene expression was not correlated with increased bulk histone acetylation. A region of 5'-flanking sequence extending from -569 to -725 bp upstream of the rho gene cap site was found to be required for both downregulation of rho gene expression during DMSO-induced differentiation and upregulation by treatment with NaB or alpha-amino butyrate. These data are support for a novel mechanism by which butyrate compounds can alter cellular gene expression through specific DNA sequences. The results reported here are also evidence that 5'-flanking sequences are involved in the suppression of embryonic globin gene expression in terminally differentiated adult erythroid cells.

scholarly journals Stimulation of fetal hemoglobin production by short chain fatty acids

Blood ◽  
1995 ◽  
Vol 86 (8) ◽  
pp. 3227-3235 ◽  
Author(s):  
E Liakopoulou ◽  
CA Blau ◽  
Q Li ◽  
B Josephson ◽  
JA Wolf ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Short Chain Fatty Acids ◽  
Short Chain ◽  
Erythroid Cell ◽  
Gamma Globin ◽  
Carbon Fatty Acid ◽  
Chain Fatty Acids

Abstract Butyrate, a four-carbon fatty acid, and its two-carbon metabolic product, acetate, are inducers of gamma-globin synthesis. To test whether other short-chain fatty acids share this property, we first examined whether propionic acid, a three-carbon fatty acid that is not catabolized to acetate, induces gamma-globin expression. Sodium propionate increased the frequency of fetal hemoglobin containing erythroblasts and the gamma/gamma + beta mRNA ratios in adult erythroid cell cultures and F reticulocyte production in a nonanemic juvenile baboon. Short-chain fatty acids containing five (pentanoic), six (hexanoic), seven (heptanoic), eight (octanoic), and nine (nonanoic) carbons induced gamma-globin expression (as measured by increase in gamma-positive erythroblasts and gamma/gamma + beta mRNA ratios) in adult erythroid burst-forming unit cultures. There was a clear-cut relationship between the concentration of fatty acids in culture and the degree of induction of gamma-globin expression. Three-, four-, and five-carbon fatty acids were better inducers of gamma globin in culture as compared with six- to nine-carbon fatty acids. These results suggest that all short-chain fatty acids share the property of gamma-globin gene inducibility. The fact that valproic acid, a derivative of pentanoic acid, also induces gamma-globin expression suggests that short-chain fatty acid derivatives that are already approved for human use may possess the property of gamma-globin inducibility and may be of therapeutic relevance to the beta-chain hemoglobinopathies.

scholarly journals EHMT1 and EHMT2 inhibition induces fetal hemoglobin expression

Blood ◽  
2015 ◽  
Vol 126 (16) ◽  
pp. 1930-1939 ◽  
Author(s):  
Aline Renneville ◽  
Peter Van Galen ◽  
Matthew C. Canver ◽  
Marie McConkey ◽  
John M. Krill-Burger ◽  
...  
Keyword(s):  
Gene Expression ◽  
Gene Locus ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Erythroid Cells ◽  
Adult Human ◽  
Key Points ◽  
Globin Gene Expression

Key Points EHMT1/2 inhibition increases human γ-globin and HbF expression, as well as mouse embryonic β-globin gene expression. EHMT1/2 inhibition decreases H3K9Me2 and increases H3K9Ac at the γ-globin gene locus in adult human erythroid cells.

Endogenous Elevations of Short Chain Fatty Acids Up-Regulate Embryonic Globin Gene Expression during Primitive Erythropoiesis.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1210-1210
Author(s):  
Lauren Sterner ◽  
Toru Miyazaki ◽  
Larry Swift ◽  
Ann Dean ◽  
Jane Little
Keyword(s):  
Gene Expression ◽  
Fatty Acids ◽  
Fetal Liver ◽  
Globin Gene ◽  
Short Chain Fatty Acids ◽  
Yolk Sac ◽  
Globin Genes ◽  
Wild Type ◽  
Alpha Type ◽  
Globin Gene Expression

Abstract We examined the effects of short chain fatty acids (SCFAs) on globin gene expression during development. We studied globin gene expression in transgenic mice that have endogenous elevations in the SCFA propionate due to a knockout (KO) of the gene for propionyl CoA carboxylase subunit A (PCCA, Miyazaki et al. JBC, 2001 Sep 21;276(38):35995–9). Serum propionate levels measured by gas chromatography were 2.5 to 3.6 mgms/ml in 2 adult PCCA KO mice and were undetectable in 2 wild type (wt) or heterozygous control adult mice. Embryonic PCCA KO offspring had propionate levels of 2.3 and 5.0 μgms/100 mgms of fetal liver, at day 16.5 (E16.5), while wt or heterozygotes at E14.5 had levels &lt;1 μgm/100 mgms. Analysis of expression from alpha (α), beta major (βmaj), embryonic beta-type epsilon-y (εy), embryonic beta-type beta H1 (βH1) and embryonic alpha-type zeta (ζ) globin genes plus 18S ribosomal RNA as a control was undertaken using real-time PCR with gene-specific primers and taqman probes. cDNA was reverse-transcribed from the mRNA of yolk sac (YS) and fetal liver of PCCA KO and wt progeny of more than one litter from timed pregnancies. Individual PCCA embryos at E10 (n=10), E12 (n=9), and E14 (n=7) were analyzed for globin gene expression, normalized to18S expression and were compared to age-matched wt embryos (n&gt;=4 for each time point). As expected, embryonic alpha- and beta-type globin gene expression (ζ and βH1 plus εy) predominated in E 10 YS, and definitive globin gene expression, α and βmaj, predominated in E12 or E14 fetal liver. Expression from embryonic alpha-type globin was calculated as normalized ζ/(ζ+α) and from embryonic beta-type globins as normalized (βH1+εy)/(βH1+εy+βmaj), see table. Embryonic globin gene expression was statistically significantly increased in PCCA KO E12 YS at 1.3 fold relative to wt ζ and in PCCA KO E14 YS at 1.8 fold and 2.1 fold relative to wt ζ or βH1 and εy respectively (p&lt;.05). No increase in embryonic globin mRNA was seen in adult PCCA KO animals. We conclude that elevations of SCFAs during normal murine development causes a persistence of both embryonic alpha-type and embryonic beta-type globin gene expression during primitive, but not definitive, erythropoiesis, suggesting that SCFAs cannot reactivate silenced murine embryonic globin genes in the absence of erythroid stress. Embryonic Globin Gene Expression in Mice with Endogenous Elevations of SCFAs % Expression PCCA KO wild type p value, t test E10 ζ Yolk Sac 53+/− 2 nd E10 βH1 & ε y Yolk Sac 99 +/− 0.3 nd E12 ζ Yolk Sac 32 +/− 3 25 +/− 1 p &lt; .05 E12 βH1 & ε y Yolk Sac 77 +/− 6 74 +/− 3 ns E14 ζ Yolk Sac 7 +/− 1.5 4 +/− 1.4 p &lt; .05 E14 βH1 & ε y Yolk Sac 13 +/− 6 6 +/− 0.5 p &lt; .05 E12 ζ Fetal Liver 11 +/− 4 9 +/− 2 ns E12 βH1 & ε y Fetal Liver 13 +/− 5 13+/− 3 ns E14 ζ Fetal Liver 1 +/− 0.4 0.7 +/− 0.2 ns E14 βH1 & εy Fetal Liver 6 +/− 1.8 4 +/− 1 ns

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

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 487-487 ◽  
Author(s):  
Vijay G Sankaran ◽  
Tobias F. Menne ◽  
Thomas E. Akie ◽  
Guillaume Lettre ◽  
Joel N. Hirschhorn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Developmental Stage ◽  
Disease Severity ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Erythroid Cell ◽  
Integrative Approach ◽  
Erythroid Cells ◽  
Nucleosome Remodeling ◽  
Globin Gene Expression

Abstract Numerous molecular approaches have been taken to elucidate the regulation of the human β-like globin genes, and particularly the “fetal” (γ- to β-) globin switch, given the role of fetal hemoglobin (HbF) levels on disease severity in the β-hemoglobin disorders. Despite these efforts, no developmental stage-specific nuclear regulators of HbF expression have been identified and validated. Recent genome-wide single nucleotide polymorphism (SNP) association studies by us and others have revealed novel loci that are significantly associated with HbF levels in normal, sickle cell, and thalassemia populations. One variant, lying within intron 2 of the chromosome 2 gene BCL11A, accounts for &gt;10% of the variation in HbF levels. We have now tested the hypothesis that BCL11A, a zinc-finger transcription factor, serves as a stage-specific regulator of HbF expression, rather than merely a genetic marker of HbF status. We found that BCL11A is expressed as two major isoforms (termed XL and L) in human erythroid progenitors. The level of BCL11A expression is inversely correlated with the expression of the HbF gene, γ-globin, in human erythroid cell types representative of different developmental stages. Expression of BCL11A is negligible in embryonic, and high in adult, erythroid cells. Correlation of SNP genotypes with levels of BCL11A RNA in cells derived from individuals of known genotypes indicates that the “high HbF” genotype is associated with reduced BCL11A expression. To better characterize its potential role in erythropoiesis and globin gene regulation, we identified interacting protein partners of BCL11A in erythroid cells through affinity purification and protein microsequencing. We found that the BCL11A protein exists in complexes with the nucleosome remodeling and histone deacetylase (NuRD) corepressor complex, as well as the erythroid transcription factors GATA-1 and FOG-1. Taken together, the genetic, developmental, and biochemical data are most consistent with a model in which BCL11A functions as a repressor of γ-globin gene expression. To directly test this possibility, we modulated expression of BCL11A in primary human erythroid precursors expanded from adult CD34+ progenitors. Transient or persistent knockdown of BCL11A accomplished by siRNA or lentiviral shRNA delivery, respectively, led to robust induction of γ-globin gene expression. Importantly, down-regulation of BCL11A expression did not alter the differentiation state or global transcriptional profile of the cells, suggesting an effect on a limited number of targets, including the γ-globin gene. In summary, these studies establish BCL11A as a potent regulator of human globin switching. As an adult-stage repressor, BCL11A represents a primary target for therapy aimed at reactivating HbF expression in patients with β-hemoglobin disorders. Our studies illustrate the power of an integrative approach to reveal the functional connection between a common genetic variant and a trait that serves as a prominent modifier of disease severity.

scholarly journals Fetal hemoglobin in sickle cell anemia: relation to regulatory sequences cis to the beta-globin gene. Multicenter Study of Hydroxyurea

Blood ◽  
1996 ◽  
Vol 87 (4) ◽  
pp. 1604-1611 ◽  
Author(s):  
ZH Lu ◽  
MH Steinberg
Keyword(s):  
Gene Expression ◽  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Globin Gene ◽  
Fetal Hemoglobin ◽  
Regulatory Sequences ◽  
Beta Globin ◽  
Beta Globin Gene ◽  
Gamma Globin ◽  
Globin Gene Expression

Very different fetal hemoglobin levels among adult sickle cell anemia patients suggest genetic modulation of gamma-globin gene expression. In sickle cell anemia, different fetal hemoglobin levels are associated with distinct beta-globin gene haplotypes. Haplotype may be a marker for linked DNA that modulates gamma-globin gene expression. From 295 individuals with sickle cell anemia, we chose for detailed studies 53 patients who had the highest or the lowest fetal hemoglobin levels and 7 patients whose fetal hemoglobin levels were atypical of their haplotype. In these individuals, we examined portions of the beta- globin gene locus control region hypersensitive sites two and three, an (AT)x(T)y repeat 5′ to the beta-globin gene, a 4-bp deletion 5 to the A gamma T gene, promoters of both gamma-globin genes, 5′ flanking region of the G gamma-globin gene, and A gamma-globin gene IVS-II. Of the regions we studied all polymorphisms were always haplotype-linked and no additional mutations were present. This suggested that variations in these areas are uncommon mechanisms of fetal hemoglobin modulation in sickle cell anemia. Whereas unexamined cis-acting sequences may regulate gamma-globin gene transcription, trans-acting factors may play a more important role.

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