KLF1 acts both directly and indirectly, to affect HbF expression. to death of these precursors, causing ineffective production of erythroid cells. performed experiments, analyzed and interpreted data, and wrote the manuscript; and A.A., N.S., D.N., P.S., D.H.K.C., and M.H.S. enhancer of definitive erythropoiesis during mouse development, Progression through key stages of haemopoiesis is dependent on distinct threshold levels of c-Myb, Role of epigenetic modifications in normal globin gene regulation and butyrate-mediated induction of fetal hemoglobin, Regulation of embryonic/fetal globin genes by nuclear hormone receptors: A novel perspective on hemoglobin switching, Molecular cloning and characterization of the human β-like globin gene cluster, Amelioration of Sardinian β0 thalassemia by genetic modifiers, Fine-mapping at three loci known to affect fetal hemoglobin levels explains additional genetic variation, Ten novel mutations in the erythroid transcription factor KLF1 gene associated with increased fetal hemoglobin levels in adults, Chromatin structure of endogenous retroviral genes and activation by an inhibitor of DNA methylation, Genetic complexity in sickle cell disease, Allogeneic hematopoietic stem-cell transplantation for sickle cell disease, Developmental hemoglobin anomalies in a chromosomal triplication: D1 trisomy syndrome, Hemoglobin switching in man and chicken is mediated by a heteromeric complex between the ubiquitous transcription factor CP2 Although in the initial report, all recipients of the missense mutation had elevations in HbF expression, it should Evidence of genetic interaction between the beta-globin complex and chromosome 8q in the expression of fetal hemoglobin. This might be related to the premature destruction of erythrocytes that do not contain HbF, even though the total HbF concentration is high. 2011c). High fetal hemoglobin production in sickle cell anemia in the eastern province of Saudi Arabia is genetically determined. 12 cytokines, 176. The switching from hemoglobin F to hemoglobin A formation in man: parallels between the observations in vivo and the findings in erythroid cultures. However, studying the role of these factors in Absence of cross-resistance to the Hb F stimulating activities of butyrate and hydroxyurea. The Prevalence of Nonalcoholic Fatty Liver Disease and Its Risk Factors in Children and Young Adults with Type 1 Diabetes Mellitus Janejira Sae-wong, Bundit Chaopathomkul, Teerasak Phewplung, Nataruks Chaijitraruch, Taninee Sahakitrungruang approach by which such molecules can be therapeutically manipulated remains unclear. To examine genetic modifiers of HbF level in patients from the Southwestern Province, the 3 HbF QTLs were genotyped in 77 patients, 17.7 ± 10 years of age, 69% with sickle cell anemia and 31% with HbS-β0 thalassemia.73  The distribution of HBB gene cluster haplotypes was: 74% Benin, 22% Bantu, and 4% others. activity to reverse DNA methylation in a variety of mammalian cell types (Jones and Taylor 1980; Groudine et al. the role of BCL11A in the developmental process of globin switching in mice (Sankaran et al. secondarily to the HbF-inductive effect of BCL11A (or HDAC) inhibition. MicroRNA-15a and -16-1 act via MYB to elevate fetal hemoglobin expression in human trisomy 13. 2006). 1984; Platt 2008). Mortality in sickle cell disease. F-cell production in sickle cell anemia: regulation by genes linked to beta-hemoglobin locus. Suberoylanilide hydroxaminc acid (Vorinostat), an orally available agent approved for treatment of cutaneous T-cell lymphoma, is an HDAC inhibitor that induced HbF expression in K562 cells.89  A phase 1/2 trial of this agent in sickle cell anemia is presently enrolling patients (#NCT01000155). A model for regulation of γ-globin silencing in the human β-globin locus. was tested and showed a potent ability to induce the silenced γ-globin genes in adult erythroid cells of primates (DeSimone et al. mind that the additive genetic variation found from common genetic variants ignores potential higher-order genetic interactions There was great hope and promise that this would lead to a broadly applicable targeted molecular approach for HbF induction (Benz 1982), but there was significant concern over the mutagenic potential of 5-azacytidine. this molecule for HbF induction. A variety of β-like globin Clearly innovation will be necessary for translating the knowledge gained Sickle cell trait carriers or persons with HbA and the Saudi-Indian haplotype did not have high HbF, but the cultured erythroblasts of sickle cell trait patients with the Saudi-Indian haplotype made increased amounts of HbF, suggesting that the kinetics of erythropoiesis played a role in the expression of the high HbF determinant.39,75,76. Therefore, trials of hydroxyurea, an S-phase specific agent without primary hypomethylating activity, with a long history of use in myeloproliferative disorders and with tolerable side effects, were started. such as BCL11A or MYB could lead to synergistic effects. Disorders of Hemoglobin: Genetics, Pathophysiology, and Clinical Management (2nd ed). BCL11A for HbF induction. Trials An alternative and perhaps simpler approach, would involve targeting of enzymatic partner proteins of these transcription and better understand the mechanisms through which this complex may be acting to alter human globin gene regulation. to remove this region, as shown by the model below. 2004). when overexpressed in sickle cell disease mouse models can result in partial amelioration of hematologic and pathologic symptoms High HbF and Low HbF represent the major allele frequencies in the 2 groups. initially seen in the ability of this molecule to stimulate HbF production and reduce clinical markers of disease (Ley et al. path to effective therapies may not always be straightforward. For example, combining hydroxyurea with specific targeting of factors The 20 “high” HbF cases were 16.3 ± 8.3 years of age and had a hemoglobin level of 9.0 ± 1.3 g/dL, mean corpuscular volume 87.9 ± 9.0 fL, and HbF 17.2% ± 4.8%. BCL11A rs766432 and HMIP rs9399137 had a higher minor allele frequency in patients with “high” HbF in both datasets and accounted for 20% of HbF variance. This in turn results in deformation of molecules are produced as a result of the fact that the human β-globin locus on chromosome 11 is developmentally regulated The online version of this article contains a data supplement. 1994). A partial list of fetal hemoglobin regulators. The effect of prolonged administration of hydroxyurea on morbidity and mortality in adult patients with sickle-cell syndromes: results of a 17-year, single center trial (LaSHS). The bottom illustration also depicts the upstream enhancer of the β-globin locus, known as the locus control region (LCR), with its Not all patients respond to hydroxyurea, and the erythrocytic distribution of HbF in treated patients is heterocellular.86  Among responders, the increment in HbF is variable, suggesting the need for additional agents capable of inducing HbF and perhaps broadening its cellular distribution. The rarity of stroke might be a result of the higher hemoglobin concentration and a high incidence of α-thalassemia; little information on the incidence of pulmonary vasculopathy is available. hemoglobin for much of gestation. 2010; Satta et al. Polymorphisms were identified in the HBD-HBG1 intergenic region, and many lead to creation or abolition of transcription factor binding sites and some bind transcription factors presumed to have regulatory roles in globin gene expression when examined in silico. and switching was shown in mice (Sankaran et al. the expression of BCL11A using shRNAs (Borg et al. of this beneficial form of hemoglobin. HPFH-1 and HPFH-2 deletions span more than 80 kb and are the most common types of HPFH found in African Americans and Africans. In addition to the basic science necessary for these translational 2010). hemoglobin switch. This illustration depicts the human β-globin locus as shown in Figure 1 with an ∼3-kb region upstream of the δ-globin gene that was found by comparing the regions removed in various hereditary persistence of fetal hemoglobin (HPFH) deletions with the regions removed by δβ-thalassemia deletions (Sankaran et al. This is accompanied by a progressive decline in the number of erythrocytes with measurable HbF, called F cells. Splenic function in sickle cell anemia patients in Qatif, Saudi Arabia. HbF silencing (Bradner et al. Arginine butyrate, a short chain fatty acid with HDAC inhibitory activity used as single agent or with hydroxyurea, has been associated with increases in HbF.87,88  However, a pulsed, or intermittent, dosing regimen was necessary to avoid cytotoxicity from butyrate while retaining the targeted promoter activation. Paradoxically, overexpression of TR2 and TR4 in transgenic mouse models results in elevated expression of γ-globin and in the fetal liver (McGrath and Palis 2008), the predominant β-like globin molecule produced is γ-globin (Sankaran et al. effective approaches for HbF induction. A second group examined the genetic basis of an unlinked form of HPFH that was suggested to result from a KLF1 missense mutation in this family (Borg et al. This molecule is encoded by two duplicated γ-globin genes found within the β-globin gene cluster (Fig. regulators of globin and erythroid gene regulation. in mortality from infectious and nutritional causes—there will likely be an increase in the prevalence of these diseases in Five Saudi families from the Eastern Province, which included 7 patients with sickle cell anemia who had a median HbF of 30.3% (range, 18%-41%), were studied (A.A., personal communication, March 2011). 50 Likes, 2 Comments - College of Medicine & Science (@mayocliniccollege) on Instagram: “ Our Ph.D. HbS-Hb Kenya compound heterozygotes had mild microcytic anemia and an average of 10% HbF in a pancellular distribution. The only potentially curative therapies that are available for these diseases are bone marrow transplantation (Michlitsch and Walters 2008) and gene therapy (Persons 2009), but there are numerous challenges that exist to implement these treatments and they have significant limitations for widespread BERNARD G. FORGET, in Proceedings of the 1981 Laurentian Hormone Conference, 1982 D HEREDITARY PERSISTENCE OF FETAL HEMOGLOBIN (HPFH). A database of reported HPFH mutations is available (www.globin.bx.psu.edu/hbvar/menu.html). 2011; Zuber et al. Therefore, developing improved therapies for these disorders will be of paramount importance for this important show a similar connection using shRNA approaches. Sickle cell leg ulcers: associations with haemolysis and SNPs in Klotho, TEK and genes of the TGF-beta/BMP pathway. DNA sequence variation in a negative control region 5′ to the beta-globin gene correlates with the phenotypic expression of the beta s mutation. was in part attributable to a silencing effect of KLF1 on BCL11A. BCL11A binding sites are present between coordinates 44000, 45000, 53000, and 54000. The hydroxyurea-induced small GTP-binding protein SAR modulates gamma-globin gene expression in human erythroid cells. None of these factors appeared to be specific regulators of the fetal-to-adult This led to small clinical trials with the safest of these compounds, hydroxyurea, in SCD patients in which HbF-inductive 15a and 16-1 (Sankaran et al. 2008). 2005). T to C substitution at -175 or -173 of the gamma-globin promoter affects GATA-1 and Oct-1 binding in vitro differently but can independently reproduce the hereditary persistence of fetal hemoglobin phenotype in transgenic mice. use, particularly in the developing world (Sankaran and Nathan 2010b). in erythroid cells, The significance of the paucity of sickle cells in newborn Negro infants, Phenotype-genotype relationships in monogenic disease: Lessons from the thalassaemias, Disease control priorities in developing countries, Therapeutic levels of fetal hemoglobin in erythroid progeny of β-thalassemic CD34, Transcriptional silencing of γ-globin by BCL11A involves long-range interactions and cooperation with SOX6, Correction of sickle cell disease in adult mice by interference with fetal hemoglobin silencing, Repression of human γ-globin gene expression by a short isoform of the NF-E4 protein is associated with loss of NF-E2 and Investigators of the Multicenter Study of production, which may not always be relevant in humans in vivo. erythroid specific transcription factor KLF1 using independent and complimentary approaches. 1994; Sankaran et al. In addition, rs10128556 had an effect on HbF independent of rs7482144 (P = .047), and rs7482144 had no effect on HbF independent of rs10128556 (P = .78).36  However, this determination was based on conditional haplotype tests that excluded uninformative haplotypes. Although ACS can occur in any SCD phenotype, including HbS-hereditary persistence of fetal hemoglobin, individuals with HbSS have the highest rate of ACS . 2011), suggesting that such strategies could potentially also be effective in humans. ; and RC2 HL101211, M.H.S.). BCL11A has been shown to bind to chromatin within this 3-kb region, along 2010). However, further mechanistic studies of these HbF regulators will be needed before such strategies can be successfully Fetal haemoglobin response to hydroxycarbamide treatment and sar1a promoter polymorphisms in sickle cell anaemia. At least 8 HPFH-causing deletions within the HBB gene-like cluster of 10 to more than 80 kb have been described. In the course of this work, it was noted that the γ-globin genes underwent DNA methylation when silenced in adult erythroid progenitors, while not having DNA methylation present when In one study, a mouse with a With the epidemiological transition that most developing countries are currently undergoing—with significant decreases as shown in Figure 1 with an ∼3-kb region upstream of the δ-globin gene that was found by comparing the regions removed in various hereditary persistence of fetal hemoglobin (HPFH) deletions In the decades following the molecular cloning of the globin genes, a variety of transcription factors that played roles in A number of small molecule inhibitors of these molecules exist (Bradner et al. A similar phenomenon occurs when cells are treated with HDAC inhibitors that induce γ-globin gene expression (Bradner et al. In a recent examination of 28 cases of HbS-HPFH (6 HPFH-1 and 22 HPFH-2), the hemoglobin concentration was 13 ± 1 g/dL, mean corpuscular volume 75 ± 6 fL, and HbF 31% ± 2% (D.N., personal communication, March 2011). 2011c). these and other molecules that regulate this process will lead to mechanistically based approaches for HbF induction. 1972; Kar et al. erythroid progenitors and γ-globin expression could be robustly induced on such a knockdown. Effects of 5-aza-2′-deoxycytidine on fetal hemoglobin levels, red cell adhesion, and hematopoietic differentiation in patients with sickle cell disease. Engineering recombinant HbF and HbA by adding additional substitutions can enhance the capacity of the molecule to inhibit polymerization, an approach exploited when devising vectors for gene therapy. Hemoglobin F (fetal hemoglobin). 54 Likes, 13 Comments - Residents (@lapmrresidency) on Instagram: “Resident’s Corner: Name: David Huy Blumeyer, MD Year in residency: PGY-4 Where were you born…” switch holds great promise for allowing more effective and specifically targeted approaches for HbF induction to be developed. The majority of molecules that have been identified as regulators of the fetal-to-adult hemoglobin switch and HbF silencing an S-phase inhibitor, may play a role in this activity. (Bard and Prosmanne 1985; Perrine et al. HbF levels are higher in Saudi-Indian haplotype patients when they are compared with African Americans homozygous for the Senegal haplotype whose mean HbF was 12.5% ± 5.3%, even though both haplotypes share the 5′ HBG2 C-T polymorphism (rs7482144). Children with type 1 diabetes typically present with the hallmark symptoms of polyuria/polydipsia, and approximately one-third present with diabetic ketoacidosis (DKA) ( 2 ). target KLF1 for HbF induction, particularly if the untoward effects of such inhibition on erythroid differentiation are to therapeutic approaches for HbF induction. Three of the SNPs were between positions 49213 and 49994, and one was at position 54541. appeared to be related to the extent of knockdown of BCL11A. In one of the singular successes of GWASs, BCL11A polymorphisms were strongly associated with HbF concentrations in normal persons and several different populations of patients with β-thalassemia and with sickle cell anemia. BCL11A was the sole QTL associated with HbF level, but the study was underpowered to detect associations with small effect sizes and with SNPs having a low minor allele frequency similar to those in HMIP and HBB. Characterization of two types of fetal hemoglobin: alpha2 G gamma2 and alpha2 Agamma2. Natural history of sickle cell anemia in Saudi Arabs: a study of 270 subjects. 2010) suggests that targeting both of these pathways together could yield even more robust effects than targeting either pathway Deconstructing sickle cell disease: reappraisal of the role of hemolysis in the development of clinical subphenotypes. 2011a). 2010). 2011). 1982). 2007; Lettre et al. with the regions removed by δβ-thalassemia deletions (Sankaran et al. Although this initial study addressed Hemoglobin S in moderate amounts can mean that sickle cell trait is present. 2009; Cavazzana-Calvo et al. These studies resulted in the identification of three genomic loci harboring common variants that influenced HbF levels. Although the trial's primary endpoints of preservation of renal and splenic function were not met during the relatively brief observation period, treated patients had less pain, higher hemoglobin concentrations, increased HbF, and reduced leukocyte counts, with minimal short-term toxicity.85  The long-term effects of hydroxyurea begun in the neonatal period will require careful follow-up. It has been suggested that these short-chain fatty acids 2011c). This notion was substantiated by observations of rare patients with compound heterozygosity for sickle cell disease and