Molecular analysis of the high-hemoglobin-F phenotype in Saudi Arabian sickle cell anemia

The relation between mitogen activated protein kinase (MAPK) pathway and different genes expression in patients with beta Thalassemia

BACKGROUND

β-thalassemia is an inherited hemoglobinopathy resulting in quantitative changes in the β-globin chain. Understanding the molecular basis of that disorder requires studying the expression of genes controlling the pathways that affect the erythropoietic homeostasis especially the MAPK pathway. The MAPKs are a family of serine/threonine kinases that play an essential role in connecting cell-surface receptors to DNA in the nucleus of the cell.

AIM

to study the effect of expression of GNAI2, DUSP5 and ARRB1 genes on MAPK signaling pathway in pediatric patients with beta thalassemia.

METHODS

Forty children with beta thalassemia major (TM), forty children with beta thalassemia intermedia (TI) and forty age and gender matched healthy controls were enrolled in this study. Detection of GNAI2, DUSP5 and ARRB1 mRNA expression was done by real time polymerase chain reaction (RT-PCR).

RESULTS

revealed increased expression of ARRB1 (Arrestin Beta 1) gene, and decreased expression of both GNAI2 (Guanine nucleotide-binding protein G (i) subunit alpha-2) and DUSP5 (Dual specificity protein phosphatase 5) genes in both patient groups than control groups respectively.

CONCLUSIONS

Change in the rate of expression of ARRB1, GNAI2 and DUSP5 may have a role in the pathogenesis of abnormal hematopoiesis in cases of β thalassemia through affecting the MAPK pathway.

XmnI Polymorphism in Sickle Cell Disease in North Morocco

Sickle cell disease is one of the most common severe monogenic disorders in the world. The -158 XmnI polymorphism (C>T) of the ^Gγ-globin gene promoter is known to be associated with increased expression of the ^Gγ-globin gene, thus, higher production of Hb F and lesser clinical severity. This study aims to determine the frequency of the XmnI polymorphism and its association with Hb F levels as a modulating factor of sickle cell disease severity in north Moroccan patients. Three hundred and eight subjects carrying the sickle cell mutation and 160 healthy individuals were recruited at the regional hospital of Larache, Morocco. The complete blood count and the Hb F levels were analyzed. The XmnI polymorphism was determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and statistical analysis were done using the Statistical Package for Social Sciences software version 20. Our results estimated the allelic frequency of the XmnI polymorphism in our population at 15.8%. Out of 468 samples, 7.6% were homozygous [+/+] and 16.4% were heterozygous [+/-] for the XmnI polymorphism. This polymorphism was revealed at 20.6% in SS patients, 24.2% in AS carriers, 28.6% in Hb S (HBB: c.20A>T)/β-thalassemia (β-thal) patients and 22.5% in AA subjects. The north Moroccan sickle cell disease patients have shown a low frequency of the XmnI polymorphism. This was later found to be associated with high Hb F levels and mild clinical severity.

Erythrocyte cAMP in Determining Frequency of Acute Pain Episodes in Sickle Cell Disease Patients from Odisha State, India

Vaso-occlusive crisis (VOC) occurs more frequently during stress in sickle cell disease patients. Epinephrine released during stress increases adhesion of sickled red blood cells (RBCs) to endothelium and to leukocytes, a process mediated through erythrocyte cyclic adenosine monophosphate (cAMP). Increased adhesion of sickled RBCs retards blood flow through the capillaries and promotes vaso-occlusion. Therefore, we examined the association of RBC-cAMP levels with frequency of acute pain episodes in sickle cell disease subjects. Using a case control study design, we measured RBC-cAMP levels, fetal hemoglobin (Hb F), α-thalassemia (α-thal) and other hematological parameters at baseline (sham treated) and after stimulation with epinephrine. The cases consisted of sickle cell disease subjects with three or more acute pain episodes in the last 12 months, and those without a single acute pain episode in the last 12 months were considered as controls. Significantly higher cAMP values were found in cases than the controls, in both sham treated (p < 0.001) and epinephrine treated RBCs (p < 0.001) by Wilcoxon Rank Sum test. However, significant association of cAMP values was observed both on univariate [odds ratio (OR): 4.8, 95% confidence interval (95% CI): 1.51-15.19, p < 0.008) and multivariate logistic regression analyses only in epinephrine treated (OR: 5.07, 95% CI: 1.53-16.82, p < 0.008) but not in sham-treated RBCs. In the covariates, Hb F consistently showed protective effects in univariate as well as in multivariate analyses. Frequent acute pain episodes are associated with higher cAMP levels than those with less frequent pain episodes, only after stimulation with epinephrine but not with baseline level.

Association of fetal hemoglobin level with frequency of acute pain episodes in sickle cell disease (HbS-only phenotype) patients

BACKGROUND

Sickle cell disease (SCD) is a Mendelian single gene disorder with highly variable phenotypic expression. In the present study, we analyzed the influence of HbF, alpha thalassemia and other hematological indices to determine their association with acute pain episodes.

METHOD

This case control study consisted of SCD subjects with HbS phenotype experiencing three or more acute pain episodes in last twelve months (cases) and without any episode of acute pain during last twelve months (controls). Hematological parameters, HbF, and presence of alpha thalassemia were assessed in all subjects.

RESULTS

A statistically significant difference between HbF levels (P < 0.025, χ2 test) and alpha thalassemia (P < 0.008, χ2 test) was observed between controls and cases group. Univariate analysis indicated that increased HbF levels > 25% (OR: 0.37, 95% CI: 0.18-0.77, P < 0.008) and presence of alpha thalassemia (OR: 0.53, 95% CI: 0.33-0.85, P < 0.009) provided protection, while multivariate analysis revealed significant protection was attributable only by higher HbF levels (OR: 0.39, 95% CI: 0.17-0.88, P < 0.025). Significantly higher HbF levels were observed only in the 11-20 age group of cases in comparison to controls (Student's t-test, P < 0.001).

CONCLUSION

Higher concentrations of HbF are associated with protection against frequent episodes of acute pain crisis in SCD patients.

βS globin gene haplotype and the stroke risk among Egyptian children with sickle cell disease

BACKGROUND AND AIM OF WORK

Sickle cell disease (SCD) is an inherited disease of the beta globin gene. The β^S globin gene haplotypes are Senegal, Benin, Bantu, Cameroon, Arab-Indian and atypical haplotypes. In SCD, stroke is a life-threatening event in both adults and children. In light of paucity of studies on β^S globin gene haplotypes in Egypt, we aimed to determine β^S globin gene haplotypes in children with SCD and study their impact on stroke risk.

METHODS

Fifty-two SCD patients were included in the study, they were 26 males and 26 females with age range from 3 to 18 years old. The PCR-RFLP technique was used for the determination of β^S globin gene haplotypes. Transcranial Doppler (TCD) was done to identify patients at risk of stroke.

RESULTS

Benin/Benin was the most prevalent haplotype detected in 50% followed by Benin/Bantu in 30.8% of studied patients. TCD study showed that 14/52 (26.9%) patients had abnormally high TCD flow velocities (TCD velocities ≥170 cm/s) and thus considered high stroke risk group, whereas 38/52 (73.1%) patients had TCD flow velocities <170 cm/s and are considered low stroke risk group. Stroke risk was not found to be associated with β^S globin gene haplotype (p = .532).

CONCLUSION

This study provides a relevant contribution to our understanding of the anthropological and historical background of the population in Egypt where Benin haplotype is the commonest β^S globin gene haplotype and homozygous Benin/Benin is associated with higher stroke risk than other haplotypes.

The orphan nuclear receptor TR4 regulates erythroid cell proliferation and maturation

The orphan nuclear receptors TR4 (NR2C2) and TR2 (NR2C1) are the DNA-binding subunits of the macromolecular complex, direct repeat erythroid-definitive, which has been shown to repress ε- and γ-globin transcription during adult definitive erythropoiesis. Previous studies implied that TR2 and TR4 act largely in a redundant manner during erythroid differentiation; however, during the course of routine genetic studies, we observed multiple variably penetrant phenotypes in the Tr4 mutants, suggesting that indirect effects of the mutation might be masked by multiple modifying genes. To test this hypothesis, Tr4^+/- mutant mice were bred into a congenic C57BL/6 background and their phenotypes were reexamined. Surprisingly, we found that homozygous Tr4 null mutant mice expired early during embryogenesis, around embryonic day 7.0, and well before erythropoiesis commences. We further found that Tr4^+/- erythroid cells failed to fully differentiate and exhibited diminished proliferative capacity. Analysis of Tr4^+/- mutant erythroid cells revealed that reduced TR4 abundance resulted in decreased expression of genes required for heme biosynthesis and erythroid differentiation (Alad and Alas2), but led to significantly increased expression of the proliferation inhibitory factor, cyclin dependent kinase inhibitor (Cdkn1c) These studies support a vital role for TR4 in promoting erythroid maturation and proliferation, and demonstrate that TR4 and TR2 execute distinct, individual functions during embryogenesis and erythroid differentiation.

Original Research: A case-control genome-wide association study identifies genetic modifiers of fetal hemoglobin in sickle cell disease

Sickle cell disease (SCD) is a group of inherited blood disorders that have in common a mutation in the sixth codon of the β-globin (HBB) gene on chromosome 11. However, people with the same genetic mutation display a wide range of clinical phenotypes. Fetal hemoglobin (HbF) expression is an important genetic modifier of SCD complications leading to milder symptoms and improved long-term survival. Therefore, we performed a genome-wide association study (GWAS) using a case-control experimental design in 244 African Americans with SCD to discover genetic factors associated with HbF expression. The case group consisted of subjects with HbF≥8.6% (133 samples) and control group subjects with HbF≤£3.1% (111 samples). Our GWAS results replicated SNPs previously identified in an erythroid-specific enhancer region located in the second intron of the BCL11A gene associated with HbF expression. In addition, we identified SNPs in the SPARC, GJC1, EFTUD2 and JAZF1 genes as novel candidates associated with HbF levels. To gain insights into mechanisms of globin gene regulation in the HBB locus, linkage disequilibrium (LD) and haplotype analyses were conducted. We observed strong LD in the low HbF group in contrast to a loss of LD and greater number of haplotypes in the high HbF group. A search of known HBB locus regulatory elements identified SNPs 5' of δ-globin located in an HbF silencing region. In particular, SNP rs4910736 created a binding site for a known transcription repressor GFi1 which is a candidate protein for further investigation. Another HbF-associated SNP, rs2855122 in the cAMP response element upstream of Gγ-globin, was analyzed for functional relevance. Studies performed with siRNA-mediated CREB binding protein (CBP) knockdown in primary erythroid cells demonstrated γ-globin activation and HbF induction, supporting a repressor role for CBP. This study identifies possible molecular determinants of HbF production.

Genomic approaches to identifying targets for treating β hemoglobinopathies

Sickle cell disease and β thalassemia are common severe diseases with little effective pathophysiologically-based treatment. Their phenotypic heterogeneity prompted genomic approaches to identify modifiers that ultimately might be exploited therapeutically. Fetal hemoglobin (HbF) is the major modulator of the phenotype of the β hemoglobinopathies. HbF inhibits deoxyHbS polymerization and in β thalassemia compensates for the reduction of HbA. The major success of genomics has been a better understanding the genetic regulation of HbF by identifying the major quantitative trait loci for this trait. If the targets identified can lead to means of increasing HbF to therapeutic levels in sufficient numbers of sickle or β-thalassemia erythrocytes, the pathophysiology of these diseases would be reversed. The availability of new target loci, high-throughput drug screening, and recent advances in genome editing provide the opportunity for new approaches to therapeutically increasing HbF production.

Role of XmnIgG Polymorphism in Hydroxyurea Treatment and Fetal Hemoglobin Level at Isfahanian Intermediate β-Thalassemia Patients

BACKGROUND

β-thalassemia is the most common monogenic disorder in human. The (C-->T) polymorphism at -158 upstream region of the γG-globin gene and pharmacological factors such as hydroxyurea have been reported to influence γ-globin gene expression and the severity of clinical symptoms of β-thalassemia.

METHODS

In the present study, 51 β-thalassemia intermediate patients were studied. Xmn1γG polymorphism genotype was determined using Tetra-Primer ARMS-PCR technique. Hemoglobin (Hb) and fetal hemoglobin (HbF) levels were determined by gel electrophoresis.

RESULTS

Of 51 patients, 35 (68.6%) patients were heterozygous (CT) and 16 (31.4%) patients were homozygous (CC). Of 30 patients under treatment by hydroxyurea, 20 (66.7%) patients were heterozygous (CT) and 10 (33.3%) patients were homozygous (CC). Our results demonstrated that in the heterozygous (CT) genotype, the Hb (9.58 ± 1.25 gm/dl) and HbF (89.30 ± 21.87) levels were significantly higher in comparison with homozygous (CC) genotype (7.94 ± 1.34 gm/dl and 70.32 ± 40.56, respectively). Furthermore, we observed that after drug usage, the Hb and HbF levels in patients with heterozygous (CT) genotype (0.7 ± 1.26 gm/dl and 5.95 ± 14.8, respectively) raised more in comparison with homozygous (CC) genotype (0.26 ± 1.43 gm/dl and 0.8 ± 1.31, respectively).

CONCLUSION

Hb and HbF levels in the patients carrying T allele are increased significantly, and they also response to hydroxyurea treatment.

Can STOP Trial Velocity Criteria Be Applied to Iranian Children with Sickle Cell Disease?

Background and Purpose

Sickle cell disease (SCD) is strongly linked to stroke across all haplotypes in the pediatric population. Transcranial Doppler (TCD) ultrasound is known to identify the highest risk group in African-Americans who need to receive and stay on blood transfusions, but it is unclear if the same flow velocity cut-offs can be applied to the Iranian population. We aimed to evaluate baseline TCD findings in Iranian children with SCD and no prior strokes.

Methods

Children with genetically confirmed SCD (Arabian haplotype, homozygote) and without SCD (controls) were prospectively recruited from pediatric outpatient clinic over a period of 9 months. We performed TCD in both groups to determine flow velocities in the middle cerebral (MCA) and terminal internal carotid arteries (TICA).

Results

Of 74 screened children, 60 met the inclusion/exclusion criteria (62% female; mean age 10±4 years). Baseline characteristics did not differ between the cases and controls, except hemoglobin (Hb) which was significantly lower in the SCD group (P<0.001). The right MCA TAMM (Time Averaged Maximum Mean) was significantly higher than in controls (125+5.52 cm/s vs. 92.5+1.63 cm/s, P<0.001). Left MCA did not show differences. The TICA TAMM was also different between cases and controls (P<0.05).

Conclusions

Among Iranian children with asymptomatic SCD and without receiving recent transfusion TCD velocities are higher as compared to healthy controls but appear much lower than those observed in STOP (Stroke Prevention Trial in Sickle Cell Anemia) studies. We hypothesize that some children at high risk may be present with velocities lower than 170-200 cm/s thresholds. A prospective validation of ethnicity-specific prognostic criteria is warranted.

A common signaling pathway is activated in erythroid cells expressing high levels of fetal hemoglobin: a potential role for cAMP-elevating agents in β-globin disorders

Background

Although erythroid cells prepared from fetal liver, cord blood, or blood from β-thalassemia patients are known to express fetal hemoglobin at high levels, the underlying mechanisms remain elusive. We previously showed that cyclic nucleotides such as cAMP and cGMP induce fetal hemoglobin expression in primary erythroid cells. Here we report that cAMP signaling contributes to high-level fetal hemoglobin expression in erythroid cells prepared from cord blood and β-thalassemia.

Methods

The status of the cAMP signaling pathway was investigated using primary erythroid cells prepared from cord blood and the mononuclear cells of patients with β-thalassemia; erythroid cells from adult bone marrow mononuclear cells served as the control.

Results

We found that intracellular cAMP levels were higher in erythroid cells from cord blood and β-thalassemia than from adult bone marrow. Protein kinase A activity levels and cAMP-response element binding protein phosphorylation were higher in erythroid cells from cord blood or β-thalassemia than in adult bone marrow progenitors. Mitogen-activated protein kinase pathways, which play a role in fetal hemoglobin expression, were not consistently activated in cord blood or β-thalassemia erythroid cells. When cAMP signaling was activated in adult erythroid cells, fetal hemoglobin was induced at high levels and associated with reduced expression of BCL11A, a silencer of the β-globin gene.

Conclusion

These results suggest that activated cAMP signaling may be a common mechanism among erythroid cells with high fetal hemoglobin levels, in part because of downregulation of BCL11A. Activation of the cAMP signaling pathway with cAMP-elevating agents may prove to be an important signaling mechanism to reactivate fetal hemoglobin expression in erythroid cells.

Fetal hemoglobin in sickle cell anemia: genetic studies of the Arab-Indian haplotype

Sickle cell anemia is common in the Middle East and India where the HbS gene is sometimes associated with the Arab-Indian (AI) β-globin gene (HBB) cluster haplotype. In this haplotype of sickle cell anemia, fetal hemoglobin (HbF) levels are 3-4 fold higher than those found in patients with HbS haplotypes of African origin. Little is known about the genetic elements that modulate HbF in AI haplotype patients. We therefore studied Saudi HbS homozygotes with the AI haplotype (mean HbF 19.2±7.0%, range 3.6 to 39.6%) and employed targeted genotyping of polymorphic sites to explore cis- and trans- acting elements associated with high HbF expression. We also described sequences which appear to be unique to the AI haplotype for which future functional studies are needed to further define their role in HbF modulation. All cases, regardless of HbF concentration, were homozygous for AI haplotype-specific elements cis to HBB. SNPs in BCL11A and HBS1L-MYB that were associated with HbF in other populations explained only 8.8% of the variation in HbF. KLF1 polymorphisms associated previously with high HbF were not present in the 44 patients tested. More than 90% of the HbF variance in sickle cell patients with the AI haplotype remains unexplained by the genetic loci that we studied. The dispersion of HbF levels among AI haplotype patients suggests that other genetic elements modulate the effects of the known cis- and trans-acting regulators. These regulatory elements, which remain to be discovered, might be specific in the Saudi and some other populations where HbF levels are especially high.

The proinflammatory cytokine GM-CSF downregulates fetal hemoglobin expression by attenuating the cAMP-dependent pathway in sickle cell disease

Although reduction in leukocyte counts following hydroxyurea therapy in sickle cell disease (SCD) predicts fetal hemoglobin (HbF) response, the underlying mechanism remains unknown. We previously reported that leukocyte counts are regulated by granulocyte-macrophage colony-stimulating factor (GM-CSF) in SCD patients. Here we examined the roles of GM-CSF in the regulation of HbF expression in SCD. Upon the analysis of retrospective data in 372 patients, HbF levels were inversely correlated with leukocyte counts and GM-CSF levels in SCD patients without hydroxyurea therapy, while HbF increments after hydroxyurea therapy correlated with a reduction in leukocyte counts, suggesting a negative effect of GM-CSF on HbF expression. Consistently, in vitro studies using primary erythroblasts showed that the addition of GM-CSF to erythroid cells decreased HbF expression. We next examined the intracellular signaling pathway through which GM-CSF reduced HbF expression. Treatment of erythroid cells with GM-CSF resulted in the reduction of intracellular cAMP levels and abrogated phosphorylation of cAMP response-element-binding-protein, suggesting attenuation of the cAMP-dependent pathway, while the phosphorylation levels of mitogen-activated protein kinases were not affected. This is compatible with our studies showing a role for the cAMP-dependent pathway in HbF expression. Together, these results demonstrate that GM-CSF plays a role in regulating both leukocyte count and HbF expression in SCD. Reduction in GM-CSF levels upon hydroxyurea therapy may be critical for efficient HbF induction. The results showing the involvement of GM-CSF in HbF expression may suggest possible mechanisms for hydroxyurea resistance in SCD.

Forced TR2/TR4 expression in sickle cell disease mice confers enhanced fetal hemoglobin synthesis and alleviated disease phenotypes

Sickle cell disease (SCD) is a hematologic disorder caused by a missense mutation in the adult β-globin gene. Higher fetal hemoglobin (HbF) levels in red blood cells of SCD patients have been shown to improve morbidity and mortality. We previously found that nuclear receptors TR2 and TR4 repress expression of the human embryonic ε-globin and fetal γ-globin genes in definitive erythroid cells. Because forced expression of TR2/TR4 in murine adult erythroid cells paradoxically enhanced fetal γ-globin gene expression in transgenic mice, we wished to determine if forced TR2/TR4 expression in a SCD model mouse would result in elevated HbF synthesis and thereby alleviate the disease phenotype. In a "humanized" sickle cell model mouse, forced TR2/TR4 expression increased HbF abundance from 7.6% of total hemoglobin to 18.6%, accompanied by increased hematocrit from 23% to 34% and reticulocyte reduction from 61% to 18%, indicating a significant reduction in hemolysis. Moreover, forced TR2/TR4 expression reduced hepatosplenomegaly and liver parenchymal necrosis and inflammation in SCD mice, indicating alleviation of usual pathophysiological characteristics. This article shows that genetic manipulation of nonglobin proteins, or transcription factors regulating globin gene expression, can ameliorate the disease phenotype in a SCD model animal. This proof-of-concept study demonstrates that modulating TR2/TR4 activity in SCD patients may be a promising therapeutic approach to induce persistent HbF accumulation and for treatment of the disease.

Fetal hemoglobin in sickle cell anemia

Fetal hemoglobin (HbF) is the major genetic modulator of the hematologic and clinical features of sickle cell disease, an effect mediated by its exclusion from the sickle hemoglobin polymer. Fetal hemoglobin genes are genetically regulated, and the level of HbF and its distribution among sickle erythrocytes is highly variable. Some patients with sickle cell disease have exceptionally high levels of HbF that are associated with the Senegal and Saudi-Indian haplotype of the HBB-like gene cluster; some patients with different haplotypes can have similarly high HbF. In these patients, high HbF is associated with generally milder but not asymptomatic disease. Studying these persons might provide additional insights into HbF gene regulation. HbF appears to benefit some complications of disease more than others. This might be related to the premature destruction of erythrocytes that do not contain HbF, even though the total HbF concentration is high. Recent insights into HbF regulation have spurred new efforts to induce high HbF levels in sickle cell disease beyond those achievable with the current limited repertory of HbF inducers.

High-density SNP genotyping to define beta-globin locus haplotypes

Five major beta-globin locus haplotypes have been established in individuals with sickle cell disease (SCD) from the Benin, Bantu, Senegal, Cameroon, and Arab-Indian populations. Historically, beta-haplotypes were established using restriction fragment length polymorphism (RFLP) analysis across the beta-locus, which consists of five functional beta-like globin genes located on chromosome 11. Previous attempts to correlate these haplotypes as robust predictors of clinical phenotypes observed in SCD have not been successful. We speculate that the coverage and distribution of the RFLP sites located proximal to or within the globin genes are not sufficiently dense to accurately reflect the complexity of this region. To test our hypothesis, we performed RFLP analysis and high-density single nucleotide polymorphism (SNP) genotyping across the beta-locus using DNA samples from healthy African Americans with either normal hemoglobin A (HbAA) or individuals with homozygous SS (HbSS) disease. Using the genotyping data from 88 SNPs and Haploview analysis, we generated a greater number of haplotypes than that observed with RFLP analysis alone. Furthermore, a unique pattern of long-range linkage disequilibrium between the locus control region and the beta-like globin genes was observed in the HbSS group. Interestingly, we observed multiple SNPs within the HindIII restriction site located in the Ggamma-globin intervening sequence II which produced the same RFLP pattern. These findings illustrated the inability of RFLP analysis to decipher the complexity of sequence variations that impacts genomic structure in this region. Our data suggest that high-density SNP mapping may be required to accurately define beta-haplotypes that correlate with the different clinical phenotypes observed in SCD.

Splenectomy reduces packed red cell transfusion requirement in children with sickle cell disease

PURPOSE

The purpose of the study was to measure the effect of splenectomy on packed-cell transfusion requirement in children with sickle cell disease.

METHODS

Thirty-seven sickle cell children who underwent splenectomies between January 2000 and May 2006 at a children's hospital were reviewed. Data were collected 6 months preoperatively to 12 months postsplenectomy. Paired t test, analysis of variance, and multivariable regression analyses were performed.

RESULTS

Of 37 children with median age 11 years (range, 2-18 years), 34 (21 males) had data that allowed analyses. Twenty-six had Hgb-SS, 5 had Hgb-SC, and 3 had Hgb S-Thal. Laparoscopic splenectomy was attempted in 36 and completed successfully in 34 (94% success). The number of units transfused decreased by 38% for 0 to 6 months and by 45% for 6 to 12 months postsplenectomy. Postoperatively, hematocrit levels increased and reticulocytes concurrently decreased with a reduction in transfusion clinic visits. The decrease in transfusion was not influenced by spleen weight, age, or hemoglobin type. Two children had acute chest syndrome (6%), and 1 had severe pneumonia (3%).

CONCLUSION

Laparoscopic splenectomy can be successfully completed in sickle cell children. Splenectomy significantly reduces the packed red cell transfusion requirement and frequency of clinic visits, in sickle cell children for at least 12 months postoperatively.

Regional cerebral blood flow in patients with sickle cell disease: study with single photon emission computed tomography

OBJECTIVE

Neurological complications have been reported in patients with sickle-cell disease (SCD) using positron emission tomography (PET), magnetic resonance imaging (MRI), and computed tomography (CT), but not with single photon emission computed tomography (SPECT). The objective of this study was to investigate brain perfusion in the patients with SCD using SPECT after technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO), was administered and compare the findings with those of demography, physical examination, MRI and hematological profile.

METHODS

The study involved 21 patients (12 males, 9 females, age at study 8-45 years) who were known to be having SCD for a duration of at least 5 years. The patients were not in acute crisis and had normal neurological assessments with no known history of stroke or transient ischemic episode or previous abnormal CT or MRI brain scan, and were right-handed. The brain SPECT was performed after intravenous injection of 740 MBq (20 mCi) 99mTc-HMPAO in adults or an appropriate dose in pediatric patients. The scans were visually interpreted by two nuclear medicine physicians and a decision was reached by consensus. An MRI done 3 months later was interpreted by a radiologist. The demographic data and hematological profile were obtained from the medical records of the patients.

RESULTS

Of the 21 patients, 7 (age 11-22 years) had brain perfusion deficit mostly in the frontal lobe either alone or in combination with temporal and/or parietal lobe. The MRI was abnormal in 2 patients. The brain perfusion deficit was not associated with the demographic data of the patients or hematological profiles.

CONCLUSIONS

The findings show that SPECT was useful in detecting brain perfusion deficit in SCD patients, and such an early detection may be clinically useful in the subsequent follow-up of such patients, since it is known that cerebral perfusion deficit can lead to silent infarct and/or overt stroke, and affect cognitive skills.

Expression of the gamma-globin gene is sustained by the cAMP-dependent pathway in beta-thalassaemia

The present study found that the cyclic adenosine monophosphate (cAMP)-dependent pathway efficiently induced gamma-globin expression in adult erythroblasts, and this pathway plays a role in gamma-globin gene (HBG) expression in beta-thalassaemia. Expression of HBG mRNA increased to about 46% of non-HBA mRNA in adult erythroblasts treated with forskolin, while a cyclic guanosine monophosphate (cGMP) analogue induced HBG mRNA to levels <20% of non-HBA mRNA. In patients with beta-thalassaemia intermedia, cAMP levels were elevated in both red blood cells and nucleated erythroblasts but no consistent elevation was found with cGMP levels. The transcription factor cAMP response element binding protein (CREB) was phosphorylated in nucleated erythroblasts and its phosphorylation levels correlated with HBG mRNA levels of the patients. Other signalling molecules, such as mitogen-activated protein kinases and signal transducers and activators of transcription proteins, were phosphorylated at variable levels and showed no correlations with the HBG mRNA levels. Plasma levels of cytokines, such as erythropoietin, stem cell factor and transforming growth factor-beta were increased in patients, and these cytokines induced both HBG mRNA expression and CREB phosphorylation. These results demonstrate that the cAMP-dependent pathway, the activity of which is augmented by multiple cytokines, plays a role in regulating HBG expression in beta-thalassaemia.

Hemoglobin binding to A beta and HBG2 SNP association suggest a role in Alzheimer's disease

From a normal human brain phage display library screen we identified the gamma (A)-globin chain of fetal hemoglobin (Hb F) as a protein that bound strongly to A beta1-42. We showed the oxidized form of adult Hb (metHb A) binds with greater affinity to A beta1-42 than metHb F. MetHb is more toxic than oxyhemoglobin because it loses its heme group more readily. Free Hb and heme readily damage vascular endothelial cells similar to Alzheimer's disease (AD) vascular pathology. The XmnI polymorphism (C-->T) at -158 of the gamma (G)-globin promoter region can contribute to increased Hb F expression. Using family-based association testing, we found a significant protective association of this polymorphism in the NIMH sibling dataset (n=489) in families, with at least two affected and one unaffected sibling (p=0.006), with an age of onset >50 years (p=0.010) and >65 years (p=0.013), and families not homozygous for the APOE4 allele (p=0.041). We hypothesize that Hb F may be less toxic than adult Hb in its interaction with A beta and may protect against the development of AD.

UGT1A1 polymorphism outweighs the modest effect of deletional (-3.7 kb) alpha-thalassemia on cholelithogenesis in sickle cell anemia

Enhanced erythrocyte destruction in sickle cell anemia results in chronic hyperbilirubinemia. Only a subset of patients develop cholelithiasis. UGT1A1 promoter polymorphism is associated both with unconjugated bilirubin level and elevated risk for cholelithiasis in such subset. Here, we investigated the role of alpha-thalassemia, yet another genetic factor that modulates hemolysis, in conferring protection from cholelithiasis. We show that, although alpha-thalassemia is associated with modest reduction in hemolysis and unconjugated bilirubin level, UGT1A1 polymorphism outweighs its effect on cholethiogenesis in sickle cell anemia patients.

Hemoglobinopathies mimicking Hb S/beta-thalassemia: Hb S/S with alpha-thalassemia and Hb S/Volga

There are approximately 1200 known natural mutations of the human globin genes. In most clinical laboratories, the diagnosis of hemoglobin disorders is based on blood counts, hemoglobin electrophoresis, or column chromatography, which can identify common variant hemoglobins such as Hb S, C, and E, but are unable to definitively diagnose most other hemoglobin variants and thalassemia mutations. We report two unrelated cases, both thought initially to have Hb S/beta-thalassemia. Subsequent mutational analyses revealed that one is Hb S/S with compound heterozygosity for nondeletional alpha-thalassemia mutations. The other is the first reported case of compound heterozygosity for Hb S and an unstable hemoglobin, Hb Volga. Correct diagnoses of these hereditary disorders are needed for prognosis and proper management and also for genetic counseling. These studies underscore the importance to correlate clinical course with laboratory diagnosis and to make DNA-based diagnostics more widely available for patients with unusual or complicated hemoglobin disorders.

Thalassemia: The Continued Challenge

This overview describes the history of transfusion therapy and consequent iron overload in thalassemia. It emphasizes the importance of measurement of hepatic iron and reviews the history of chelation therapy. It briefly describes the discoveries of the genetic basis of thalassemia and the application of that knowledge in prenatal diagnosis. The review goes on to emphasize pharmaceutical efforts to induce fetal hemoglobin synthesis in thalassemic red cells and ends with a discussion of oral iron chelators, stem cell transplant, and the status of gene therapy.

Silent brain infarcts in adult Kuwaiti sickle cell disease patients

Although overt stroke is a common complication of sickle cell disease (SCD), its incidence is very low in Kuwaiti patients. On the other hand, the prevalence of silent brain infarcts, which is reported to be about 17-20% in American patients, has not been documented in adult Kuwaiti patients. This is a 1-year study of consecutive, asymptomatic SCD patients seen in the hematology clinic of Mubarak Al-Kabeer Hospital. Patients with a past history of seizure or any other neurological abnormality were excluded. The patients' charts were reviewed for frequency of hospitalizations, any documented complications, and steady-state CBC. MRI was done with a 1.5-Tesla unit with super-conducting magnet. T1- and T2-weighted sagittal and axial sections and proton-density axial images were obtained in 5-mm-thick sections. Thirty-five patients were studied, made up of 25 SS and 10 Sbeta(0)Thal, aged between 17 and 44 years, with a mean age of 26.9 +/- 9.3 years. MRI findings consistent with infarcts were found in 7 (20.0%) patients-6 SS and 1 Sbeta(0)thal-with a mean age of 31.8 +/- 8.2 years, which was significantly higher (P < 0.05) than the mean age of the unaffected group (25.1 - 9.0 years). There were also no differences in the mean Hb, Hb F, or any other hematological parameter in the two groups. Among the affected 6 SS, 2 had co-existent alpha-thal trait. It is interesting that, while silent infarcts are prevalent in young American patients, it is in the older age group that they occur in Kuwaiti patients. Further studies are needed to investigate the factors modulating this heterogeneity.

Fetal hemoglobin elevation in Hb Lepore heterozygotes and its correlation with beta globin cluster linked determinants

We have analysed, at the hematological and molecular level, 51 Hb lepore heterozygotes and three compound heterozygotes for Hb Lepore and HbS (HbLep/HbS) in 26 unselected Portuguese families. The Lepore Boston variant was present in one family, in association with classical haplotype V. All of the other Lepore alleles present haplotype III in association with XmnI (+)5' of (G)gamma gene, in tight linkage disequilibrium to the major mutation found in the Portuguese population, the Lepore Baltimore variant ( delta(68Leu)-beta(84Thr)). The three compound heterozygotes are the first HbLep/HbS individuals reported in the literature, with the Lepore Baltimore mutation linked to haplotype III. In agreement with other studies, these Lepore Baltimore heterozygotes have higher HbF (1.4-14.1% of total hemoglobin) than published cases of Lepore Boston (0.8-5.4%), which is associated with XmnI(-). Among the Lepore Baltimore heterozygotes, the (AT)xTy repeat region at -540 bp of the beta globin gene in trans to the Lepore chromosome, can account for much of the variability in HbF level. The allele (AT)7T7 is associated with lower HbF, and (AT)9T5 is associated with higher HbF. As we previously reported for beta thalassemic carriers, we observe in Lepore Baltimore carriers an effector in trans, linked to the (AT)xTy sequence, acting as an HPFH (Hereditary Persistence of Fetal Hemoglobin) determinant.

Temporal sequence of splenic dysfunction in sickle cell disease

Sickle cell patients develop splenic dysfunction early in the course of their disease as shown by failure to visualize the organ on technetium-99m colloid scintigraphy. However, preliminary studies from our center have shown that, when the spleen is not demonstrable on colloid uptake, it may be visualized on technetium-99m heat-denatured RBC scintigraphy. With time, however, the spleen can no longer be visualized with both tests in many patients. We have studied 46 patients aged 2 to 16 years, which included 36 SS, 7 Sbeta(0) thal, and 3 SD. Eighteen (39.1%) had normal splenic colloid uptake (Group 1), 15 (32.6%) had partial uptake (Group 2), and 13 (28.3%) had absent uptake (Group 3). When the patients in Group 1 were compared to those in the two other groups, there was no significant difference in the mean age and Hb F values. However, the mean Hb of 10.2 g/dl in Group 1 was significantly higher than the value of 9.0 g/dl in the other two groups. In addition, 60% of the SS patients with normal uptake and 40% of those with partial or absent uptake had co-existing alpha-thal trait; the difference in this proportion is significant (chi(2) = 85, P < 0.0001). Heat-denatured RBC scintigraphy was carried out on five patients in Group 2, and the spleen was visible in all, while of 12 children in Group 3, the spleen was visible only in 4 patients. This study demonstrates that the phagocytic function of the spleen, which is tested by colloid uptake, is the first to be lost while the filtration function, tested by denatured RBC uptake, persists for much longer. This finding may have significant implications for the clinical symptomatology and therapeutic strategies of sickle cell disease.

Pathophysiology of sickle cell disease: role of cellular and genetic modifiers

Sickle hemoglobin (HbS), caused by a point mutation in the beta-globin gene of hemoglobin, polymerizes when deoxygenated. The pathophysiology of sickle cell disease results from cellular defects caused directly by the hemoglobin mutation interacting with the environment and many other gene products--a few known, but most yet unidentified--a typical example of epistasis. How normal tissue perfusion is interrupted is complex and why the phenotype of sickle cell disease differs from patient to patient is poorly understood. We review the "classic" aspects of the pathophysiology of sickle cell disease and focus on known and potential modulators of the phenotype of this disorder.

Modulation of fetal hemoglobin in sickle cell anemia

A partial understanding of the pathophysiology of sickle cell disease has suggested one means of treatment-increasing the distribution and concentration of fetal hemoglobin in sickle erythrocytes. Although this can be accomplished clinically with drugs like hydroxyurea, a complete understanding of the molecular and cellular basis of fetal hemoglobin regulation may suggest new and better ways of attaining this goal.

Genetic factors affecting clinical severity in beta-thalassemia syndromes

PURPOSE

Heterogeneity in the clinical manifestation of beta-thalassemic diseases may occur from the nature of beta-globin gene mutations, alpha-thalassemia gene interaction, or differences in the amount of hemoglobin (Hb) F production. This study was conducted to determine whether these genetic determinant factors can predict phenotypic severity of patients with beta-thalassemia and to assess the relationship between the genotype and phenotype of the disease.

MATERIALS AND METHODS

A total of 144 patients with beta-thalassemia were divided into mild (46 patients), intermediate (55 patients), and severe groups (43 patients). DNA analysis based on polymerase chain reaction technique was performed to characterize types of beta-thalassemia mutation, interaction of alpha-thalassemia, and XmnI polymorphism 5' to Ggamma-globin gene.

RESULTS

Two alleles of mild beta-thalassemia mutation (beta+/beta+-thalassemia or beta+-thalassemia/Hb E) resulted in a mild clinical symptom whereas two alleles of severe beta-thalassemia mutation (betao/betao) produced a severe clinical phenotype. Compound heterozygosity for mild and severe alleles of beta-thalassemia (betao/ beta+-thalassemia or betao-thalassemia/Hb E) led to variable severity of anemia. Coinheritance of alpha-thalassemia alleviated the severity of beta-thalassemia disease in those patients with at least one allele of the mild beta-thalassemia genotype. DNA polymorphism at position-158 nt 5' to the Ggamma-globin gene was demonstrated by XmnI restriction enzyme. Homozygote of the XmnI site, +/+, was found to have a strong linkage with high Hb F levels and high hemoglobin production in two patients who had mild clinical symptoms. However, some patients who had XmnI site -/- also had mild clinical symptoms because the XmnI- was found to be associated with beta+-thalassemia mutation.

CONCLUSION

Types of beta-thalassemia mutation and coinheritance of alpha-thalassemia in the patient who has at least one allele of the mild beta-thalassemia genotype are predictive for the clinical severity of the disease. However, a mild clinical symptom in some patients with betao/beta+-thalassemia or betao-thalassemia/Hb E who do not have a detectable alpha-thalassemia haplotype and no linkage with XmnI++ suggests that there are other confounding factors responsible for the severity differences of the disease.

Tumor necrosis factor-alpha is undetectable in the plasma of SS patients with elevated Hb F

Steady-state sickle cell disease (SCD) patients may have increased plasma levels of acute phase reactants and pro-inflammatory cytokines because of subclinical inflammation. We have estimated TNF-alpha levels in the plasma and in supernatants following peripheral blood mononuclear cell (PBMC) activation with phytohemagglutinin (PHA) in a group of Kuwaiti SCD patients using ELISA. The group consisted of 28 SS, 8 Sbeta-thal, and 2 SD patients all in steady state; 5 SS patients were studied during 7 episodes of painful crisis. The subjects were aged 2 to 16 years, with a mean of 7.3 +/- 3.5 years. The beta(S)-globin gene cluster haplotype, alpha-tha1 status, and spleen function were determined in the SS group using standard techniques. Most (82%) were homozygous for the Saudi Arabia/India haplotype and had elevated Hb F levels ranging from 15% to 35%. There were 24 controls (Hb AA or AS), of whom 14 were healthy and 10 were acutely ill at the time of the study. None of the children with SCD (either in steady state or crisis) had detectable plasma TNF-alpha, but four controls (3 acutely ill and one healthy) had levels ranging from 61.7 to 249.8 pg/mL. Following PHA stimulation most subjects responded with high levels of TNF-alpha, with the median level among the steady-state SS patients being significantly higher than that in the controls (both the acutely ill or healthy). It therefore appears that because of the mild disease among our Arab SS children, TNF-alpha is not detectable in their plasma in steady state; these children, however, had a significantly higher response than controls following PBMC activation.

Genetic modifying factors in beta-thalassemia

The beta-thalassemia is probably the most extensively studied genetic disease. Essentially any molecular defect that has been first described in association with the globin genes has been later implicated as a molecular determinant of newly discovered genes. Accordingly, the thalassemias have always represented a model genetic disease, especially in relation to the development of programs for population screening, genetic counseling and prenatal diagnosis. Here we will review the present knowledge on the genetics of thalassemia and of the relevant modifying factors. Major categories of the carrier state, the genotypes, the clinical phenotypes and the correlation between genotype and phenotype will be discussed.

Localisation of cis regulatory elements at the beta-globin locus: analysis of hybrid haplotype chromosomes

Several cis elements at the beta-globin gene cluster and the upstream locus control region (LCR) have been implicated in modulation of fetal haemoglobin (Hb F) level in beta-globin disorders. To determine the role of elements at the LCR and the beta-globin gene cluster on HbF level among sickle cell anaemia (SCA) patients, hybrid haplotype betaS chromosomes exhibiting variation in the association of alleles of LCR hypersensitive site 2 (HS2) and the beta-globin gene cluster restriction fragment length polymorphosim (RFLP) haplotypes were identified in an unselected population of 100 patients. On 15 chromosomes the polymorphic HS2 short tandem repeat(TA)xN10-12(TA)y containing a Hox2 binding motif differed from that typically associated with the corresponding beta-globin gene cluster RFLP haplotype. Among patients homozygous for the Benin RFLP haplotype, in whom one chromosome carried the (TA)9N10(TA)10 allele, no effect on HbF level was observed. Polymorphism of the pre-Ggamma framework, an enhancer located 25 kb downstream of HS2 localised the breakpoint for each of these 'hybrid' haplotype chromosomes upstream of this element. Previously described hybrid haplotype chromosomes with the (TA)9N10(TA)10 HS2 allele associated with raised HbF by contrast arise by recombination 1 kb downstream of the pre-Ggamma framework. This study suggests that variability in HbF level associated with polymorphisn of the HS2 enhancer depend on downstream determinant (s) in tight linkage disequilibrium with HS2. The pre-Ggamma framework is the only known polymorphic cis-active determinant in this region.

Hematological effects of atypical and Cameroon beta-globin gene haplotypes in adult sickle cell anemia

To examine the effects of unusual or atypical beta-globin gene cluster haplotypes on the hematological features and Hb F levels of sickle cell anemia, we studied African Americans who had an atypical or Cameroon haplotype chromosome in association with a typical haplotype. We identified over 20 atypical haplotypes. The distribution of 5' sub-haplotypes of the atypical chromosomes mirrored the distribution of common haplotypes in African Americans with sickle cell anemia. Neither 5' nor 3' subhaplotypes of the atypical chromosomes affected Hb F levels, packed cell volume, or mean corpuscular volume in individuals with a Benin chromosome. That the 5' subhaplotype is unaffected might be a consequence of the small numbers of Senegal 5' subhaplotypes in our sample, the need for linkage of both 5' and 3' subhaplotypes of any haplotype for an effect on Hb F to be present, or the likelihood that a normal beta-globin gene contributed the 5' subhaplotypes of some atypical haplotypes.

Elimination of transfusions through induction of fetal hemoglobin synthesis in Cooley's anemia

Pharmacological stimulation of fetal hemoglobin production is of considerable interest as an alternative approach to therapy for Cooley's anemia. While intravenous compounds have been effective in inducing short-term increases in fetal hemoglobin in a few patients, long-term elimination of transfusion requirement has not been reported. In patients with Cooley's anemia, treatment with oral sodium phenylbutyrate alone, sodium phenylbytyrate combined with hydroxyurea, and hydroxyurea alone, has augmented fetal hemoglobin production and increased total hemoglobin concentration as much as 5 g/dl over baseline eliminating transfusion requirement in two patients. Parallel declines in circulating nucleated red cell count, and concentrations of serum transform receptor and erythropoietin, are consistent with more effective erythropoiesis. Over extended periods of treatment, no induction of other fetal proteins and no adverse effects were observed. Particular disease mutations and other genetic factors may be of prime importance in determining the response to agents that induce production of fetal hemoglobin.

Pathophysiology of sickle cell disease

Sickle cell disease is caused by a mutation in the beta-globin chain of the haemoglobin molecule. Sickle haemoglobin, the result of this mutation, has the singular property of polymerizing when deoxygenated. Exactly how normal tissue perfusion is interrupted by abnormal sickle cells is complex and poorly understood. Despite genetic identity at the site of the sickle haemoglobin mutation, all patients with sickle cell anaemia are not affected equally by this disease. Secondary genetic determinants and acquired erythrocyte and vascular damage are likely to be central components of the pathophysiology of sickle cell anaemia.

Analysis of mRNA from red cells of patients with thalassemia and hemoglobin variants

During the past decade new procedures have been developed for the isolation of RNA from a few mL of freshly collected blood. This material is reverse transcribed and the resulting cDNA can be used for the determination of the ratios between different types of globin mRNA, namely alpha 2/alpha 1, alpha/zeta, alpha/beta, gamma/beta, beta A/beta X, delta beta Lep/beta, and G gamma/A gamma. Details about these polymerase chain reaction-based methods are reviewed, and information about their usefulness in studying alpha-thalassemia, beta-thalassemia, sickle cell anemia and other beta-globin gene abnormalities, Hb Lepore heterozygosity, and heterozygosity for alpha 2- or alpha 1-globin gene mutations will be provided. The methods are also most useful in characterizing the mRNA types in single, in vitro cultured, BFU-E colonies; in colonies derived from cells of a Hb S heterozygote; for instance, the beta A- and beta(S)-mRNAs were present in all colonies and in about equal quantities, while many of those cells from a subject with a somatic cell mutant (Hb Costa Rica) contained beta A-mRNA and no beta-Costa Rica mRNA, and only a few had both types. The techniques described have considerable diagnostic value and offer a rather simple approach to the study of some of the listed diseases.

Fetal hemoglobin in sickle cell anemia: examination of phylogenetically conserved sequences within the locus control region but outside the cores of hypersensitive sites 2 and 3

Regulatory elements linked to the beta-globin gene cluster modulates gamma-globin gene expression. The location of all of these elements and their mechanisms of action are still incompletely defined. Phylogenetically conserved DNA within the beta-globin gene cluster locus control region (LCR), but outside the core sequences of its hypersensitive sites (HS), were identified and we searched for any differences between HS 3 and HS 2, and HS 2 and HS 1, among patients with sickle cell anemia with different levels of Hb F who were homozygous for the common haplotypes. DNA was amplified with and without GC clamps, digested with restriction endonucleases, and examined by denaturing gradient gel electrophoresis (DGGE). We found limited fragment size diversity. However, the type of differences found and their distribution among haplotypes did not suggest that they represented distinctive changes that might explain the differential expression of the gamma-globin genes in sickle cell anemia.

Influence of alpha-thalassemia trait on spleen function in sickle cell anemia patients with high HbF

Spleen function was studied in a group of 20 Kuwaiti SS patients (aged 2-12 years), using 99mTc-labeled tin colloid scintigraphy. They were screened for the alpha-thalassemia determinants which are prevalent in the Arabian Peninsula [-alpha (3.7 kb) deletion, alpha2-globin gene polyadenylation signal (AATAAA => AATAAG) mutation, and 5' IVS-I splice junction pentanucleotide (GAGGTGAGG => GAGG) deletion] with a combination of polymerase chain reaction and allele-specific oligonucleotide (ASO) hybridization techniques. The patients were divided into three groups depending on the result of their colloid uptake. Group I consisted of 7 patients (35.0%) with normally visualized spleens, Group II consisted of 5 (25.0%) with partial visualization, and in Group III there were 8 (40.0%) in whom the spleen was not visualized at all. The significant distinguishing features among those in Groups I and III were mean corpuscular volumes (MCVs) of 74.1 +/- 5.1 and 90.1 +/- 6.6 fl (P<0.0001) and mean corpuscular hemoglobins (MCHs) of 22.4 +/- 2.7 and 27.5 +/- 4.0 pg (P<0.05), respectively. The overall frequency of alpha-thalassemia determinants in the study was 35.0%; however, the frequencies in Groups I, II, and III were 57.1, 30.0, and 18.8%, respectively. alpha-Thalassemia trait, therefore, appears to be associated with normal splenic function in these patients.

Modulation of the phenotypic diversity of sickle cell anemia

Sickle cell anemia is noted for being phenotypically heterogeneous. This suggests that there are genetic influences that moderate the effects of the sickle hemoglobin mutation. In this review I focus on genetically determined modulation of hemoglobin concentration and fetal hemoglobin levels. Each of these variables has important influences upon sickle hemoglobin polymerization and the resulting pathophysiology.

Extended therapy with intravenous arginine butyrate in patients with beta-hemoglobinopathies

BACKGROUND

Enhanced production of fetal hemoglobin lessens the severity of beta-thalassemia and sickle cell disease. Intravenous infusion of arginine butyrate can increase the number of reticulocytes containing fetal hemoglobin in patients with these disorders, and it has induced a substantial increase in hemoglobin in one patient with thalassemia. We therefore tested the efficacy of this agent in patients with beta-hemoglobinopathies.

METHODS

We treated 10 patients with severe beta-thalassemia or sickle cell disease with arginine butyrate at an initial dose of 500 mg per kilogram of body weight per day (final dose, 2000 mg per kilogram per day), 6 days per week, for a mean (+/- SD) of 10 +/- 1.2 weeks (range, 9 to 13). A hematologic response was defined as an increase in the hemoglobin concentration of at least 2 g per deciliter in patients with thalassemia and as a twofold increase in the fetal hemoglobin concentration in patients with sickle cell disease.

RESULTS

Increase in gamma-globin messenger RNA and in reticulocytes containing fetal hemoglobin but not in hemoglobin were observed in the patients with thalassemia. A small, unsustained increase in fetal hemoglobin was observed in two patients with sickle cell disease. Drug toxicity was minimal at standard doses. One patient had a grand mal seizure after inadvertently receiving 2000 mg of arginine butyrate per kilogram over a period of six hours.

CONCLUSIONS

Ten weeks of intravenous arginine butyrate did not produce a hematologic response in 10 patients with either severe beta-thalassemia or sickle cell disease.

Sickle cell gene in Central India: Kinship and geography

A wide range of variation (0.00-0.14) in the frequencies of the HbS allele has been observed among 16 tribes of Orissa, Madhya Pradesh, and Maharashtra. A significant excess of SS individuals over that expected under Hardy-Weinberg equilibrium was observed among 6 of 16 populations. These populations belong to three linguistic groups and have history of heterogeneous origins. A geographical cline of increase in HbS allele frequency from east to west is apparent. This pattern can largely be explained by differential migration. The kinship coefficient (r_ij ) and paired F_ST do not show any significant correleation up to 250 km of geographical distance but beyond this distance they show an inverse releationship with increasing geographic distance. Hemoglobin levels between individuals with β^S allele and with normal HbA individuals do not differ in these. © 1995 Wiley-Liss, Inc.