Beta-thalassaemia

Prenatal Diagnosis of Cystic Fibrosis by Celocentesis

Celocentesis is a new sampling tool for prenatal diagnosis available from 7 weeks in case of couples at risk for genetic diseases. In this study, we reported the feasibility of earlier prenatal diagnosis by celocentesis in four cases of cystic fibrosis and one case of cystic fibrosis and β-thalassemia co-inherited in the same fetus. Celomic fluids were aspired from the celomic cavity between 8+2 and 9+3 weeks of gestation and fetal cells were picked up by micromanipulator. Maternal DNA contamination was tested and target regions of fetal DNA containing parental pathogenetic variants of CFTR and HBB genes were amplified and sequenced. Four of the five fetuses resulted as being affected by cystic fibrosis and, in all cases, the women decided to interrupt the pregnancy. In the other case, the fetus presented a healthy carrier of cystic fibrosis. The results were confirmed in three cases on placental tissue. In one case, no abortive tissue was obtained. In the last case, the woman refused the prenatal diagnosis to confirm the celocentesis data; the pregnancy is ongoing without complications. This procedure provides prenatal diagnosis of monogenic diseases at least four weeks earlier than traditional procedures, reducing the anxiety of patients and providing the option for medical termination of the affected fetus at 8-10 weeks of gestation, which is less traumatic and safer than surgical termination in the second trimester.

An Update on the Application of CRISPR Technology in Clinical Practice

The CRISPR/Cas system, an innovative gene-editing tool, is emerging as a promising technique for genome modifications. This straightforward technique was created based on the prokaryotic adaptive immune defense mechanism and employed in the studies on human diseases that proved enormous therapeutic potential. A genetically unique patient mutation in the process of gene therapy can be corrected by the CRISPR method to treat diseases that traditional methods were unable to cure. However, introduction of CRISPR/Cas9 into the clinic will be challenging because we still need to improve the technology's effectiveness, precision, and applications. In this review, we first describe the function and applications of the CRISPR-Cas9 system. We next delineate how this technology could be utilized for gene therapy of various human disorders, including cancer and infectious diseases and highlight the promising examples in the field. Finally, we document current challenges and the potential solutions to overcome these obstacles for the effective use of CRISPR-Cas9 in clinical practice.

A New Perspective for Potential Organ Damage Due to Iron-Mediated Oxidation in Thalassemia Major Patients

BACKGROUND

The aim of this study is to develop new perspectives to prevent or reduce potential organ damage due to iron-mediated oxidation in thalassemia major patients.

METHODS

Seventy patients were included in this study. Blood samples were taken from the patients before and after transfusion. Total thiol, native thiol, disulfide, disulfide/native thiol percentage ratio, ischemia modified albumin (IMA), total antioxidant status (TAS), total oxidant status (TOS), and ferroxidase levels were determined. Additionally, undepleted thiol level (UTL) was determined as a new parameter associated with organ damage.

RESULTS

After transfusion, the levels of native thiol, total thiol, disulfide, TAS, ferroxidase, and TOS were higher, while the IMA levels and disulfide/native thiol percent ratio were lower. Significant correlations were found between antioxidant and oxidant tests before and after transfusion. Additionally, a negative correlation was found between the TOS and UTL levels of the patients measured before the transfusion.

CONCLUSION

In the present study, transfusion therapy increased both oxidation and the antioxidant levels. In addition, the term UTL has been introduced as a parameter that enables the determination of the oxidation level that may cause potential organ damage in transfusion-dependent thalassemia patients.

The Future of Gene Therapy for Transfusion-Dependent Beta-Thalassemia: The Power of the Lentiviral Vector for Genetically Modified Hematopoietic Stem Cells

β-thalassemia, a disease that results from defects in β-globin synthesis, leads to an imbalance of β- and α-globin chains and an excess of α chains. Defective erythroid maturation, ineffective erythropoiesis, and shortened red blood cell survival are commonly observed in most β-thalassemia patients. In severe cases, blood transfusion is considered as a mainstay therapy; however, regular blood transfusions result in chronic iron overload with life-threatening complications, e.g., endocrine dysfunction, cardiomyopathy, liver disease, and ultimately premature death. Therefore, transplantation of healthy hematopoietic stem cells (HSCs) is considered an alternative treatment. Patients with a compatible human leukocyte antigen (HLA) matched donor can be cured by allogeneic HSC transplantation. However, some recipients faced a high risk of morbidity/mortality due to graft versus host disease or graft failure, while a majority of patients do not have such HLA match-related donors. Currently, the infusion of autologous HSCs modified with a lentiviral vector expressing the β-globin gene into the erythroid progenitors of the patient is a promising approach to completely cure β-thalassemia. Here, we discuss a history of β-thalassemia treatments and limitations, in particular the development of β-globin lentiviral vectors, with emphasis on clinical applications and future perspectives in a new era of medicine.

Manipulation of Developmental Gamma-Globin Gene Expression: an Approach for Healing Hemoglobinopathies

β-Hemoglobinopathies are the most common monogenic disorders, and a century of research has provided us with a better understanding of the attributes of these diseases. Allogenic stem cell transplantation was the only potentially curative option available for these diseases until the discovery of gene therapy. The findings on the protective nature of fetal hemoglobin in sickle cell disease (SCD) and thalassemia patients carrying hereditary persistence of fetal hemoglobin (HPFH) mutations has given us the best evidence that the cure for β-hemoglobinopathies remains hidden in the hemoglobin locus. The detailed understanding of the developmental gene regulation of gamma-globin (γ-globin) and the emergence of gene manipulation strategies offer us the opportunity for developing a γ-globin gene-modified autologous stem cell transplantation therapy. In this review, we summarize different therapeutic strategies that reactivate fetal hemoglobin for the gene therapy of β-hemoglobinopathies.

Molecular Characterisation of α- and β-Thalassaemia among Indigenous Senoi Orang Asli Communities in Peninsular Malaysia

Thalassaemia is a public health problem in Malaysia, with each ethnic group having their own common mutations. However, there is a lack on data on the prevalence and common mutations among the indigenous people. This cross-sectional study was performed to determine the common mutations of α- and β-thalassaemia among the subethnic groups of Senoi, the largest Orang Asli group in Peninsular Malaysia. Blood samples collected from six Senoi subethnic groups were analysed for full blood count and haemoglobin analysis (HbAn). Samples with abnormal findings were then screened for α- and β-globin gene mutations. Out of the 752 samples collected, 255 showed abnormal HbAn results, and 122 cases showing abnormal red cell indices with normal HbAn findings were subjected to molecular screening. DNA analysis revealed a mixture of α- and β-globin gene mutations with 25 concomitant cases. The types of gene abnormalities detected for α-thalassaemia were termination codon (T>C) Hb CS (α^CS α), Cd59 (G>A) haemoglobin Adana (Hb Adana) (α^Cd59 α), initiation codon (ATG>A-G) (α^IniCd α), two-gene deletion (-^SEA ), and single-gene 3.7-kb deletion (-α^3.7 ). For β-thalassaemia, there were Cd26 (G>A) Hb E (β^E ), Cd19 (A>G) Haemoglobin Malay (Hb Malay) (β^Cd19 ), and IVS 1-5 (G>C) (β^{IVS 1-5} ).

Development of a High-Resolution Melting Approach for Scanning Beta Globin Gene Point Mutations in the Greek and Other Mediterranean Populations

Beta-thalassaemia is one of the most common autosomal recessive disorders worldwide. The disease’s high incidence, which is observed in the broader Mediterranean area has led to the establishment of molecular diagnostics’ assays to prevent affected births. Therefore, the development of a reliable, cost-effective and rapid scanning method for β globin gene point mutations, easily adapted to a routine laboratory, is absolutely essential. Here, we describe, for the first time, the development of a High-Resolution Melting Analysis (HRMA) approach, suitable for scanning the particularly heterogeneous beta globin gene mutations present in the Greek population, and thus adaptable to the Mediterranean and other areas where these mutations have been identified. Within this context, β globin gene regions containing mutations frequently identified in the Greek population were divided in ten overlapping amplicons. Our reactions’ setup allowed for the simultaneous amplification of multiple primer sets and partial multiplexing, thereby resulting in significant reduction of the experimental time. DNA samples from β-thalassaemia patients/carriers with defined genotypes were tested. Distinct genotypes displayed distinguishable melting curves, enabling accurate detection of mutations. The described HRMA can be adapted to a high-throughput level. It represents a rapid, simple, cost-effective, reliable, highly feasible and sensitive method for β-thalassaemia gene scanning.

Setup of a Protocol of Molecular Diagnosis of β-Thalassemia Mutations in Tunisia using Denaturing High-Performance Liquid Chromatography (DHPLC)

BACKGROUNDS

β-Thalassemia is one of the most prevalent worldwide autosomal recessive disorders. It presents a great molecular heterogeneity resulting from more than 200 causative mutations in the β-globin gene. In Tunisia, β-thalassemia represents the most prevalent monogenic hemoglobin disorder with 2.21% of carriers. Efficient and reliable mutation-screening methods are essential in order to establish appropriate prevention programs for at risk couples. The aim of the present study is to develop an efficient method based on the denaturing high-performance liquid chromatography (DHPLC) in which the whole β-globin gene (HBB) is screened for mutations covering about 90% of the spectrum.

METHODS

We have performed the validation of a DHPLC assay for direct genotyping of 11 known β-thalassemia mutations in the Tunisian population.

RESULTS

DHPLC assay was established based on the analysis of 62 archival β-thalassemia samples previously genotyped then validated with full concordance on 50 tests with blind randomized samples previously genotyped with DNA sequencing and with 96% of consistency on 40 samples as a prospective study.

CONCLUSION

Compared to other genotyping techniques, the DHPLC method can meet the requirements of direct genotyping of known β-thalassemia mutations in Tunisia and to be applied as a powerful tool for the genetic screening of prenatal and postnatal individuals.

A novel gap-PCR with high resolution melting analysis for the detection of α-thalassaemia Southeast Asian and Filipino β°-thalassaemia deletion

Homozygosity for the α-thalassaemia Southeast Asian (α-SEA) and Filipino β⁰-thalassaemia (β-FIL) deletions can cause serious complications leading to foetal death or life-long blood transfusions. A rapid and accurate molecular detection assay is essential in populations where the deletions are common. In this study, gap-polymerase chain reaction (PCR) with high resolution melting (HRM) analysis was developed to detect both the large deletions. Melting curves at 86.9 ± 0.1 °C were generated by normal individuals without the α-SEA deletion, 84.7 ± 0.1 °C by homozygous α-SEA deletion individuals and two melting curves at 84.7 ± 0.1 °C and 86.9 ± 0.1 °C by α-SEA deletion carriers. Normal individuals without the β-FIL deletion produce amplicons with a melting temperature (Tm) at 74.6 ± 0.1 °C, homozygous β-FIL individuals produce amplicons with Tm at 73.6 ± 0.1 °C and heterozygous β-FIL individuals generate two amplicons with Tm at 73.6 ± 0.1 °C and 74.6 ± 0.1 °C. Evaluation using blinded tests on 220 DNA samples showed 100% sensitivity and specificity. The developed assays are sensitive and specific for rapid molecular and prenatal diagnosis for the α-SEA and β-FIL deletions.

Accuracy of Reverse Dot-Blot PCR in Detection of Different β-Globin Gene Mutations

Prevention programs for β-thalassemia based on molecular diagnosis of heterozygous carriers and/or patients require the use of reliable mutation screening methods. The aim of this study was to compare between direct DNA sequencing, and reverse dot-blot PCR in detection of different β-globin gene mutations in Egyptian children with β-thalassemia. Forty children with β-thalassemia were subjected to mutation analysis, performed by both direct DNA sequencing and β-globin Strip Assay MED™ (based on reverse dot-blot PCR). The most frequent mutant alleles detected by reverse dot-blot PCR were; IVSI-110 G>A (31.25 %), IVS I-6 T > C (21.25 %), and IVS I-1 G>A (20 %). Relatively less frequent mutant alleles detected by reverse dot-blot PCR were "IVSII-1 G>A (5 %), IVSII-745 C>G (5 %), IVSII-848 C>A (2.5 %), IVSI-5 G>C (2.5 %), -87 C>G(2.5 %), and cd39 C>T (2.5 %)", While the genotypes of three patients (6 alleles 7.5 %) were not detected by reverse dot-blot PCR. Mutant alleles detected by direct DNA sequencing were the same as reverse dot-blot PCR method except it revealed the genotypes of 3 undetected patients (one patient was homozygous IVSI-110 G>A, and two patients were homozygous IVS I-1 G>A. Sensitivity of the reverse dot-blot PCR was 92.5 % when compared to direct DNA sequencing for detecting β-thalassemia mutations. Our results therefore suggest that, direct DNA sequencing may be preferred over reverse dot-blot PCR in critical diagnostic situations like genetic counseling for prenatal diagnosis.

The molecular and physiological roles of ABCC6: more than meets the eye

Abnormal mineralization occurs in the context of several common conditions, including advanced age, diabetes, hypercholesterolemia, chronic renal failure, and certain genetic conditions. Metabolic, mechanical, infectious, and inflammatory injuries promote ectopic mineralization through overlapping yet distinct molecular mechanisms of initiation and progression. The ABCC6 protein is an ATP-dependent transporter primarily found in the plasma membrane of hepatocytes. ABCC6 exports unknown substrates from the liver presumably for systemic circulation. ABCC6 deficiency is the primary cause for chronic and acute forms of ectopic mineralization described in diseases such as pseudoxanthoma elasticum (PXE), β-thalassemia, and generalized arterial calcification of infancy (GACI) in humans and dystrophic cardiac calcification (DCC) in mice. These pathologies are characterized by mineralization of cardiovascular, ocular, and dermal tissues. PXE and to an extent GACI are caused by inactivating ABCC6 mutations, whereas the mineralization associated with β-thalassemia patients derives from a liver-specific change in ABCC6 expression. DCC is an acquired phenotype resulting from cardiovascular insults (ischemic injury or hyperlipidemia) and secondary to ABCC6 insufficiency. Abcc6-deficient mice develop ectopic calcifications similar to both the human PXE and mouse DCC phenotypes. The precise molecular and cellular mechanism linking deficient hepatic ABCC6 function to distal ectopic mineral deposition is not understood and has captured the attention of many research groups. Our previously published work along with that of others show that ABCC6 influences other modulators of calcification and that it plays a much greater physiological role than originally thought.

Clinical severity of β-thalassaemia/Hb E disease is associated with differential activities of the calpain-calpastatin proteolytic system

Earlier observations in the literature suggest that proteolytic degradation of excess unmatched α-globin chains reduces their accumulation and precipitation in β-thalassaemia erythroid precursor cells and have linked this proteolytic degradation to the activity of calpain protease. The aim of this study was to correlate the activity of calpain and its inhibitor, calpastatin, with different degrees of disease severity in β-thalassaemia. CD34(+) cells were enriched from peripheral blood of healthy individuals (control group) and patients with mild and severe clinical presentations of β(0)-thalassaemia/Hb E disease. By ex vivo cultivation promoting erythroid cell differentiation for 7 days, proerythroblasts, were employed for the functional characterization of the calpain-calpastatin proteolytic system. In comparison to the control group, enzymatic activity and protein amounts of μ-calpain were found to be more than 3-fold increased in proerythroblasts from patients with mild clinical symptoms, whereas no significant difference was observed in patients with severe clinical symptoms. Furthermore, a 1.6-fold decrease of calpastatin activity and 3.2-fold accumulation of a 34 kDa calpain-mediated degradation product of calpastatin were observed in patients with mild clinical symptoms. The increased activity of calpain may be involved in the removal of excess α-globin chains contributing to a lower degree of disease severity in patients with mild clinical symptoms.

Complications of β-thalassemia intermedia in Iran during 1996-2010 (single-center study)

Patients with thalassemia intermedia (TI) experience many complications, of which the incidence varies greatly among cases. Considering the high prevalence of thalassemia in Iran, the study was carried out to determine the frequency of TI complications in Iranian patients and to find possible risk factors for each of them. Using the sampling method of "census," the authors included 153 patients who were seen in their tertiary hematology clinic with the diagnosis of TI during 1996-2010; an analytical cross-sectional study was performed and the data was analyzed by SPSS software using univariate and regression analyses. Mean age of the patients at the time of the study was 17.4 years and 36.5% were receiving transfusions (regularly or occasionally). Mean hemoglobin was 9.2 g/dL and mean serum ferritin was 858 ng/mL. Splenectomy was performed in 46.9% and it was correlated with age and the age at diagnosis in regression analysis. Cholelithiasis was found in 25.5% and was correlated with age and history of splenectomy. Pulmonary hypertension, detected in 23.5%, was correlated with thrombocytosis and mitral valve regurgitation in univariate analysis. Endocrine disease (hypogonadism, hypothyroidism, and adrenal insufficiency) was detected in 8% of the patients. In univariate analysis, endocrine disease was correlated with age of the patients. Regarding bone density of the spine, 53% of cases had osteoporosis. Thrombocytosis was present in 42% of patients and was correlated with their age. Since the severity of thalassemia intermedia vary greatly among patients, a careful evaluation of clinical, laboratory, and genetic aspects is necessary to differentiate TI in a patient at presentation. Moreover, TI patients should be carefully followed up for early detection and management of newly developed complications. The authors also suggest confirmatory controlled studies with larger sample sizes to assist in developing guidelines for surveillance and treatment of TI.

Self-reported level of and factors influencing the compliance to desferrioxamine therapy in multitransfused thalassaemias

AIM

To analyse the self-reported degree of and factors influencing the compliance to desferrioxamine (DFO) therapy in children with transfusion-dependent thalassaemia major in Malaysia.

METHODS

A cross-sectional study was conducted on all children with thalassaemia major on DFO attending Likas Hospital, Sabah, in September 2008. Patients or carer-providers were interviewed to report on the degree of compliance as either highly (administering >90% of DFO), moderately (51-90%), poorly (1%-50%) or non-compliant (0%) to DFO in the preceding month. The latest serum ferritin levels were noted.

RESULTS

The median (range) age at first blood transfusion of these 139 (73 males, median (range) age at interview: 9.0 years (2-16 years)) patients were 1.0 year (2 months to 10 years). The median (range) duration of regular DFO therapy was 2 years (2 months to 10 years). Forty-three (31%) of the patients reported themselves to be highly compliant, 70 (50%) moderately and 26 (19%) poorly or non-compliant. Multivariate analysis showed that a lower family income negatively affected the degree of compliance, while family support positively affected the degree of compliance to DFO. No correlation existed between self-reported degree of compliance and latest serum ferritin level (6444 ± µmol/L; P = 0.186).

CONCLUSION

The self-reported compliance to DFO therapy was moderate in this cohort of patients with thalassaemia major in Malaysia. The serum ferritin level was high, possibly because of the relatively short duration of DFO therapy and compliance. Oral iron chelator should be considered to improve the compliance to iron chelation.

Characterization of beta-thalassemia mutations in patients from the state of Rio Grande do Norte, Brazil

35 unrelated individuals were studied for characterization as either heterozygous or homozygous for beta-thalassemia. Molecular analysis was done by PCR/RFLP to detect the mutations most commonly associated with beta-thalassemia (β(0)IVS-I-1, β(+)IVS-I-6, and β(0)39). In the patients who showed none of these mutations, the beta-globin genes were sequenced. Of the 31 heterozygous patients, 13 (41.9%) had the β(+)IVS-I-6 mutation, 15 (48.4%) the β(0)IVS-I-1 mutation, 2 (6.5%) the β(+)IVS-I-110 mutation and 1 (3.2%) the β(+)IVS-I-5 mutation. IVS-I-6 was detected in the four homozygotes. The mutation in codon 39, often found in previous studies in Brazil, was not detected in the present case. This is the first study aiming at identifying mutations that determine beta-thalassemia in the state of Rio Grande do Norte.

A mouse model of β-thalassemia shows a liver-specific down-regulation of Abcc6 expression

β-Thalassemia and pseudoxanthoma elasticum (PXE) are distinct genetic disorders. Yet, a dystrophic mineralization phenotype similar to PXE has frequently been associated with β-thalassemia or sickle cell anemia patients of Mediterranean descent. These calcifications are clinically and structurally identical to inherited PXE. As we previously excluded the presence of PXE-causing mutations in the ABCC6 gene of β-thalassemia patients with PXE manifestations, we hypothesized that a molecular mechanism independent of gene mutations either altered the ABCC6 gene expression or disrupted the biologic properties of its product in the liver or kidneys, which are the tissues with the highest levels of expression. To test this possibility, we investigated Abcc6 synthesis in the liver and kidneys of a β-thalassemia mouse model (Hbb(th3/+)). We found a progressive liver-specific down-regulation of the Abcc6 gene expression and protein levels by quantitative PCR, Western blotting, and immunofluorescence. The levels of Abcc6 protein decreased significantly at 6 months of age and stabilized at 10 months and older ages at ∼25% of the wild-type protein levels. We studied the transcriptional regulation of the Abcc6 gene in wild-type and Hbb(th3/+) mice, and we identified the erythroid transcription factor NF-E2 as the main cause of the transcriptional down-regulation using transcription factor arrays and chromatin immunoprecipitation. The Hbb(th3/+) mice did not develop spontaneous calcification as seen in the Abcc6(-/-) mice probably because the Abcc6 protein decrease occurred late in life and was probably insufficient to promote mineralization in the Hbb(th3/+) mouse C57BL/6J genetic background. Nevertheless, our result suggested that a similar decrease of ABCC6 expression occurs in the liver of β-thalassemia patients and may be responsible for their frequent PXE-like manifestations.

Characterization of a novel deletion causing beta-thalassemia major in an Afghan family

We have identified and characterized a novel beta-globin gene deletion mutation in a family of Afghan ancestry. The proband was a 10-year-old transfusion-dependent female with the phenotype of beta-thalassemia major (beta-TM). DNA sequencing of the beta-globin gene showed no abnormalities. Multiplex ligation-dependent probe amplification (MLPA) showed reduced/absent probe height of the probe covering the 5' end of the beta-globin gene indicating a possible deletion. Gap-polymerase chain reaction (gap-PCR) produced junctional fragments and direct sequencing of the product revealed that the 5' breakpoint was 478 nucleotides upstream of the Cap site and the 3' breakpoint was in the second exon of the beta-globin gene, giving a deletion size of 909 bp. The proband was homozygous and the parents were heterozygous for the deletion. This is the first report of a large beta-thalassemia (beta-thal) deletion mutation in this ethnic group.

Comprehensive and efficient HBB mutation analysis for detection of beta-hemoglobinopathies in a pan-ethnic population

Current methods that assay hemoglobin beta-globin chain variants can have limited clinical sensitivity when applied techniques identify only a predefined panel of mutations. Even sequence-based assays may be limited depending on which gene regions are investigated. We sought to develop a clinically practical yet inclusive molecular assay to identify beta-globin mutations in multicultural populations. We highlight the beta-globin mutation detection assay (beta-GMDA), an extensive gene sequencing assay. The polymerase chain reaction (PCR) primers are located to encompass virtually all hemoglobin beta locus (HBB) mutations. In addition, this assay is able to detect, by gap PCR, a common large deletion (Delta619 base pair), which would be missed by sequencing alone. We describe our 5-year experience with the beta-GMDA and indicate its capability for detecting homozygous, heterozygous, and compound heterozygous sequence changes, including previously unknown HBB variants. The beta-GMDA offers superior sensitivity and ease of use with comprehensive detection of HBB mutations that result in beta-globin chain variants.

Rapid identification of HBB gene mutations by high-resolution melting analysis

OBJECTIVE

This study was undertaken to identify HBB gene mutation.

DESIGN AND METHODS

Herein we evaluated high-resolution melting analysis in the identification of HBB mutations.

RESULTS

We have successfully established a diagnostic strategy for identifying HBB gene mutations including c.-78A>G, c.-79A>G, c.2T>G, c.79_80insT, c.84_85insC, c.123_124insT, c.125_128delTCTT, c.130 G>T, c.170G>A, c.216_217ins A and c.316-197 C>T from wild-type DNA using HRM analysis. The results of HRM analysis were confirmed by direct DNA sequencing.

CONCLUSIONS

In summary, we report that HRM analysis is an appealing technique for the identification of HBB mutations. We also believe that HRM can be used as a method for prenatal diagnosis of beta-thalassemia.

A Novel β-Thalassemic Allele Due to a Two Nucleotide Deletion: β76 (−GC)

We have identified and characterized a novel beta-thalassemic mutation in a North African adult. The molecular defect consists of a two nucleotide (nt) deletion in the beta-globin gene at codon 76 [beta76 (-GC), c.229-230delGC]. This frameshift mutation generates a TGA stop codon at position 89. The carrier presented with mild microcytic anemia (Hb 12.8 g/dL, MCV 60 fL), no detectable Hb F, an elevated Hb A2 level (5.5%) with no other mutation in the beta-globin gene and none of the more common known deletions in the alpha-globin cluster. No abnormal hemoglobin (Hb) was present in routine electrophoresis or in high performance liquid chromatography (HPLC) analyses. Pathologic inclusions were absent in both mature red cells and in reticulocytes. This observation reinforces the hypothesis that nonsense and frameshift mutations that result in a premature stop codon in exon 1 or exon 2 inherited in the heterozygous state do not generate dominant beta-thalassemia (thal). This is the first example of a premature stop codon at position 89.

β-Thalassemia Due to a Novel Nonsense Mutation at Codon 37 (TGG→TAG) Found in an Afghanistani Family

We have identified and characterized a novel beta-thalassemic mutation in an Afghanistanifamily. The molecular pathology consists of a single base substitution (TGG-->TAG) at codon 37 of the beta-globin gene, giving rise to a stop codon (TAG). Premature stop of translation results in a truncated protein and usually the phenotype of beta-thalassemia (thal) major in homozygous individuals. However, this was not the case in our proband, who was homozygous for the codon 37 mutation. He presented with the phenotype of thalassemia intermedia with a hemoglobin (Hb) level of 8.1 g/dL and no previous history of blood transfusions. High performance liquid chromatography (HPLC) analysis showed exclusively Hb F except for a Hb A2 level within normal limits. Subsequent analysis demonstrated homozygosity for the XmnI Ggamma polymorphism and heterozygosity for a deletional alpha-thal (alphaalpha/-alpha(-3.7)). These findings might, at least partly, explain the beta-thal intermedia phenotype observed in the proband.

Prevalence of endocrinopathies in patients with Beta-thalassaemia major - a cross-sectional study in oman

BACKGROUND

Beta-thalassaemia major is a common medical problem worldwide. There is little data dealing with the nature and prevalence of different endocrine disorders in this disease in the Sultanate of Oman.

OBJECTIVES

To establish the prevalence and times of occurrence of endocrine disorders in patients with beta-thalassaemia major.

METHODS

This cross-sectional study was conducted during Jan-Jul 2008 and dealt with 30 Omani patients with transfusion-dependent homozygous beta-thalassaemia major who were consulting Thalassaemia Clinic, Royal Hospital. They included 15 males and 15 females, aged 16 to 32 years with median of 21 years and mean ± SD of 21.23 ± 3.42 years. The medical records of these patients were reviewed and their endocrine functions were assessed. This assessment included pituitary and gonadal function, thyroid function, bone profile (including Parathyroid Hormone), morning cortisol and fasting glucose. These profiles were reviewed to exclude hypogonadism, hypothyroidism, hypoparathyroidism, hypoadrenalism or diabetes mellitus.

RESULTS

Hypogonadism was reported in 22 (73.3%) patients (13 female, 9 male). Low levels of Follicle-Stimulating Hormone (FSH) and low Luteinizing Hormone (LH) with low estradiol (in females) or testosterone (in males) was noted in 15 (50.0%) patients (7 female, 8 male). Normal (but inappropriately low) levels of FSH and LH with low estradiol (in females) or testosterone (in males) was noted in 7 (23.3%) patients (6 female, 1 male). Primary hypothyroidism was present in only 1 (3.3%) patient (female) who Hypoparathyroidism was found in 3 (10.0%) patients (2 female, 1 male). Diabetes mellitus with high fasting glucose was noted in 8 (26.7%) patients (2 female, 6 male). Morning cortisol levels for all patients were within the reference range with no suspicion of hypoadrenal cortical function. Eight (26.7%) patients had no endocrine disorder, 12 (40.0%) patients had one disorder, 8 (26.7%) patients had 2 disorders, and 2 (6.7%) patients had 3 endocrine disorders. There was no significant difference (p>0.050) in mean serum ferritin in thalassaemics with or without endocrinopathy, regardless of the number of endocrinopathy.

CONCLUSION

There is high prevalence of endocrine disorders among Omani beta-thalassaemic adult patients. This signifies the importance of awareness for their development and monitoring for early detection and replacement therapy. No relationship between serum ferritin and development of endocrinopathy was noted.

Carrier Testing for Autosomal- Recessive Disorders

The aim of carrier testing is to identify carrier couples at risk of having offspring with a serious genetic (autosomal recessive) disorder. Carrier couples are offered genetic consultation where their reproductive options, including prenatal diagnosis, are explained. The Ashkenazi Jewish population is at increased risk for several recessively inherited disorders (Tay-Sachs disease, Cystic fibrosis, Canavan disease, Gaucher disease, Familial Dysautonomia, Niemann-Pick disease, Fanconi anemia, and Bloom syndrome). Unlike Tay-Sachs disease, there is no simple biochemical or enzymatic test to detect carriers for these other disorders. However, with the rapid identification of disease-causing genes in recent years, DNA-based assays are increasingly available for carrier detection. Approximately 5% of the world's population carries a mutation affecting the globin chains of the hemoglobin molecule. Among the most common of these disorders are the thalassemias. The global birth rate of affected infants is at least 2 per 1000 (in unscreened populations), with the greatest incidence in Southeast Asian, Indian, Mediterranean, and Middle Eastern ethnic groups. Carriers are detected by evaluation of red cell indices and morphology, followed by more sophisticated hematological testing and molecular analyses. The following issues need to be considered in the development of a carrier screening program: (1) test selection based on disease severity and test accuracy; (2) funding for testing and genetic counselling; (3) definition of the target population to be screened; (4) development of a public and professional education program; (5) informed consent for screening; and (6) awareness of community needs.

The thalassaemia syndromes

The thalassaemia syndromes, endemic in the Mediterranean area, the Middle East, the Indian subcontinent, the Far East and in tropical Africa, are the most common hereditary disorders in humans, and millions of people are affected by diseases. Due to a widespread population flow between continents in recent past centuries, the thalassaemias are now occurring with relatively high frequency in many non-endemic areas. In the Nordic countries, homozygous thalassaemia is still relatively rare, and most health-care personnel are not familiar with these diseases. This article focuses on two important issues, namely the biological and the clinical aspects of thalassaemia.

Characterisation and confirmation of rare beta-thalassaemia mutations in the Malay, Chinese and Indian ethnic groups in Malaysia

AIMS

In Malaysia, about 4.5% of the Malay and Chinese populations are heterozygous carriers of beta-thalassaemia. The initial identification of rare beta-globin gene mutations by genomic sequencing will allow the development of simpler and cost-effective PCR-based techniques to complement the existing amplification refractory mutation system (ARMS) and gap-PCR used for the identification of beta-thalassaemia mutations.

METHODS

DNA from 173 beta-thalassaemia carriers and five beta-thalassaemia major patients from the Malay, Chinese and Indian ethnic groups were first analysed by ARMS and gap-PCR. Ninety-five per cent (174/183) of the 183 beta-globin genes studied were characterised using these two techiques. The remaining nine uncharacterised beta-globin genes (4.9%) were analysed using genomic sequencing of a 904 bp amplified PCR product consisting of the promoter region, exon 1, intervening sequence (IVS) 1, exon 2 and the 5' IVS2 regions of the beta-globin gene.

RESULTS

The rare beta-globin mutations detected in the Chinese patients were CD27/28 (+C) and CD43 (GAG-TAG), and -88 (C-T) in an Indian patient. Beta-globin mutations at CD16 (-C), IVS1-1 (G-A), IVS2-1 (G-A), -86 (C-G) and Haemoglobin South Florida (CD1, GTG-ATG) were confirmed in the Malay patients.

CONCLUSIONS

The seven rare beta-globin mutations and a rare haemoglobin variant confirmed in this study have been described in other populations but have not been previously described in Malaysian beta-thalassemia patients.

Nine unknown rearrangements in 16p13.3 and 11p15.4 causing alpha- and beta-thalassaemia characterised by high resolution multiplex ligation-dependent probe amplification

BACKGROUND

Approximately 80% of the alpha- and 10% of the beta-thalassaemias are caused by genomic deletions involving the alpha- and beta-globin gene clusters on chromosomes 16p13.3 and 11p15.5, respectively. Gap-PCR, Southern blot analysis, and fluorescent in situ hybridisation are commonly used to identify these deletions; however, many deletions go undetected using conventional techniques.

METHODS

Patient samples for which no abnormalities had been found using conventional DNA techniques were analysed by a three colour multiplex ligation-dependent probe amplification assay. Two sets of 35 and 50 probes, covering a region of 700 kb of the alpha- and 500 kb of the beta-globin gene cluster, respectively, were designed to detect rearrangements in the alpha- and beta-globin gene clusters.

RESULTS

In 19 out of 38 patient samples, we found 11 different alpha-thalassaemia deletions, six of which were not previously described. Two novel deletions leaving the alpha-globin gene cluster intact were found to cause a complete downregulation of the downstream alpha-genes. Similarly, 31 out of 51 patient samples were found to carry 10 different deletions involving the beta-globin gene cluster, three of which were not previously described. One involves the deletion of the locus control region leaving the beta-globin gene cluster intact.

CONCLUSIONS

These deletions, which are not easily detected by conventional techniques, may have clinical implications during pregnancy ranging from mild to life threatening microcytic haemolytic anaemia in neonates. The approach as described here is a rapid and sensitive method for high resolution analysis of the globin gene clusters and for any region of the genome.

Mutations associated with beta-thalassemia intermedia in Kuwait

OBJECTIVE

To identify the beta-globin gene mutations associated with beta-thalassemia (beta-thal) intermedia in Kuwait.

SUBJECTS AND METHODS

Eighteen patients from 13 unrelated families, mean age 12.7 +/- 8.1 years, range 4-31 years, were involved in the study. They did not require regular blood transfusion. Complete blood count and cation exchange high-performance liquid chromatography hemoglobin quantitation were carried out using standard techniques. Beta-thal mutations were identified with a combination of PCR amplification, allele- specific oligonucleotide hybridization or direct DNA sequencing. The patients were also screened for the alpha2-globin gene (-3.7 kb) deletion.

RESULTS

Of the 13 families, 4 were homozygous for the IVS-I-II (G-->A) and 4 for the IVS-I-6 (T-->C) mutations, while 1 each was a compound heterozygote for the following mutation combinations: CD 8 (-AA) and -101 (C-->T); IVS-I-6 (T-->C) and CD 19 (A-->G); IVS-II-1 (G-->A) and -28 (A-->C); IVS-I-110 (G-->A) and deltabeta0 deletion. Therefore, homozygosity for two typically mild mutations (IVS-II-1 and IVS-I-6) accounted for 61% of the genotypes in our patients.

CONCLUSION

Our results indicate that screening should commence with these two common alleles in Kuwaiti patients presenting with beta-thal syndrome. Early identification of intermedia patients will avoid the complications following an unnecessary hypertransfusion program.

β-Globin mutation detection by tagged single-base extension and hybridization to universal glass and flow-through microarrays

To test the feasibility of developing a diagnostic microarray for a specific disease, we selected all pathogenic changes of the beta-globin gene occurring at a frequency >/=1% in the multi-ethnic Dutch population for analysis. A tagged single-base extension (SBE) approach was used to detect 19 different mutations causing beta-thalassemia or abnormal hemoglobins. In the SBE reaction, the primers were elongated at the 3'site with a fluorescently labeled dideoxyribonucleotide triphosphate (ddNTP) complementary to the mutation, following tag hybridization to a glass or flow-through microarray. We compared the performance of a generic glass array and a porous system, by testing each mutation separately using heterozygous carriers and by screening a cohort of 40 unknown beta-thalassemia carriers and patients. The results were verified by direct sequencing. The microarray system was able to detect 17 beta-globin mutations simultaneously with >95% accuracy in a single SBE reaction. The flow-through array performed slightly better (96%), but the main advantages of the system included real-time data recording and a considerable time saving achieved through a reduced hybridization time.

Screening and genetic diagnosis of haemoglobin disorders

The inherited haemoglobinopathies are large group of disorders that include the thalassaemias and sickle cell disease. Carrier detection methods must be able to detect alpha-, beta- and deltabeta-thalassaemias, HPFH disorders and haemoglobin variants. Carrier diagnosis involves the accurate measurement of MCH, MCV, Hb A(2) and Hb F values in combination with an understanding of the haematological characteristics of the different types of thalassaemia genes and their interactions. The majority of the common thalassaemia mutations and abnormal haemoglobins can be identified by PCR-based techniques. The main applications of molecular analysis for carrier diagnosis are: the analysis of alpha-thalassaemia mutations by gap-PCR to discriminate between heterozygous alpha-thalassaemia and homozygous alpha-thalassaemia; the identification of beta-thalassaemia mutations for patients requiring prenatal diagnosis and for the prediction of the severity of the clinical phenotype of homozygous beta-thalassaemia; to discriminate between deltabeta-thalassaemia and HPFH deletions by gap-PCR.

Thalassemia: current approach to an old disease

This article discusses the approach for recognition, diagnosis, and management of the thalassemias, and reviews new prospects of therapy, focusing mostly on the beta-thalassemias--the more severe and clinically important type, beta-thalassemia major is typically treated with regular transfusion and chelation therapy. New strategies for specific therapy including monitoring of iron induced organ damage, fetal hemoglobin augmentation as an alternative for transfusions, bone marrow transplantation offer hope for prevention of complications and better care of the beta-thalassemias.

Rapid detection of the major Mediterranean beta-thalassaemia mutations by real-time polymerase chain reaction using fluorophore-labelled hybridization probes

We present a new method to detect the major beta-thalassaemia mutations of the Mediterranean countries (IVS I-1, IVS I-6, IVS I-110, CD-37 and CD-39). The procedure is based upon real-time polymerase chain reaction (PCR), using specific fluorescently labelled hybridization probes. The melting curves for each of the specific probes obtained after PCR enabled the identification of different alleles. Genotyping of 71 patients with thalassaemia and 20 controls without thalassaemia by the established method and conventional allele-specific restriction enzyme analysis produced identical results. The established method is a robust, fast and straightforward assay that allows detection of the major Mediterranean beta-thalassaemia mutations simultaneously in less than 60 min.

Beta-thalassemia in the Korean population

Beta-thalassemia is uncommon in the Korean population, however it must be considered in the differential diagnosis of hypochromic anemia. The molecular characterization of beta-thalassemia is absolutely necessary for molecular diagnosis as well as any genetic epidemiological study in this region. We analyzed the molecular basis of beta-thalassemia in 47 Korean families. Using direct sequencing of genomic DNA amplified through PCR and haplotype analysis, 44 beta-thalassemia genes were characterized, all of which were heterozygous. Fourteen different mutations were identified. The common mutations noted included the initiation codon (CD) ATG-->AGG (23.4%), CD 17 A-->T (21.2%), and IVS-II-1 G-->A (12.7%). Interestingly, mutations causing dominantly inherited beta-thalassemia were common (17.0%). All cases of IVS-II-1 G-->A mutations were linked to the silent mutation of CD 91 C-->T of the -globin gene. The initiation CD ATG-->AGG and IVS-II-1 G-->A with CD 91 C-->T were found in the Far East only, and may be inherited from a common origin for each mutation, at least in Koreans. CD17 A-->T and CDs 41/42-TTCT were suggested to be introduced by gene-flow from southern China. Otherwise, Hb Korea, CDs 89/90 -GT and a novel beta-thalassemia mutation, CD 131 CAG-->TAG, were only identified in Koreans. This mutation spectrum is characteristic of the low prevalent area of beta-thalassemia, however it is quite different even from the adjacent countries, Japan or China.

Model mice for Presbyterian hemoglobinopathy (Asn(beta108)-->Lys) confer hemolytic anemia with altered oxygen affinity and instability of Hb

Hb Presbyterian is a variant hemoglobin that carries Lys at Asn-108 of beta-globin. This variant Lys(beta108) residue enhances the stability of Hb in the deoxy-state, conferring the low affinity for oxygen-binding in vitro. In the present study, we generated mutant mice carrying the Presbyterian mutation (Asn(beta108)-->Lys) at the beta-globin locus by a targeted knock-in strategy. Heterozygous mice showed the expression of Hb Presbyterian in 27.7% of total peripheral blood without any hematological abnormalities, which well mimicked human cases. On the other hand, homozygous mice exclusively expressed Hb Presbyterian in 100% of peripheral blood associated with hemolytic anemia, Heinz body formation, and splenomegaly. Hb Presbyterian showed instability in an in vitro precipitation assay. Erythrocytes from homozygous mice showed a shortened life span when transfused into wild-type mice, confirming that the knocked-in mutation of Lys(beta108) caused hemolysis in homozygous mice. This is the first report on the hemolytic anemia of unstable hemoglobin in an animal model. These results confirm the notion that the higher ratio of an unstable variant beta-globin chain in erythrocytes triggers the pathological precipitation and induces hemolysis in abnormal hemoglobinopathies.

Molecular spectrum of beta-thalassemia in the Iranian Province of Hormozgan

Prevention of beta-thalassemia implies knowledge of the molecular spectrum occurring in the population at risk. This knowledge is necessary, especially when a prevention protocol is applied to a multiethnic population. For this purpose, we have recently analyzed a large population of Iranian patients living in the Province of Hormozgan in Iran, and a small group of Iranian patients living in The Netherlands. We have found a different mutation spectrum in both populations as compared to the data obtained by other authors for the Iranian regions of Tehran, Fars, Sistan Balouchestan, Bushehr, and Khouzestan. The IVS-I-5 (G-->C) is the most frequent mutant in the province of Hormozgan (69%), followed by the IVS-II-1 (G-->A) (9.6%), while the IVS-I-1 (G-->A) was the most frequent defect found in the Iranian population sample in The Netherlands. The IVS-II-745 (C-->G) mutation in cis with the 5'UTR (untranslated region) +20 (C-->T) transition was observed in two unrelated, transfusion-dependent homozygotes, living in the Hormozgan Province where, in contrast with populations living in other provinces of Iran, no IVS-I-110 (G-->A) or IVS-I-1 (G-->A) mutations were found. We report the molecular spectra of our population samples and compare them with the mutation spectra observed in the Iranian populations by other authors. We discuss the severe phenotype of the patients homozygous for the IVS-II-745 (C-->G) mutation, linked in cis to the 5'UTR +20 (C-->T) transition. Molecular analysis using commercial kits is briefly compared with denaturing gradient gel electrophoresis, emphasizing the value of a rapid method of detection for molecular defects in areas where many mutations occur.

An in vitro system for expression analysis of mutations of the beta-globin gene: validation and application to two mutations in the 5' UTR

We describe the setting up of an in vitro expression system for the analysis of mutations of the beta-globin gene. The system is based on the stable transfection of a normal or mutated beta-globin gene into mouse erythroleukaemia (MEL) cells. The expression construct contains an Agamma gene as an internal control and both globin genes are under the control of the HS2 element of the beta LCR. The system enables analysis of transcription, RNA processing and transport, as well as mRNA stability. With non-mutant genes, high-level expression of both beta and Agamma genes is seen and both mRNAs are stable. The system was validated by comparing the expression of the beta654 thalassaemia splicing mutation in MEL cells with its well-characterized expression in vivo. The level of the initial transcript, the proportion of abnormally spliced mRNA and its instability during erythroid cell maturation were all faithfully reproduced. The system was used to examine the mechanism by which two mutations in the beta-globin 5' untranslated region (5' UTR) result in beta thalassaemia. Surprisingly, the mechanism appeared to differ in the two cases, with the C-G substitution at position +33 affecting transcription, whereas the -T deletion at position +10 resulted in a translational defect. The stably transfected MEL cells, with an internal control and an endogenous enhancer, appear to be a valid and realistic experimental model, superior to transient expression studies. This system should find wide application in the analysis of the effects and mechanisms of gene inactivation in mutations affecting the beta-globin as well as other genes.