Mutational spectrum of HBD gene in the Chinese population: Description of 36 mutations including 11 novel variants.

INTRODUCTION: Mutations in the hemoglobin subunit delta (HBD) gene (MIM#142000) are associated with decreased levels of the Hemoglobin A2 (Hb A2 ) fraction. We aimed to examine the prevalence of HBD gene mutations and summarize their characteristics in the Chinese population. METHODS: Individuals who exhibited Hb A2 levels below 1.8%, with or without Hb A2 variant peaks, were chosen for further investigation. Hemoglobin analysis was conducted using capillary electrophoresis. Common α and ß-thalassemia in China were detected using gap-PCR and reverse dot blot hybridization. The presence of HBD gene mutations was confirmed by DNA sequencing. RESULTS: A total of 188 patients were identified as carriers of the HBD gene mutation, with a prevalence of approximately 0.46%. We discovered 36 types of mutations, 30 of which resulted in δ-globin variants, while the remaining 6 resulted in δ-thalassemia. The most common mutation was HBD:c.-127 T > C, accounting for 87.2% of δ-thalassemia cases. In addition, we identified 11 novel HBD gene mutations and found 10 cases compounded with other common thalassemias. CONCLUSION: We observed a high prevalence of HBD gene mutations in southern China. Our findings provide a genetic basis for screening for δ-thalassemia and enrich the spectrum of HBD gene mutations.

First report of the spectrum of δ-globin gene mutations among women of reproductive age in Fujian area-Discrimination of δ-thalassemia, α-thalassemia, and Iron Deficiency Anemia.

BACKGROUND: Low HbA2 level is an underlying of δ-thalassemia, α-thalassemia, and IDA. Interactions of these disorders can generate a wide spectrum of phenotype, which will pose diagnostic conundrum for clinical assessment, carrier screening, and genetic counseling. METHODS: Subjects with HbA2 levels below 2.0% with normal or reduced hematological parameters were recruited for further investigation. δ-globin gene mutations were identified by DNA sequencing of the HBD gene. Serum ferritin (SF) concentration was determined by the chemiluminescent microparticle immunoassay. The three common deletional α-thalassemia (--SEA /αα, -α3.7 /αα, and -α4.2 /αα) were detected using Gap-PCR, detection of the point mutations in the three nondeletional α-thalassemia (αCS α/αα,αQS α/αα,αWS α/αα), and the 17 common ß-thalassemia was performed using reverse dot blot hybridization (RDB). RESULTS: We had characterized the δ-globin gene mutations in 20 cases, revealing a frequency of 0.4% in the women of reproductive age (20/4 792). Two previously known mutations:-77 T > C and -30 T > C and 3 novel δ-globin gene defects: -44G > A,CD87C > T, and CD134T > A were found. In the selected cases, we also found 85 cases confirmed with (51.2%,85/166) IDA and 39 cases (23.5%,39/166) with common α-thalassemia. Subjects with δ-thalassemia had statistically higher levels of Hb, MCV, and MCH compared with other two groups, whereas statistically lower levels of RDW were seen in δ-thalassemia group. What's more, statistically higher levels of SF were seen in δ-thalassemia group, compared with IDA groups. CONCLUSION: We reported the spectrum of δ-thalassemia mutations for the first time with the frequency of 0.4% among women of reproductive age in Fujian area and found that -77T > C mutation was the most common mutation, followed by -30T > C mutation. What's more, 3 novel δ-globin gene defects: -44G > A,CD87C > T and CD134T > A were found. A thorough analysis of the hematological, electrophoretic characterization, and the level of SF was needed to suspect and further investigate the existence of IDA, α-thalassemia, and δ-thalassemia.

Genotypic-phenotypic heterogeneity of 뫧-thalassemia and hereditary persistence of fetal hemoglobin (HPFH) in India.

Large deletions in the ß-globin gene cluster lead to increased HbF levels by delaying the γ- to ß-globin switch process. However, these deletions when inherited as a homozygous condition or when co-inherited with ß-thalassemia result in variable clinical phenotypes. Individuals or families with a clinically presenting child, where the parents had HbF levels ≥ 10%, were further screened for the presence of large ß-globin cluster deletions. Six deletions in the ß-globin gene cluster were screened by GAP-PCR, and the uncharacterized deletions were further analyzed by gene dosage or by multiplex ligation-dependent probe amplification (MLPA). Among 192 individuals suspected for the inheritance of large deletions, 138 were heterozygous for large deletions, 45 were compound heterozygous of a large ß-globin cluster deletion and ß-thalassemia, and 9 were found to be homozygous for deletions. Among the heterozygotes, the Asian Indian inversion-deletion was found to be the most common deletion (39.9%), followed by the HPFH-3 deletion (30.0%). Other deletions 49.3 kb, δß-thalassemia (21.2%), and 32.6 kb deletion (4.4%) were also found to be prevalent in our population. Patients compound heterozygous or homozygous for HPFH-3 and 32.6 kb deletions showed a milder clinical presentation, as compared with the patients compound heterozygous or homozygous for the Asian Indian inversion-deletion and 49.3 kb δß-thalassemia. This comprehensive study highlights the mutation spectrum of large ß-globin cluster deletions and the clinical heterogeneity in the patients homozygous or compound heterozygous with ß-thalassemia, thus asserting the need for molecular characterization of these deletions.

Molecular epidemiology and hematologic characterization of 뫧-thalassemia and hereditary persistence of fetal hemoglobin in 125,661 families of greater Guangzhou area, the metropolis of southern China.

BACKGROUND: Individuals with δß-thalassemia/HPFH and ß-thalassemia usually present with intermedia or thalassemia major. No large-scale survey on HPFH/δß-thalassemia in southern China has been reported to date. The purpose of this study was to examine the molecular epidemiology and hematologic characteristics of these disorders in Guangzhou, the largest city in Southern China, to offer advice for thalassemia screening programs and genetic counseling. METHODS: A total of 125,661 couples participated in pregestational thalassemia screening. 654 subjects with fetal hemoglobin (HbF) level ≥ 5% were selected for further investigation. Gap-PCR combined with Multiplex ligation dependent probe amplification (MLPA) was used to screen for ß-globin gene cluster deletions. Gene sequencing for the promoter region of HBG1 /HBG2 gene was performed for all those subjects. RESULTS: A total of 654 individuals had hemoglobin (HbF) levels≥5, and 0.12% of the couples were found to be heterozygous for HPFH/δß-thalassemia, including Chinese Gγ (Aγδß)0-thal, Southeast Asia HPFH (SEA-HPFH), Taiwanese deletion and Hb Lepore-Boston-Washington. The highest prevalence was observed in the Huadu district and the lowest in the Nansha district. Three cases were identified as carrying ß-globin gene cluster deletions, which had not been previously reported. Two at-risk couples (0.0015%) were required to receive prenatal diagnosis. We also found 55cases of nondeletional-HPFH (nd-HPFH), including 54 with Italian nd-HPFH and one with the Aγ-197C-T heterozygous state. It is difficult to discriminate between Chinese Gγ (Aγδß)0-thal and Italian nd-HPFH carriers using hemoglobin (Hb) analysis. CONCLUSIONS: This study is the first to describe the familial prevalence of HPFH/δß-thalassemia and the high-risk rate in Greater Guangzhou Area, and the findings will support the implementation of thalassemia screening for three common deletions by gap-PCR. We also presented a systematic description of genotype-phenotype relationships which will be useful for genetic counseling and prenatal diagnostic services for ß-thalassemia intermedia.

Analysis of deletional hereditary persistence of fetal hemoglobin/δß-thalassemia and δ-globin gene mutations in Southerwestern China.

BACKGROUND: Deletional hereditary persistence of fetal hemoglobin (HPFH)/δß-thalassemia and δ-thalassemia are rare inherited disorders which may complicate the diagnosis of ß-thalassemia. The aim of this study was to reveal the frequency of these two disorders in Southwestern China. METHODS: A total of 33,596 subjects were enrolled for deletional HPFH/δß-thalassemia, and positive individuals with high fetal hemoglobin (Hb F) level were diagnosed by multiplex ligation-dependent probe amplification (MLPA). A total of 17,834 subjects were analyzed for mutations in the δ-globin gene. Positive samples with low Hb A2 levels were confirmed by δ-globin gene sequencing. Furthermore, the pathogenicity and construction of a selected δ-globin mutation were analyzed. RESULTS: A total of 92 suspected cases with Hb F ≥5.0% were further characterized by MLPA. Eight different deletional HPFH/δß-thalassemia were observed at a frequency of 0.024%. In addition, 195 cases suspected to have a δ-globin gene mutation (Hb A2 ≤2.0%) were characterized by molecular analysis. δ-Globin gene mutation was found at a frequency of 0.49% in Yunnan. The pathogenicity and construction for a selected δ-globin mutation was predicted. CONCLUSION: Screening of these two disorders was analyzed in Southwestern China, which could define the molecular basis of these conditions in this population.

Contrasting co-inheritance of alpha and beta mutations in delta beta thalassemia and hereditary persistence of fetal hemoglobin: a study from India.

BACKGROUND AND OBJECTIVES: Coinheritance of 뫧 thalassemia and HPFH with inherited factors is sparsely documented and may affect treatment modalities. So, we screened the presence of α deletion and ß mutations in 뫧 thalassemia and HPFH disorders in 52 cases with high Hb F concentration. MATERIAL AND METHODS: Fifty-two individuals with raised HbF levels were study subjects. CZE was done for quantitative assessment of hemoglobin variants. Asian Indian inversion deletion break point type A, B and HPFH-3 were done by GAP-PCR. RESULTS: 18/52 cases of 뫧 Gγ (Aγδß)0 thalassemia and 28/52 cases of HPFH-3 deletion were characterized. 6/52 patients with raised HbF levels were negative for 뫧 Gγ (Aγδß)0 and HPFH-3 deletion. 9/18 (50%) were heterozygous for Gγ(Aγδß)0 break point type A, 6/18 (33%) were heterozygous for break point type B and 3/18 (17%) were homozygous. Of the nine patients heterozygous for Gγ(Aγδß)0 break point type A, three (33%) patients were double heterozygous with alpha 3.7 kb deletion and two (22%) patients showed compound heterozygosity with IVS 1-5(G-C) mutation. 4/9 (45%) patients were Gγ(Aγδß)0 heterozygous. DISCUSSION AND CONCLUSION: We found 5/18(27.ß) δß-thalassemia cases with co-inherited alpha 3.7 deletion and 3/18 (16ß) cases with IVS 1-5(G-C) mutation. Patients showed features of thalassemia intermedia phenotype among which those with co-inherited IVS 1-5(G-C) mutation showed severe phenotype as compared to those with co-inherited alpha 3.7 deletion. So, we highlight importance of genotyping of patients with 뫧 thalassemia or HPFH and coinheritance with inherited factors which plays crucial role in clinicopathological profile and setting up prenatal diagnostic protocol.

The prevalence and molecular characterization of (뫧)0 -thalassemia and hereditary persistence of fetal hemoglobin in the Chinese Zhuang population.

OBJECTIVE: To reveal the prevalence and molecular characterization of (δß)0 -thalassemia [(δß)0 -thal] and hereditary persistence of fetal hemoglobin (HPFH) in the Chinese Zhuang population. METHODS: A total of 105 subjects with fetal hemoglobin (Hb F) level ≥5% from 14 204 unrelated ones were selected for the study. Multiplex ligation dependent probe amplification was firstly used to analyze dosage changes of the ß-globin gene cluster for associated with (δß)0 -thal and HPFH mutations. The gap polymerase chain reaction was then performed to identify the deletions using the respective flanking primers. Hematologic data were recorded and correlated with the molecular findings. RESULTS: Twenty-one (0.15%) subjects were diagnosed with Chinese G γ(A γδß)0 -thal. Nine (0.06%) were diagnosed with Southeast Asia HPFH (SEA-HPFH) deletion. Seventy-five (0.53%) cases remained uncharacterized. Three genotypes for Chinese G γ(A γδß)0 -thal and SEA-HPFH deletion were identified, respectively. The genotype-phenotype relationships were discussed. CONCLUSION: Our study for the first time demonstrated that (δß)0 and HPFH were not rare events, and molecular characterized G γ(A γδß)0 -thal and HFPH mutations in the Chinese Zhuang population. The findings in our study will be useful in genetic counseling and prenatal diagnostic service of ß-thalassemia in this populations.

Hb A1c Determination by Capillary Electrophoresis is an Efficient Method for Detecting ß-Thalassemias and Hemoglobin Variants.

Glycated hemoglobin (Hb A1c) determination by multicapillary zone electrophoresis (MZE) can additionally be used to detect Hb A2, Hb F and most common hemoglobin (Hb) variants. We assessed the effectiveness of this method for detecting ß-thalassemia (ß-thal), δß-thalassemia (δß-thal) and most common Hb variants. Moreover, Hb F/Hb A2 is evaluated as an index for discriminating between ß- and δß-thal traits. The theoretical ß-thalassemia major (ß-TM) birth rate in our healthcare area is calculated and contrasted with real data. A MZE technique was used for Hb A1c measurements in 27,724 patients. Previous criteria for carrier detection were established and subsequently confirmed by molecular biology techniques. Positive predictive value (PPV) was 100.0%. The prevalence of ß-thal trait (including δß-thal) was 0.34%. The most prevalent mutations (estimated per 100,000 population) were HBB: c.118C > T (57.7%), HBB: c.93-21G>A (50.5%), HBB: c.92 + 1G > A (43.3%), HBB: c.92 + 6T > C (32.5%) and HBB: c.20delA (18.0%) for ß-thalassemias, and Hb S (HBB: c.20A > T) (32.5%) and Hb J-Baltimore (HBB:c.3880T>A) (28.9%) for Hb variants. We found a paradoxical result between the theoretical ß-TM birth rate and real data. We calculated an optimal Hb F/Hb A2 index cutoff of 0.71 for discriminating between ß- and δß-thal traits. This method is highly cost-effective for detecting ß-thalassemias and common Hb variants. Prevalence results match previous data for the Spanish population. Heterogeneity of mutations in Spain has markedly increased as a consequence of migration. The Hb F/Hb A2 index cutoff could be used to predict δß-thal trait.

Molecular Characterization of δ-Thalassemia in Iran.

δ-Thalassemia (δ-thal) (OMIM #142000) resulting from mutations on the HBD gene usually has no clinical consequences. However, it may cause the misdiagnosis of ß-thalassemia (ß-thal) carriers by lowering the Hb A2 level to the normal range. Therefore, a study for δ-thal should be considered as a step in the detection of at-risk couple in our region. The aim of the present study was to characterize the mutations of the HBD gene in ß-thal carriers with normal Hb A2 levels, and also in normal individuals with Hb A2 of less than 2.0%. Four ß-thal carriers with normal Hb A2 and 39 individuals with Hb A2 of less than 2.0% were enrolled. Genomic DNA was extracted by the salting out method and the HBD gene was investigated by polymerase chain reaction (PCR) and direct DNA sequencing. Hb A2-Yialousa (HBD: c.82 G > T) was the most common variant found in the HBD gene, but the following mutations were also found: Hb A2-NYU (HBD: c.39 T > A), Hb A2-Coburg (HBD: c.350 G > A), Hb A2-Etolia (HBD: c.257 T > C), Hb A2-Fitzroy (HBD: c.428 C > A) and the δ-IVS-I-5 (G > T) (HBD: c.92 + 5 G > T). One case was a compound heterozygote for δ-IVS-I-5/Hb A2-Fitzroy. The results of this single center study suggest that the mutations in the HBD gene in the Iranian population are heterogeneous and should be considered in genetic counseling of families.

A study of δ-globin gene mutations in the UK population: identification of three novel variants and development of a novel DNA test for Hb A'2.

We report here the spectrum of δ-globin gene mutations found in the UK population. Nine different δ chain variants and two δ-thalassemia (δ-thal) mutations were characterized in a study of 127 alleles in patients with either a low Hb A2 value or a split Hb A2 peak on high performance liquid chromatography (HPLC). The most common δ chain variant was Hb [Formula: see text] (or Hb B2) [δ16(A13)Gly → Arg; HBD: c.49G > C] (77.0%), followed by Hb A2-Yialousa [δ27(B9)Ala → Ser; HBD: c.82G > T] (12.0%), Hb A2-Babinga [δ136(H14)Gly → Asp; HBD: c.410G > A] (3.0%), Hb A2-Troodos [δ116(G18)Arg → Cys; HBD: c.349C > T] (1.0%), Hb A2-Coburg [δ116(G18)Arg → His; HBD: c.350G > A] (2.0%) and Hb A2-Indonesia [δ69(E13)Gly → Arg; HBD: c.208G > C] (1.0%). Three novel variants were identified: Hb A2-Calderdale [codon 2 (CAT > AAT), His → Asn; HBD: c.7C > A], Hb A2-Walsgrave [codon 52 (GAT > CAT), Asp → His; HBD: c.157G > C] and Hb A2-St. George's [codon 81 (CTC > TTC), Leu → Phe; HBD: c.244C > T]. In addition, two known δ-thal mutations were observed: -68 (C > T); HBD: c.-118C > T and codon 4 (ACT > ATT); HBD: c.14C > T. Amplification refractory mutation system (ARMS) primers were developed to provide a simple molecular diagnostic test for the most common variant, Hb [Formula: see text]. Three of the variants had a characteristic HPLC retention time that can be used for a presumptive diagnosis.

Molecular characterization of delta beta-thalassemia and hereditary persistence of fetal hemoglobin in the Indian population.

delta beta-Thalassemia (delta beta-thal) and hereditary persistence of fetal hemoglobin (HPFH) are heterogeneous disorders characterized by elevated levels of Hb F in adult life. The two disorders should not be considered as unambiguously separate entities but rather as a group of disorders with a variety of partially overlapping phenotypes. This study was undertaken to determine the hematological and molecular characteristics of high Hb F determinants among Indians. A gap-polymerase chain reaction (gap-PCR)-based approach was used for molecular characterization of high Hb F phenotypes. Fifty-five unrelated individuals were studied. The molecular findings were correlated with the hematological data. DNA analysis identified the deletion-inversion (G)gamma((A)gamma delta beta)(0)-thal in 15 cases (27%) and the HPFH-3 (Indian deletion) determinant in 26 cases (47.2%) and the Vietnamese/Chinese determinant (27 kb deletion) in five cases (9%), which is being reported for the first time from India; 16% (nine cases) of the samples remained uncharacterized. This study emphasizes that delta beta-thal and HPFH determinants are common in India. Molecular analysis will aid in understanding genotype-phenotype correlations and will facilitate prevention and control programs of thalassemia and hemoglobinopathies in this region.