Analysis of δ-globin gene alleles in Tunisians: description of three new delta-thalassemia mutations.

BACKGROUND: Thalassemia is one of the most prevalent worldwide autosomal recessive disorders characterized by a great molecular and clinical expression heterogeneity. Alpha and beta-thalassemia are the main two types observed in case of mutations affecting alpha and beta-globin genes respectively. Delta-thalassemia is noted when mutations occur on the delta-globin gene. In Tunisia, ß-thalassemia prevalence is estimated at 2.21% of carriers. However, few reports investigated the delta-globin gene. OBJECTIVES: In this work, we aimed to perform a molecular study to help define the molecular spectrum of δ-thalassemia mutations in Tunisia. PATIENTS AND METHODS: The study involved 7558 patients among whom we selected 179 individuals with abnormal HbA2 values or fractions. Hemoglobin analysis was performed using Capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). DNA sequencing was performed on ABI prism 310 Genetic Analyzer Applied Biosystems. CUPSAT (Cologne University Protein Stability Analysis Tool) was used for the prediction of protein stability changes upon missense mutations and mutants were modeled via DeepView-SwissPdbViewer and POV-Ray softwares for molecular dynamics simulation studies. RESULTS: We identified four mutations: HbA2-Yialousa described for the first time in Tunisia ( in 72.72% of cases) and 3 mutations reported for the first time in the world: (i) c.442 T > C Stop147Arg ext 15aa-stop observed in 18.18% of cases, (ii) c.187 G > C (Ala62Pro) noted in 4.54% of cases and (iii) c.93-1G > C found in 4.54% of cases. CONCLUSION: Our data provide genetic basis that would be especially useful in screening for beta-thalassemia trait during delta-beta thalassemia associations.

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.

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.

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.

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.

Molecular and Hematological Characterization of Two Novel δ-Globin Gene Mutations Found in Chinese Individuals.

We identified two novel δ-globin gene mutations in two families during routine thalassemia screening. One missense mutation at codon 73 on the δ-globin gene [δ73(E17)Asp→Val, HBD: c.221A>T] which results in a Hb A2 variant homologous to the ß-globin gene variant called Hb Mobile [ß73(E17)Asp→Val, HBB: c.221A>T] and we have named this variant Hb A2-Henan. The other is a nonsense mutation [δ7(A4)Glu→Stop, HBD: c.22G>T] which gives rise to a stop codon (TAG) at codon 7, resulting in δ0-thalassemia (δ0-thal). The Hb A2 in one individual with homozygous HBD: c.22G>T was absent.

[Analysis of haematological phenotype and mutation spectrum of δ-globin gene from Guangdong area in Chinese Han prenatal population].

Objective: To analyze the genotype-phenotype correlations among southern Chinese Han prenatal population in Guangdong area with δ-globin gene mutation, so as to enrich the delta-thalassemia gene mutations data. Methods: A total of 33 cases were selected in 7 580 patients during prenatal thalassemia trait screening, from January 2012 to May 2015(including 10 males and 23 females, aged 22-48 years old). Complete blood cell count was performed on a XE 4000i automatic hemocyte analyzer. Hb, HbF and HbA2 were tested by high performance liquid chromatography (HPLC). Genomic DNA was extracted from whole blood samples using a whole blood genomic DNA extraction kit. Polymerase chain reaction (PCR) was used to amplify three different fragments corresponding to the exons and the regulatory sequences using three different couples of primers for the δ-globin gene. Results: Twenty one of the 33 samples were positive for the δ-globin gene defects. Four previously known mutations were detected: including 12 cases for -77(T>C)[HBD c. -127 (T>C)](57.14%), 4 cases for -30 (T>C)[HBD c. -80 (T>C)](19.05%), 1 case for codon 10 (-G) (HBD c. 31delG)(4.76%), and 1 case for HBD c. 244 C>T(4.76%). Three new δ-globin gene defects which had not yet been reported in database were detected, including 1 case for HBD c. 22_24delGAG(4.76%), 1 case for HBD c. 347 C>T(4.76%), and one case for HBD c. 349 C>G(4.76%). Conclusions: -77 (T>C) is the most common mutation in Chinese southern prenatal population. Three new HBD gene mutations are referred in this report, which provide the valuable information for genetic counseling and prenatal diagnosis in Guangdong area.

The New -474(C→T) Substitution Discovered in the HBG2 Promoter of a Sardinian δß-Thalassemia Carrier.

During a screening for hemoglobinopathies, we found a carrier of the Sardinian δß-thalassemia condition. The proband's hematology and hemoglobin (Hb) profile agreed with those of the other carriers previously identified during our diagnostic program except for the fetal Hb (HbF) composition, which consisted of both α2Aγ2 and α2Gγ2 instead of nearly 100% α2Aγ2. In order to explain the unusual γ-chain ratio, sequencing of the Gγ promoter was carried out and revealed two nucleotide substitutions in cis: C→T at position -474 and A→G at position -309 from the Cap site. The latter had previously been observed in subjects with raised HbF levels, although it has not yet been evaluated at functional level. We used the luciferase assay to determine whether the two mutations modify the transcriptional activity of the Gγ promoter. Results indicated that the observed in vivo Gγ-globin production cannot be translated into increased in vitro promoter function, suggesting that the assessed mutations cannot be considered as functional single nucleotide polymorphisms per se; instead, a more complex regulatory mechanism might be involved.

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.

Sudanese (뫧)0-Thalassemia: Identification and Characterization of a Novel 9.6 kb Deletion.

We report a case of δß-thalassemia (δß-thal) trait in an adult male originally from Sudan. Multiplex ligation-dependent probe amplification (MLPA) was used to localize the approximate boundaries of the deletion, followed by polymerase chain reaction (PCR) amplification and sequence analysis of the junction fragment to determine the precise deletion endpoints. The deletion spans 9594 bp, with the 5' deletion endpoint located 1560 bp upstream of the δ-globin gene and the 3' endpoint within the second intervening sequence (IVS-II) of the ß-globin gene.

[Testicular Tumor in a Patient with Delta Thalassemia Complicated with Hereditary Persistence of Fetal Hemoglobin].

A 30s male was diagnosed as having the left testicular tumor in 2010. He received the anti-neoplastic chemotherapy, and could achieve the complete remission. But, he relapsed with solitary retroperitoneal lymph node swelling in 2012, and he was referred to our hospital. Laboratory examination on his admission showed the significant increase of fetal hemoglobin (HbF) up to 16.4%. But, neither anemia nor hemolysis was found at that time. Coexistence of therapy-related myeloid neoplasm or HbF production by metastatic lesion was not definite. Isoelectrofocusing of his hemolysate showed the faint HbA2 in addition to dense HbF band. Molecular analysis of his Hb gene revealed the homozygous (G)gamma-158 (C-T) together with homozygous delta-77(T-C). From these findings, he was diagnosed as having hereditary persistence of HbF (HPFH) and homozygous delta thalassemia. The precise incidence of such combined genetic variation has been unknown because the majority of such cases seem to show no significant clinical symptoms as our case. Whereas, it seems necessary to remind the possibility of such genetic variation when adult patients with various acquired diseases such as testicular tumor or hematologic malignancies show the elevated HbF level.

εGγAγδß0-thalassemia: a rare but clinically significant cause of hemolytic anemia in infants.

Normal hemoglobin is made of a tetramer of 2 α-globin and 2 ß-globin polypeptide chains. Deletions in the ß-globin gene cluster can range from a few hundred base pairs to loss of the entire cluster resulting in rare, but clinically significant, thalassemias. One such entity is εGγAγδß0-thalassemia, a condition that presents within the first few weeks of life as a Coombs-negative hemolytic anemia and is not identified on routine newborn screening or hemoglobin electrophoresis.

Known and new δ-globin gene mutations and other factors influencing Hb A2 measurement in the Omani population.

Although δ-thalassemia (δ-thal) is not categorized as a severe disease, it is essential to know the molecular spectrum of the δ gene mutations frequently occurring in specific areas, particularly if these areas are characterized by a high rate of ß-thalassemia (ß-thal) such as Oman. This is because coinherited δ-globin gene defects can interfere with the basic diagnosis of a ß-thal carrier when this is based upon the measurement of the Hb A2 only. Because of that, we have investigated 33 patients with low Hb A2 levels, collected from different hospitals in Oman. Some cases had a second Hb A2 fraction, while others had only significantly lower Hb A2 levels. Among these patients, 20 did carry a δ-globin gene mutation, the rest were carriers of α thalassemia (α-thal) defects or could be iron depleted or both. In total, eight different known mutations and two novel δ variants were found. The characterization of the δ-globin gene mutation spectrum will improve carrier diagnostics and genetic counseling in the Omani population screened for ß-thal.

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.

Hb SKMC and an unprecedented γδß-thalassemia: first report from Iraq.

BACKGROUND: Thalassemias are genetic disorders of globin chain synthesis. In Iraq, ß-thalassemia is more prevalent than α-thalassemia. This study identifies two unpredicted globin gene mutations, a rare α-globin gene mutation (Hb SKMC) and a novel γδß-thalassemia deletion. METHODS: Over 2 years, the Genetics unit at PAR hospital in Erbil, northern Iraq processed 137 ß-thalassemia and 97 α-thalassemia genetic testing requests. Three symptomatic thalassemia cases with unreported genotypes were identified. Proband-1α and proband-2α had Hb H disease, while proband-1ß had severe transfusion-dependent ß-thalassemia (TDT). Molecular studies included multiplex PCR, reverse hybridization, multiplex ligation-dependent probe amplification (MLPA), and globin gene sequencing. RESULTS: The α-thalassemia probands exhibited moderate microcytic hypochromic anemia with irregular transfusions and splenomegaly. Hb H disease was confirmed by positive Hb H tests and high-performance liquid chromatography (HPLC). Molecular analysis revealed heterozygous -MED deletion in proband-1α and α2Poly-A2 mutation in proband-2α. Sequencing identified the Hb SKMC (HBA1:c.283_300+3dup) mutation in both probands. The ß-thalassemia proband showed anemia and regular transfusions. Molecular studies detected the IVS1.110 G>A mutation and a novel γδß-thalassemia deletion in compound heterozygous form. The maternal sample showed the IVS1.110 G>A mutation, and MLPA confirmed the γδß-thalassemia deletion in the paternal sample. CONCLUSION: These findings highlight the genetic diversity of thalassemias in the region and emphasize the importance of advanced molecular diagnostics in detecting rare mutations.

Two complex associations of an HBD mutation and a rare α hemoglobinopathy.

We present two case reports in which an HBD mutation is present with a rare α hemoglobinopathy that substantially complicates the associated phenotype. In the first case, a new δ-globin variant, Hb A2-Pierre-Bénite [δ83(EF7)Gly→Arg; HBD: c.250G>C] is associated with Hb Groene Hart [α119(H2)Pro→Ser (α1); HBA1: c.358C>T], an α-thalassemic variant. In the second case, a δ(+)-thalassemic variant, δ4(A1)Thr→Ile; HBD: c.14C>T, is associated with a newly described deletion of the hypersensitive site 40 (HS-40) region on the α-globin gene cluster. In both patients, a δ-globin mutation was suspected because of an abnormally low Hb A2 level, whereas the α hemoglobinopathy was sought to explain the slight microcytosis and hypochromia presented by the probands.

Erythrocytosis in a child due to Hb Andrew-Minneapolis [ß144(HC1)Lys→Asn (AAG>AAT or AAC)] associated with a Spanish (δß)(0)-thalassemia.

We report a rare association of δß-thalassemia (δß-thal) and a hemoglobin (Hb) variant with high oxygen affinity in a Spanish newborn. The proband had no Hb A and showed microcytosis and hypochromia; the peripheral blood smear was compatible with a thalassemia trait. Molecular studies revealed that the proband had a Spanish (δß)(0)-thal (inherited from his father) and also carried a de novo variant (Hb Andrew-Minneapolis) because from the point of hematology, his mother was quite normal. The hemoglobinopathies with high affinity for oxygen constitute an infrequent cause of secondary congenital erythrocytosis. The degree of erythrocytosis and the resulting clinical manifestations are highly variable, depending on the degree of altered oxygen affinity and the presence of thalassemic genes. Thus, when these variants are associated with ß(0)- or δß-thal, as in our case, the proportion of abnormal Hb is ∼100.0%, which may cause polycythemia, hyperviscosity, and iron deficiency. This type of association is very rare and few have been described, especially in children, as they would normally be detected in adults as the increased packed cell volume (PCV) also increases blood viscosity and causes the typical symptoms (cephalalgia, drowsiness, dizziness). The association of a high oxygen affinity Hb and a δß-thal presents a greater degree of erythrocytosis than when this same variant is associated with a ß(0)-thal, mainly because the Hb F percentage is usually greater in the δß-thal, and Hb F normally shows a greater affinity for oxygen and a reduced P(50), although one must always take into account the degree of oxygen affinity of the Hb variant. Familial erythrocytosis and an abnormal electrophoresis finding are indicative of a high affinity Hb. However, the absence of these findings does not reject the possibility of hemoglobinopathies, and in these cases, functional and molecular studies would be justified and should be mandatory for the differential diagnosis of erythrocytosis.

Molecular characterization of a novel homozygous deletion in ß-globin cluster causing (δß)0-Thalassemia among Tunisian family.

BACKGROUND: Deletions in the ß-globin cluster are uncommon and cause thalassemia (thal) with hereditary persistence of fetal hemoglobin. They constitute a heterogenous group of disorders characterized by absent or reduced synthesis of adult hemoglobin (Hb A) and increased synthesis of fetal hemoglobin (Hb F). Although the clinical severity of these disorders are asymptomatic owing to the increased Hb F levels, the molecular basis is very heterogenous due to the large deletions in the ß-globin cluster spanning both HBD and HBB genes. Here, we describe a Tunisian family carrying a novel deletion mutation causing (δß)°-thalassemia. METHODS: The amounts of hemoglobin fractions were measured by capillary electrophoresis of hemoglobin. Amplification and sequencing of different regions on the ß-gene cluster were performed by Sanger method. RESULTS: Family study and genetic analysis revealed a large deletion mutation in the ß-globin cluster of 14.5 kb (NG_000,007.3:g. 58,253 to g.72837del14584) at the homozygous state in the patient and at heterozygous state at the other members of the family. This deletion removes the HBD and HBB genes. CONCLUSIONS: In our knowledge, this new large deletion is described for the first time in the Tunisian population and in the world, designed Tunisian(δß)0 in Ithanet database (IthaID: 3971). Therefore, it is important to identify the deletion leading to δß-thalassemia carriers at the molecular level, to highlight the importance of recognizing the clinical features and implementing appropriate testing to clarify the diagnosis and manage the condition.

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.