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

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 β-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.

Molecular prevalence of HBB-associated hemoglobinopathy among reproductive-age adults and the prenatal diagnosis in Jiangxi Province, southern central China

Background and aims: Hemoglobinopathy associated with the HBB gene, with its two general subtypes as thalassemia and abnormal hemoglobin (Hb) variants, is one of the most prevalent hereditary Hb disorders worldwide. Herein we aimed to elucidate the prevalence of ß-thalassemia and abnormal hemoglobin variants and the prenatal diagnosis of the HBB gene in Jiangxi Province, southern central China.

Methods: Hematological indices and capillary Hb electrophoresis were conducted for 136,149 subjects who were admitted to Jiangxi Maternal and Child Health Hospital and requested for hemoglobinopathy investigation. Routine α- and ß-globin genotyping were performed by gap-polymerase chain reaction (Gap-PCR) and reverse dot-blot (RDB) hybridization for the 11,549 individuals suspected to be thalassemia carriers. For participants whose genotypes could not explain their hematological indices, further Sanger sequencing and Gap-PCR were conducted for the detection of rare or novel variants in related globin genes. Prenatal diagnosis was performed for 77 pregnant couples both carrying ß-thalassemia trait at appropriate gestational ages.

Results: Among the 11,549 subjects, 2,548 individuals were identified with HBB-associated hemoglobinopathy based on molecular analysis. A total of 2,358 subjects were identified as ß-thalassemia heterozygous carriers and nine cases were diagnosed as compound heterozygous ß-thalassemia. Additionally, 125 cases were detected with composite α- and ß-thalassemia and the remaining 56 individuals with abnormal Hb variants in the HBB. A total of 35 types of variants were identified in the HBB gene, including 26 types of ß-thalassemia and nine types of abnormal Hb variants. Four novel variants were firstly reported, including one variant in HBA2 and three variants in HBB. Overall, 77 prenatal samples underwent ß-thalassemia molecular diagnosis; 20 fetuses were identified with normal ß-thalassemia genotypes, 30 fetuses as ß-thalassemia heterozygotes, 11 as homozygotes, and 16 as compound heterozygotes in HBB.

Conclusion: We have demonstrated a relatively high prevalence rate at 1.872% of ß-hemoglobinopathies including common and rare ß-thalassemia as well as abnormal Hb variants among large child-bearing population in the Jiangxi area of southern central China for the first time. Our data presents that prenatal diagnosis is an effective way to prevent and control birth defects of ß-thalassemia.

Molecular and Haematological Characteristics of alpha-Thalassemia Deletions in Yogyakarta Special Region, Indonesia

Background

alpha-Thalassemia is caused primarily by deletions of one to two alpha-globin genes and is characterized by absent or deficient production of alpha-globin protein. The South-East Asia (SEA) deletion, 3.7-kb and 4.2-kb deletions are the most common causes. The present study aimed to observe the molecular characteristics of this common alpha-Thalassemia deletions and analyse its haematological parameter.

Methods

Blood samples from 173 healthy volunteers from thalassemia carrier screening in Yogyakarta Special Region were used. Haematological parameters were analysed and used to predict the carrier subjects. Genotype of suspected carriers was determined using multiplex gap-polymerase chain reaction and its haematological parameters were compared. The boundary site of each deletion was determined by analysing the DNA sequences.

Results

Seventeen (9.8%) of the volunteers were confirmed to have alpha-Thalassemia trait. Of these, four genotypes were identified namely -α^3.7/αα (58.8%), -α^4.2/αα (5.9%), -α^3.7/-α^4.2 (5.9%) and - -^SEA/αα (29.4%). The 5' and 3' breakpoints of SEA deletion were located at nt165396 and nt184700 of chromosome 16, respectively. The breakpoint regions of 3.7-kb deletion were 176-bp long, whereas for 4.2-kb deletion were 321-bp long. The haematological comparison between normal and those with alpha-Thalassemia trait genotype indicated a significant difference in mean corpuscular volume (MCV) (p< 0.001) and mean corpuscular haemoglobin (MCH) (p< 0.001). As for identifying the number of defective genes, MCH parameter was more reliable (p= 0.003).

Conclusion

The resultant molecular and haematological features provide insight and direction for future thalassemia screening program in the region.

Genetic research and clinical analysis of β-globin gene cluster deletions in the Chinese population of Fujian province: A 14-year single-center experience

BACKGROUND

Heterozygotes of HPFH and δβ thalassemia are clinically asymptomatic or have mild hemoglobin (Hb) values. However, when both HPFH and δβ-thalassemia are coinherited with heterozygous β-thalassemia, patients may progress to a clinical phenotype of thalassemia intermedia or thalassemia major. The purpose of this study was to characterize the genotypes and analyze the phenotypes of these disorders in Fujian Province, to offer advice for genetic counseling and accurate prenatal diagnosis in this region. A total of 55 001 subjects were participated in thalassemia screening. 142 subjects with HbF levels ≥10%, before the blood transfusion, were selected for further investigation.

METHODS

Multiplex ligation-dependent probe amplification (MLPA) and Gap-PCR were used to screen for three β-globin gene cluster deletions: Chinese ^G γ(^A γδβ)⁰ thalassemia and Southeast Asia HPFH (SEA-HPFH) deletion and 1357 bp deletion (NG-000007.3:g.69997-71353 del 1357).

RESULTS

A total of 142 patients with HbF (≥10%) were enrolled to characterize the molecular basis of β-globin gene cluster deletions in our study; 22 cases 0.04% (22/55 001) were definitively diagnosed with β-globin gene cluster deletions. Ten cases were heterozygous for the Chinese ^G γ(^A γδβ)⁰ -thal mutations, 10 cases were heterozygous for SEA-HPFH, and one case was compound heterozygous for SEA-HPFH and the α-thal mutation. The 1357 bp deletion (NG-000007.3:g.69997-71353 del 1357) was detected in one case. Moreover, the hemoglobin A₂  levels in patients who were heterozygous for Chinese ^G γ(^A γδβ)⁰ -thal were statistically lower than in cases with SEA-HPFH deletion(p < 0.05).

CONCLUSION

In Fujian Province, the prevalence of common β-globin gene cluster deletions was 0.04%. What's more, the most common β-globin cluster deletions are the Chinese ^G γ(^A γδβ)⁰ and SEA-HPFH.

Molecular Characterization Analysis of Thalassemia and Hemoglobinopathy in Quanzhou, Southeast China: A Large-Scale Retrospective Study

Background: There are limited reports available on investigations into the molecular spectrum of thalassemia and hemoglobinopathy in Fujian province, Southeast China. Here, we aim to reveal the spectrum of the thalassemia mutation and hemoglobinopathy in Quanzhou prefecture, Fujian province.

Methods: We collected data from a total of 17,407 subjects with the thalassemia trait in Quanzhou prefecture. Gap-PCR, DNA reverse dot blot hybridization, and DNA sequencing were utilized for common and rare thalassemia gene testing.

Results: In our study, we identified 7,085 subjects who were carrying thalassemia mutations, representing a detection rate of 40.70% (7,085/17,407). Among them, 13 different α-thalassemia gene mutations were detected, with the most common mutation being –^SEA (69.01%), followed by –α^3.7 (21.34%) and –α^4.2 (3.96%). We also discovered 26 β-thalassemia gene mutations, with the mutations of IVS-II-654 (C > T) (36.28%) and CD41/42(–TCTT) (29.16%) being the most prevalent. Besides, a variety of rare thalassemia variants were identified. Among them, the –^FIL, β^Malay, β^{IVS–I–130}, and β^{IVS–II–672} mutations were identified in Fujian province for the first time. Additionally, we detected 78 cases of hemoglobinopathies, of which Hb Owari was the first reported case in Fujian province and Hb Miyashiro was the first case identified in the Chinese population.

Conclusion: Our study indicates that there is a diverse range of thalassemia mutations, and it also reveals the mutation spectrum of rare thalassemia and hemoglobinopathies in Quanzhou, Fujian province. It provides valuable data for the prevention and control of thalassemia in Southeast China.

δ-Hemoglobinopathies in Thailand: screening, molecular basis, genotype-phenotype interaction, and implication for prevention and control of thalassemia

The δ-globin gene defects are clinically silent but interaction with β-thalassemia can lead to a misdiagnosis of β-thalassemia carrier. We report an extensive molecular characterization of δ-hemoglobinopathies in Thailand. Study was done on 32,108 subjects, encountered at the thalassemia screening. Six different approaches based on the reduced Hb A₂ or appearance of Hb A₂-derivative were established for selective recruitment of subjects. Among 32,108 subjects, a total of 296 subjects were suspected of having δ-globin gene defects. Of these 296 subjects, Hb and DNA analyses identified δ-hemoglobinopathies with 10 different mutations in 34 (0.11%) of them. These included a novel mutation, [δ^{CD30(AGG>GGG)} (n = 1)], 5 previously undescribed in Thailand, [δ^-44(G>A) (n = 7), Hb A₂-Troodos (n = 5), δ^{IVSII-897(A>C)} (n = 4), δ^-68(C>T) (n = 2), and Hb A₂-Indonesia (n = 1)], and 4 mutations previously found in Thailand, [Hb A₂-Melbourne (n = 9), δ^-77(T>C) (n = 3), Hb A₂' (n = 1), and Hb A₂-Kiriwong (n = 1)]. Genetic heterogeneities seen included interactions of δ-globin gene defects with heterozygous Hb E, β-thalassemia, α-thalassemia, and in cis locations of the Hb A₂-Troodos and Hb E mutations found for the first time. Rapid identification methods of these δ-globin gene mutations were developed. The results should prove useful to a prevention and control program of hemoglobinopathies in the region.

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, ‐α^3.7/αα, and ‐α^4.2/αα) were detected using Gap‐PCR, detection of the point mutations in the three nondeletional α‐thalassemia (α^CSα/αα,α^QSα/αα,α^WSα/αα), and the 17 common β‐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.