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

BACKGROUND: Heterozygotes of HPFH and 뫧 thalassemia are clinically asymptomatic or have mild hemoglobin (Hb) values. However, when both HPFH and δß-thalassemia are coinherited with heterozygous ß-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 ß-globin gene cluster deletions: Chinese G γ(A γδß)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 ß-globin gene cluster deletions in our study; 22 cases 0.04% (22/55 001) were definitively diagnosed with ß-globin gene cluster deletions. Ten cases were heterozygous for the Chinese G γ(A γδß)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 γδß)0 -thal were statistically lower than in cases with SEA-HPFH deletion(p < 0.05). CONCLUSION: In Fujian Province, the prevalence of common ß-globin gene cluster deletions was 0.04%. What's more, the most common ß-globin cluster deletions are the Chinese G γ(A γδß)0 and SEA-HPFH.

A Novel 5 kb Deletion in the ß-Globin Gene Cluster Identified in a Chinese Patient.

ß-Thalassemia (ß-thal), a highly prevalent disease in tropical and subtropical regions of Southern China, is caused mainly by point mutations in the ß-globin gene cluster. However, large deletions have also been found to contribute to some types of ß-thal. We identified a novel 5 kb deletion in the ß-globin cluster in a Chinese patient using multiplex ligation-dependent probe amplification (MLPA), and characterized it with single molecule real-time (SMRT) sequencing, gap-polymerase chain reaction (gap-PCR) and Sanger sequencing. The deletion was located between positions 5226189 and 5231091 on chromosome 11 (GRCh38), extending from 4 kb upstream of the 5' untranslated region (5'UTR) to the second intron of the ß-globin gene. The patient with this deletion presented with microcytosis and hypochromic red cells, as well as relatively high Hb F and Hb A2 levels. Our research indicated that SMRT sequencing is a useful tool for accurate detection of large deletions. Our study broadens the spectrum of deletional ß-thalassemias and provides a perspective for further study of the function of the ß-globin cluster.

Hb F Levels in ß-Thalassemia Carriers and Normal Individuals: Known and Unknown Quantitative Trait Loci in the ß-Globin Gene Cluster.

In the already identified quantitative trait loci (QTL), modulating Hb F levels are cis-acting haplotypes of the ß-globin gene cluster itself, although the single nucleotide polymorphisms (SNPs) accounting more for the association, remain uncertain. In this study, the role in Hb F production of previously reported candidate SNPs within the ß-globin gene cluster was reexamined, along with a yet poorly studied variation in the BGLT3 gene. In a sample of ß-thalassemia (ß-thal) carriers, we succeeded in replicating the significant association between increased Hb F levels and rs7482144 (C>T) (HBG2 XmnI), which is the most well-established variation in the cluster influencing the trait. This SNP was found to be in strong linkage disequilibrium (LD) with a variation in the HBBP1 gene [rs10128556 (G>A)], which consistently revealed a similar association signal. Remarkably, much stronger than the latter associations were those involving both rs968857 (T allele) (3' HBBP1) and rs7924684 (G allele) (BGLT3), two SNPs that were also in strong LD. As the pattern of LD detected in the ß-globin gene cluster does not correlate with a tight linkage between markers, complex interactions between SNPs at the cluster seem to modulate Hb F. Seeing that no such associations were detected in normal subjects, the question can be raised on whether, under erythropoiesis stress, epigenetic mechanisms contribute to change the regulation of the entire ß-globin gene cluster. In conclusion, we provide statistical evidence for a new player within the ß-globin gene cluster, BGLT3, that in cooperation with other regions influences Hb F levels in ß-thal carriers.

Profiling of 35 Cases of Hb S/Hb E (HBB: c.20A>T/HBB: c.79G>a), Disease and Association with α-Thalassemia and ß-Globin Gene Cluster Haplotypes from Odisha, India.

Hb S/Hb E (HBB: c.20A>T/HBB: c.79G>A) is an uncommon variant of sickle cell disease resulting from coinheritance of Hb S and Hb E. Clinico-hematological and biochemical parameters of 35 cases of Hb S/Hb E disease were studied and compared with 70 matched cases of homozygous sickle cell disease (Hb SS) and Hb S/ß-thalassemia (ß-thal) with IVS-I-5 (G>C) (HBB: c.92+5G>C). The influence of α-thal and that of of ß-globin gene cluster haplotypes among Hb S/Hb E disease was also studied. Statistical analysis was done using GraphPad InStat version 3.06. Of the 35 cases, 20 (57.14%) had a moderate clinical presentation. Mean lactate dehydrogenase (LDH) level, vaso-occlusive crises (VOCs) per year, and annual blood transfusion requirements were significantly lower in Hb S/Hb E cases than in the other two groups. The hemoglobin (Hb) and packed cell volume (PCV) levels were significantly high in Hb S/Hb E cases with α-thal and these cases were associated with microcytic-hypochromic anemia. α-Thalassemia did not influence clinical presentation in Hb S/Hb E cases. The ß-globin gene cluster haplotypes of 70 alleles of Hb S/Hb E revealed an association of five typical haplotypes [Arab-Indian (A-I), Benin, Bantu, Cameroon and Senegal] in 95.71% cases. Hb S/Hb E disease exhibit asymptomatic to moderate phenotypic expression. However, further in-depth studies on Hb S/Hb E will help in reducing the disease burden especially in high-risk countries like India.

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.

ß-Thalassemia Haplotypes in Romania in the Context of Genetic Mixing in the Mediterranean Area.

The purpose of this meta-study was to investigate ß-thalassemia (ß-thal) mutations and their chromosomal background in order to highlight the origin and spread of thalassemia alleles in the European and Mediterranean areas. Screening of more than 100 new Romanian ß-thal alleles was also conducted. The results suggest an ancient introduction of mutations at codon 39 (C > T) (HBB: c.118C > T) and IVS-I-6 (T > C) (HBB: c.92 + 6T > C) in Romania. A comparative study was performed based on restriction fragment length polymorphism (RFLP) haplotypes associated with ß-thal mutations in Romania and in Mediterranean countries. Each common ß-thal allele from different populations exhibits a high degree of haplotype similarity, a sign of a clear unicentric origin for the IVS-I-110 (G > A) (HBB: c.93-21G > A), IVS-I-6, IVS-II-745 (C > G) (HBB: c.316-106C > G) and codon 39 mutations (the 17a [+ - - - - + +], 13c [ - + + - - - +], 17c [ + - - - - - +] and 14a [- + + - + + + ] ancestral RFLP background, respectively), followed by recurrent recombination events. This study also showed that geographic distances played a major role in shaping the spread of the predominant ß-thal alleles, whereas no genetic boundaries were detected between broad groups of populations living in the Middle East, Europe and North Africa. The analyses revealed some discrepancies concerning Morocco and Serbia, which suggest some peculiar genetic flows. Marked variations in ß(A) were observed between Southeast Asia and the Mediterranean, whereas a relative genetic homogeneity was found around the Mediterranean Basin. This homogeneity is undoubtedly the result of the high level of specific historic human migrations that occurred in this area.

A homotetrameric hemoglobin expressed in alveolar epithelial cells increases blood oxygenation in high-altitude plateau pika (Ochotona curzoniae).

The plateau pika (Ochotona curzoniae) is native to the Qinghai-Tibet Plateau. In this study, the gene that encodes a heme-binding protein in the pulmonary surfactant (PS) of the pika is identified. The protein is a homotetrameric hemoglobin (δ4) encoded by HBD (δ). HBD is expressed in alveolar epithelial type II (ATII) and type I (ATI) cells, upregulated by hypoxia. δ4 is secreted into alveolar cavities through osmiophilic multilamellar bodies. HBD expression is downregulated by RNAi, which significantly increases hypoxia-inducible factor 1α expression in lung tissue and red blood cells and hemoglobin and blood lactate concentrations but significantly decreases arterial partial pressure of oxygen (PaO2). Our results indicate that plateau pikas physiologically show hypoxemia when HBD expression is downregulated. Therefore, specific HBD expression in the lungs helps plateau pikas to obtain oxygen under hypoxia by maintaining higher PaO2. These findings provide insights into the adaptive mechanisms of plateau pikas to withstand high-altitude environments.

Time estimations by network of beta globin gene cluster haplotypes linked with Hb D-Los Angeles [ß121 (GH4) Glu → Gln GAA → CAA] mutation in the world populations.

BACKGROUND: ß-Globin gene cluster haplotypes associated with the Hb D-Los Angeles mutation have been reported in many different locations in different populations including Italy, Iran, Thailand, Belgium, Mexico, Holland, and Turkey. In this study, we have identified genetic relationships and formation periods between the haplotypes reported in the world regarding the Hb D-Los Angeles. METHODS: We comparatively analyzed the RFLP (restriction fragment length polymorphism) data in Denizli region and world populations using Arlequin 3.5 statistical software program. The data obtained from the Arlequin software were then entered into the Phylogenetic Network software to calculate the age estimates and to discover possible links between the haplotypes. RESULTS: We observed the frequencies of the ß-globin gene haplotypes for the seven polymorphic restriction sites around the world and calculated the estimated time of haplotypes using Network software on the basis of ancestral haplotypes. We performed the phylogenetic network analysis of the haplotypes linked with Hb D-Los Angeles mutation by processing the data of frequency and age estimations with Network software. CONCLUSION: Our period of time results suggests that HAP1 was formed before modern human migration to Asia and/or independent origin of the Hb D-Los Angeles mutation from other populations. Considering that the population in Denizli region started the Hb D-Los Angeles mutation past about 40,000 years ago, it can be said that HAP1, HAP15, and HAP21 belong to the gene pool with an external effect. Our period of time results of HAP6 is compatible with published dating results.

Heterozygosis deficit of polymorphic markers linked to the ß-globin gene cluster region in the Iranian population.

OBJECTIVES: Iran is considered as one of the high-prevalence areas for ß-thalassemia with a rate of about 10% carrier frequency. Molecular diagnosis of the disease is performed both by direct sequencing and indirectly by the use of polymorphic markers present in the beta globin gene cluster. However, to date there is no reliable information on the application of the markers in the Iranian population. Here we report the results of an extended molecular analysis of five RFLP markers, XmnI, HindIIIA, HindIIIG, RsaI and HinfI, located within the ß-globin gene cluster region in four subpopulations of Iran. MATERIALS AND METHODS: A total of 552 blood samples taken from the Iranian subpopulations including Isfahan, Chaharmahal-O-Bakhtiari, Khuzestan and Hormozgan were genotyped using PCR-RFLP and sequencing. The allele frequency, the expected and observed heterozygosity, and Shannon's information index (I) of these markers were calculated. RESULTS: Distribution of the allele frequencies for XmnI, HindIIIA, HindIIIG, RsaI and HinfI polymorphic markers did not differ significantly among the subpopulations examined. Overall observed heterozygosity ranged from 0.1706 for HindIIIA to 0.4484 for RsaI. The Shannon index was <1 for all the polymorphic markers in the populations studied. The data indicated that heterozygosity of these markers was low in the Iranian population. CONCLUSION: The results suggested that genotyping of these markers is not informative enough once used as single markers for prenatal diagnosis and carrier detection of ß-thalassemia in the Iranian population. However, haplotyping of these markers may provide more useful data in linkage analysis and prenatal diagnosis as well as carrier detections for ß-thalassemia in Iranians.

Fetal Haemoglobin and ß-globin Gene Cluster Haplotypes among Sickle Cell Patients in Chhattisgarh.

BACKGROUND: Foetal Haemoglobin (HbF) is the best-known genetic modulator of sickle cell anaemia, which varies dramatically in concentration in the blood of these patients. The patients with SCA display a remarkable variability in the disease severity. High HbF levels and the ß-globin gene cluster haplotypes influence the clinical presentation of sickle cell disease. To identify the genetic modifiers which influence the disease severity, we conducted a ß-globin haplotype analysis in the sickle cell disease patients of Chhattisgarh. AIM: The foetal haemoglobin and the ß-globin gene haplotypes of the sickle cell trait and the sickle cell disease patients from Chhattisgarh were investigated. MATERIALS AND METHOD: A total of 100 sickle cell patients (SS), 50 sickle cell trait patients (AS) and 50 healthy control individuals were included in the present study. The distribution of the ß-globin gene haplotype was done by the PCR-RFLP method. RESULT: PCR-RFLP showed that the homozygous Arab-Indian haplotype (65%) was the most frequent one, followed by the heterozygous Arab-Indian haplotype (11%) in the sickle cell patients (SS), while the AS patients had a higher frequency of the heterozygous Arab-Indian haplotype (38%) in comparison to homozygous one (32%). Four atypical haplotypes, 3 Benin and 1 Cameroon were also observed, although they were in lower frequencies. In the present study, the HbF levels were higher in the AS and the SS patients, with one or two Arab-Indian haplotypes as compared to the other haplotypes. CONCLUSION: The presence of the Arab-Indian haplotype as the predominant haplotype might be suggestive of a gene flow to/from Saudi-Arabia or India and it was associated with higher HbF levels and a milder disease severity.