Restriction mapping of βS locus among Tunisian sickle-cell patients

To Study the β-Globin Haplotype Pattern of Descent of a Set of Linked Alleles Occurring on the Same Chromosome in the Northern Province of India

OBJECTIVE

To study the five mutations commonly prevalent in North India, i.e., IVS-I-5 (G→C), 619 bp deletion, IVS-I-1 (G→T), codon 41/42 (-TTCT), and codon 8/9 (+G), in the beta thalassemia (β-thalassemia) major children. The specific β-thalassemia mutations of different haplotype patterns of the β-globin gene cluster will also be determined.

METHODS

A total of 125 children diagnosed with β-thalassemia major visiting the Department of Pediatrics of King George's Medical University were involved in the study. As per the QIAamp (Qiagen, Hilden, Germany) manufacturer guidelines, genomic DNA was isolated from whole blood. To identify the haplotype pattern within the β-globin gene cluster, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was used. The respective restriction endonucleases used were Hind III/GƔ, Hinc II/Ψß, Hinf I/ß, Ava II/ß, and BamHI for the haplotype analysis in the β-globin pattern of descent of a set of linked alleles occurring on the same chromosome.

RESULTS

Among the five common mutations, 73 patients had IVS-I-5 (G→C), 28 patients had 619 bp deletion, 17 patients had IVS-I-1 (G→T), five patients had Cd 41/42 (-TTCT), and two patients had Cd 8/9 (+G) mutations. Fifteen haplotypes (haplotypes 1-15) were identified in 125 β-thalassemia major children. Among the five haplotypes observed in the IVS-I-5 (G→C) mutation, the H1 haplotype was most predominant with a frequency of 27.2%, followed by the H2, H4, H3, and H10 haplotypes in the given population. In 619 bp deletion, IVS-I-1 (G→T), codon 41/42, and codon 8/9, haplotype H9, H12, H11, and H5 were seen, respectively.

CONCLUSION

β-thalassemia was found to be the most common in the northern province of Uttar Pradesh. The linkage of β-globin gene haplotypes with β-thalassemia mutations was explored in the northern province of Uttar Pradesh. The population of different natives is being mixed up due to migration and industrialization. These were some reasons for the occurrence of haplotypic heterogeneity. This haplotype heterogeneity was correlated with the origin of these mutations found to be unlike the origin of common ones from different provinces.

Molecular characterization of a novel homozygous deletion in β-globin cluster causing (δβ)0-Thalassemia among Tunisian family

BACKGROUND

Deletions in the β-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 β-globin cluster spanning both HBD and HBB genes. Here, we describe a Tunisian family carrying a novel deletion mutation causing (δβ)°-thalassemia.

METHODS

The amounts of hemoglobin fractions were measured by capillary electrophoresis of hemoglobin. Amplification and sequencing of different regions on the β-gene cluster were performed by Sanger method.

RESULTS

Family study and genetic analysis revealed a large deletion mutation in the β-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(δβ)⁰ in Ithanet database (IthaID: 3971). Therefore, it is important to identify the deletion leading to δβ-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.

Molecular Analysis of Xmn1-Polymorphic Site ´5 to Gγ of the β-Globin Gene Cluster in a Saudi Population of Jazan Region in Correlation with Hb F Expression

The southern part of Saudi Arabia has an ethnically diverse population where sickle-cell anemia (sickle cell disease) is common, but little is known about its βs haplotypes. The goal of the current study is to ascertain the prevalence of the Hb S gene with analysis of Xmn1 ′5 to Gγ haplotype among the Saudi population in the Jazan area. Initially recorded findings of (1) Hb S gene and (2) hematological parameters with Hb F levels were collected from 5990 participants. Then, the second series of 70 different patients with established sickling disease and 30 healthy individuals as a control group was recruited, in which the genotype of Xmn1 ′5 to Gγ-SNP was performed by PCR-RFLP. In the first series, the prevalence of Hb types was AA at 86.8% (N = 5198), AS at 12.4% (N = 745), and SS at 0.8% (N = 47). Of the second series, three patients (4.3%) were (±) Xmn1 ′5 to Gγ and 67 (95.7%) were (−/−) in Xmn1 ′5 to Gγ. In the controls, the (±) Xmn1 ′5 to Gγ was observed in only one individual (3.3%), aged 30. These findings possibly represent a new Saudi haplotype, [±] Xmn1 ′5 to Gγ. Our results demonstrate that most patients with SCD in Jazan have [−/−] Xmn1 with higher levels of Hb F and positive Xmn1 ′5 to Gγ normally associated with a low level of Hb F.

Haplotype Analysis of β-Thalassaemia Major and Carriers with Filipino β°-Deletion in Sabah, Malaysia

Objective

The Filipino β°-deletion has been reported as a unique mutation in East Malaysia with a severe phenotype due to the complete absence of β-globin chain synthesis. In this study, the haplotype patterns of the β-globin gene cluster were used to relate the human genetic variation to this specific β-thalassaemia mutation.

Methods

The 376 study subjects included 219 β-thalassaemia major (β-TM) patients with homozygous Filipino β°-deletion and 157 carriers with heterozygous Filipino β°-deletion from 10 government hospitals in different regions of Sabah. Genomic DNA was isolated from whole blood using silica membrane based DNA purification protocol. Polymerase chain reaction restriction fragment length polymorphism analysis (PCR-RFLP) was conducted on five markers within the β-globin gene cluster to construct the haplotype patterns.

Results

Four haplotypes (Haplotype I–IV) were identified with Haplotype I as the predominant haplotype with the highest frequency of 0.98, followed by Haplotype II, III and Haplotype IV with 0.02. Haplotype I was strongly linked with the Filipino β°-deletion among the indigenous population.

Conclusion

Haplotype I as the predominant haplotype suggests the patients with the Filipino β°-deletion in Sabah have a similar origin.

The effects of old and recent migration waves in the distribution of HBB*S globin gene haplotypes

Sickle cell hemoglobin is the result of a mutation at the sixth amino acid position of the beta (β) globin chain. The HBB*S gene is in linkage disequilibrium with five main haplotypes in the β-globin-like gene cluster named according to their ethnic and geographic origins: Bantu (CAR), Benin (BEN), Senegal (SEN), Cameroon (CAM) and Arabian-Indian (ARAB). These haplotypes demonstrated that the sickle cell mutation arose independently at least five times in human history. The distribution of βS haplotypes among Brazilian populations showed a predominance of the CAR haplotype. American populations were clustered in two groups defined by CAR or BEN haplotype frequencies. This scenario is compatible with historical records about the slave trade in the Americas. When all world populations where the sickle cell gene occurs were analyzed, three clusters were disclosed based on CAR, BEN or ARAB haplotype predominance. These patterns may change in the next decades due to recent migrations waves. Since these haplotypes show different clinical characteristics, these recent migrations events raise the necessity to develop optimized public health programs for sickle cell disease screening and management.

Beta-globin gene haplotypes among cameroonians and review of the global distribution: is there a case for a single sickle mutation origin in Africa?

Studies of hemoglobin S haplotypes in African subpopulations have potential implications for patient care and our understanding of genetic factors that have shaped the prevalence of sickle cell disease (SCD). We evaluated HBB gene cluster haplotypes in SCD patients from Cameroon, and reviewed the literature for a global distribution. We reviewed medical records to obtain pertinent socio-demographic and clinical features for 610 Cameroonian SCD patients, including hemoglobin electrophoresis and full blood counts. RFLP-PCR was used to determine the HBB gene haplotype on 1082 chromosomes. A systematic review of the current literature was undertaken to catalogue HBB haplotype frequencies in SCD populations around the world. Benin (74%; n = 799) and Cameroon (19%; n = 207) were the most prevalent haplotypes observed among Cameroonian patients. There was no significant association between HBB haplotypes and clinical life events, anthropometric measures, hematological parameters, or fetal hemoglobin (HbF) levels. The literature review of the global haplotype distributions was consistent with known historical migrations of the people of Africa. Previously reported data from Sudan showed a distinctly unusual pattern; all four classical haplotypes were reported, with an exceptionally high proportion of the Senegal, Cameroon, and atypical haplotypes. We did not observe any significant associations between HBB haplotype and SCD disease course in this cohort. Taken together, the data from Cameroon and from the wider literature suggest that a careful reassessment of African HBB haplotypes may shed further light on the evolutionary dynamics of the sickle allele, which could suggest a single origin of the sickle mutation.

Fetal Hemoglobin in Tunisian Sickle Cell Disease Patient: Relationship with Polymorphic Sequences Cis to the β-Globin Gene

Fetal hemoglobin (HbF) plays a dominant role in ameliorating morbidity and mortality of hemoglobinopathies. We evaluated the effects of polymorphic markers within the β-globin gene cluster to identify the genetic mechanics that influence HbF on Tunisian sickling patients (n = 242). Haplotype analysis was carried out by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and the framework polymorphism was established by PCR-sequencing, four independent regions of interest were identified: the 5' region of β-LCR-HS2 site, the intervening sequence II (IVSII) region of two fetal (Gγ and Aγ) genes and the 5' region of β-globin gene. The correlation of these various Haplotypes and SNPs with HbF expression and clinical data was studied. Our data showed that among the various polymorphic markers analyzed, only the sequence (AT)xN12(AT)y in LCR HS2 region was significantly associated (p < 0.05) with increased HbF levels, suggesting that the β-globin gene cluster exerts a significant effect on HbF in sickle cell patients. This study can improve understanding of the physiopathology of the disease and aid to increase our ability to predict clinical severity.

Haplotype map of sickle cell anemia in Tunisia

β-Globin haplotypes are important to establish the ethnic origin and predict the clinical development of sickle cell disease patients (SCD). To determine the chromosomal background of β^S Tunisian sickle cell patients, in this first study in Tunisia, we have explored four polymorphic regions of β-globin cluster on chromosome 11. It is the 5′ region of β-LCR-HS2 site, the intervening sequence II (IVSII) region of two fetal (^Gγ and ^Aγ) genes and the 5′ region of β-globin gene. The results reveal a high molecular diversity of a microsatellite configuration describing the sequences haplotypes. The linkage disequilibrium analysis showed various haplotype combinations giving 22 “extended haplotypes”. These results confirm the utility of the β-globin haplotypes for population studies and contribute to knowledge of the Tunisian gene pool, as well as establishing the role of genetic markers in physiopathology of SCD.

Early complication in sickle cell anemia children due to A(TA)nTAA polymorphism at the promoter of UGT1A1 gene

Aim. To determine the implication of the polymorphism, namely, A(TA)_nTAA of UGT1A1 in lithogenesis for the first time in Tunisia among sickle cell anemia (SCA) children patients. Material and Methods. Our study was performed in 2010 and it involved 76 subjects chosen as control group characterized with normal hemoglobin status and presence of cholelithiasis and 102 SCA pediatric patients among whom 52 have cholelithiasis. We analyzed the polymorphism A(TA)_nTAA at the UGT1A1 promoter and the relationships between the various A(TA)_nTAA genotypes and alleles and bilirubin levels and occurrence of cholelithiasis. Results and Discussion. The repartition of genotypes found according to serum bilirubin level shows a significant association between genotypes carrying variant (TA)₇ and hyperbilirubinemia (P < 0.05). We demonstrated the association of two genotypes with gallstones formation among SCA children patients: (TA)₇/(TA)₇ and (TA)₇/(TA)₈ with P = 8.1 × 10⁻⁸ and P = 0.01, respectively. (TA)₇ and (TA)₈ allele variants act as a risk factor for early gallstones formation in SCA patients with P = 5.8 × 10⁻⁹ and P = 0.01, respectively. As for the control group only the genotype (TA)₇/(TA)₇ presented a risk factor for gallstones formation. Conclusion. The novelty of this report is that it is the first time that a similar study was made on the Tunisian children sickle cell population and that the results show a clear association of (TA)₇ variant in early gallstones formation in Tunisian SCA children. Interestingly our findings highlighted the association of (TA)₈ variant as well, which was not found in previous studies.