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.

Coinheritance of HbO Arab/ß0-thalassemia with Severe Manifestation in Newborn.

OBJECTIVE: In this study, we report a Tunisian newborn boy referred for neonatal hemolytic anemia with yellowish skin and enlarged spleen due to coinheritance of hemoglobin O (HbO) Arab and ß-thalassemia. STUDY DESIGN: Hematological parameters were collected using an automated blood cell counter. The amounts of Hb fractions were measured by capillary electrophoresis of Hb. Amplification and sequencing of the HBB gene were performed by Sanger's method. RESULTS: Family study and genetic analysis revealed that the proband was a carrier of two hemoglobinopathies: HbO Arab and ß0-thalassemia. CONCLUSION: The coexistence of these two pathologies complicated the general state of the newborn boy and led to a severe anemia at birth. KEY POINTS: · Severe neonatal anemia can be caused by hemoglobinopathy.. · Coinheritance of HbO Arab/ß0-thalassemia complicated the general state of the newborn.. · Diagnosing hemoglobinopathy at an early age improves patient care..

New Deletion at Promoter of HBG1 Gene in Sickle Cell Disease Patients With High HbF Level.

OBJECTIVES: The 5' upstream region of the HBG1 gene plays a very important role in the expression of fetal hemoglobin (HbF). In contrast, increased HbF levels can inhibit the deoxygenation-induced polymerization of sickle hemoglobin (α2ßS2), which leads to moderation at the clinical level among sickle cell disease (SCD) patients. Thus, we focused on this article on the study of the 5' upstream region of HBG1 among SCD pediatric patients with high levels of HbF. MATERIALS AND METHODS: Fifteen SCD pediatric patients were chosen during the first time of diagnosis, and the HbF values were determined before hydoxyurea treatment. The ages at entry ranged from 1 to 8 years. The mutational screening of the 5' upstream region of the HBG1, which extends to -587 bp, was performed by polymerase chain reaction/sequencing. RESULTS: HbF values range from 6.9% to 26%. Sequencing results showed the presence of 6 known polymorphisms, which are as follows: RS35993903, RS34844625, RS3020750, RS2860456, RS2860470, and RS12290216. Interestingly, we also found a new deletion of GCAG in the HBG1 promoter at position -273. CONCLUSIONS: We described a new mutation, which is a deletion of GCAG in the HBG1 promoter at position -273. This deletion could affect a binding site of a transcription factor unknown so far and thus modulate the expression of the HBG1 gene.

The role of rs1984112_G at CD36 gene in increasing reticulocyte level among sickle cell disease patients.

AIMS AND BACKGROUND: Mediators of adhesion become a potential new target for pharmacological therapy to struggle the complications of sickle cell disease (SCD). Several mechanisms for increased adherence have been postulated and the well-studied are CD36 and VLA4 which encoded by ITGA4. Herein, we sought to determine whether one polymorphism of CD36 namely: rs1984112 and three exons of ITGA4 (4, 5, and 6) are implicated in hemolytic status and clinical events among SCD Tunisian patients. MATERIAL AND METHODS: This study enrolled 99 unrelated Tunisian subjects (63SS and 36Sß). All SCD patients are children (less than 16 years old). The rs1984112 and the ITGA4's exons 4, 5, and 6 were analyzed for all subjects by PCR/sequencing. The association of each genotype found with both clinical complications and hemolytic status was performed using t-test. Clinical events studied included vaso-occlusive crisis (VOC), osteonecrosis, stroke, frequent infection, priapism, and acute syndrome. RESULTS: The results show that rs1984112_G allele at CD36 gene revealed to be associated with higher levels of reticulocyte count (p < 0.01). The statistical result show a near significance of homozygous mutant GG genotype with VOC (p = 0.051). No association between rs1984112_G allele and the clinical severity of SCD were found. Mutational screening of exon 4, 5, and 6 of ITGA4 gene revealed absence of mutated variant. CONCLUSION: Our results are similar to those found in Portuguese population which reported the role of rs1984112_G in increasing reticulocyte level among SCD patients. Consequently, the rs1984112_G of CD36 could be considered as a reliable biomarker for predicting patients at high risk for vascular occlusions and thus, allows earlier and more effective therapeutic management.

rs11886868 and rs4671393 of BCL11A associated with HbF level variation and modulate clinical events among sickle cell anemia patients.

AIMS: Fetal hemoglobin (HbF) modulates the phenotype of sickle cell anemia (SCA) by inhibiting deoxy sickle hemoglobin (HbS) polymerization. HbF genes are genetically regulated, and the level of HbF and its distribution among sickle erythrocytes is highly variable. Herein, we aimed to determine whether two functional polymorphisms of BCL11A are implicated in the variation of HbF and clinical events in SCA Tunisian patients. MATERIAL AND METHODS: The studied population consisted of 148 SCA patients with SS phenotype. The group of patients was divided into two subgroups according to the threshold point of %HbF which is 15%. Genotyping of rs11886868 and rs4671393 was performed using PCR/Sequencing. To test for trait association with the candidate SNPs, genotype and allele frequencies between 'group who had %HbF < 15' and 'group who had %HbF >15' (controls) were compared using Pearson's chi-square test (compare 2, version 1.02). The association of each genotype and the combined genotype with complications was performed by logistic regression test. RESULTS: Our findings showed that the majority of patients carried genotype CT of rs11886868 and genotypes AG and GG of rs4671393 present HbF level < 15%. RR = 0.08, RR = 0.176, and RR = 0.189, respectively. The results showed a significant association between the alleles T of rs11886868 and G of rs4671393 and %HbF < 15% with P = 0.016; RR = 0.39 and P = 8.9 × 10(-3): RR = 0.567, respectively. Interestingly, the C allele of the rs11886868 and the A allele of the rs46713939 were associated with an ameliorated phenotype in patient's SCA. The combination of the genotypes GG and CT explains more phenotypic variance than the sum of the two BCL11A SNPs taken individually.

rs11886868 and rs4671393 of BCL11A associated with HbF level variation and modulate clinical events among sickle cell anemia patients.

AIMS: Fetal hemoglobin (HbF) modulates the phenotype of sickle cell anemia (SCA) by inhibiting deoxy sickle hemoglobin (HbS) polymerization. HbF genes are genetically regulated, and the level of HbF and its distribution among sickle erythrocytes is highly variable. Herein, we aimed to determine whether two functional polymorphisms of BCL11A are implicated in the variation of HbF and clinical events in SCA Tunisian patients. MATERIAL AND METHODS: The studied population consisted of 148 SCA patients with SS phenotype. The group of patients was divided into two subgroups according to the threshold point of %HbF which is 15%. Genotyping of rs11886868 and rs4671393 was performed using PCR/Sequencing. To test for trait association with the candidate SNPs, genotype and allele frequencies between 'group who had %HbF < 15' and 'group who had %HbF >15' (controls) were compared using Pearson's chi-square test (compare 2, version 1.02). The association of each genotype and the combined genotype with complications was performed by logistic regression test. RESULTS: Our findings showed that the majority of patients carried genotype CT of rs11886868 and genotypes AG and GG of rs4671393 present HbF level < 15%. RR = 0.08, RR = 0.176, and RR = 0.189, respectively. The results showed a significant association between the alleles T of rs11886868 and G of rs4671393 and %HbF < 15% with P = 0.016; RR = 0.39 and P = 8.9 × 10-3: RR = 0.567, respectively. Interestingly, the C allele of the rs11886868 and the A allele of the rs46713939 were associated with an ameliorated phenotype in patient's SCA. The combination of the genotypes GG and CT explains more phenotypic variance than the sum of the two BCL11A SNPs taken individually.

Gilbert syndrome acts as a risk factor of developing gallstone among ß hemoglobinopathy Tunisian patients.

BACKGROUND: As a result of chronic hemolysis, hyperbilirubinemia is often observed, leading to the formation of pigment cholelithiasis which could be busted by the presence of uridine diphosphoglucuronosyltransferase 1A1 defects. AIM: Herein, we investigated the effect of glibert mutation on the occurrence of pigment cholelithiasis in Tunisian patients with beta (ß) hemoglobinopathy including sickle cell anemia and ß thalassemia (minor). SUBJECTS AND METHODS: Our study included 151 subjects divided in 75 SCA patients and 76 ß thalassemia patients. Both groups of patients were divided into two sub-groups according to the presence or absence of cholelithiasis. The relationship between A(TA)nTAA variation of UGT1A1 gene, the serum bilirubin level and the occurrence of cholilithiasis was investigated. RESULTS: Our results show a significant association between genotypes carrying variant (TA)7 and hyperbilirubinemia (p<0.05). Furthermore, we demonstrated a significant association between (TA)6/(TA)7 and (TA)7/(TA)7 genotypes with cholelithiasis among sickle cell anemia and thalassemia patients (p<0.05). CONCLUSION: Altogether, our data provide evidence that genotypes (TA)6/(TA)7 and (TA)7/(TA)7 and (TA)7 variant present a risk factor of developing gallstone among ß hemoglobinopathy Tunisian patients.

Association between rs267196 and rs267201 of BMP6 gene and osteonecrosis among sickle cell aneamia patients.

AIMS: The skeletal manifestations of sickle cell disease are the result of changes in bone and bone marrow caused by chronic tissue hypoxia that is exacerbated by episodic occlusion of the microcirculation by the abnormal sickle cells. Furthermore, the occurrence of osteonecrosis is under the control of some modifier gene. BMP6 (Bone morphogenetic protein) has been reported as associated with osteonecrosis in sickle cell anemia (SCA). Herein, we intend to study the impact of rs267196, rs267201, rs408505 and rs449853 of BMP6 gene in the occurrence of osteonecrosis among sickle cell patients in Tunisia. METHODS: Our study involved 100 SCA patients among whom 19 have osteonecrosis of the head of the femur. The latter polymorphisms of BMP6 gene were analyzed for all subjects by PCR/sequencing. To test for trait association with the candidate SNPs, genotype and allele frequencies between cases (osteonecrosis group) and controls (non-osteonecrosis group) were compared using Pearson's chi_square test with a significance threshold of P<0.05 (compare 2, version 1.02). RESULTS: Our findings showed that the patients carried genotype TA of rs 267196 and genotype AG of rs267201 present a high risk factor for developing osteonecrosis RR=1.317 and RR=1.3 respectively. The results showed a significant association between the alleles A of rs 267196 and G of rs267201 and osteonecrosis P=0.0023; RR=2.42 and P=0.041; RR=2.24 respectively. Interestingly, SCA patients with the combined genotype TA/AG were found to be at higher risk of developing osteonecrosis (P=0.009). As for rs408505 and rs449853 of BMP6 gene no significant association was found among SCA patients.

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.

Early complication in Sickle Cell Anemia children due to A(TA)_n TAA 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)_{n} TAA at the UGT1A1 promoter and the relationships between the various A(TA)_{n} TAA 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 carried 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.