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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 byITGA4. Herein, we sought to determine whether one polymorphism ofCD36namely: rs1984112 and three exons ofITGA4(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 36Sβ). All SCD patients are children (less than 16 years old). The rs1984112 and theITGA4’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 usingt-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 atCD36gene 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 ofITGA4gene 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 ofCD36could be considered as a reliable biomarker for predicting patients at high risk for vascular occlusions and thus, allows earlier and more effective therapeutic management. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The diversity of sickle cell disease severity is attributed to several cis acting factors, among them the single nucleotide polymorphisms (SNPs) and (AT) rich region in the β-locus control region (β-LCR). This contains five DNase I hypersensitive sites (HS) located 6 to 22 kb upstream to the ε gene. The most important of these is the HS2 (5′ β-LCR-HS2), characterized by the presence of three different SNPs and a microsatellite region known to be in association with βS chromosomes in various populations. The aim of this study was to present the molecular investigation of the 5′ β-LCR-HS2 site in normal and sickle cell disease individuals in order to determine if there is any correlation or specificity between these molecular markers, the βS Tunisian chromosomes and phenotypical expression of sickle cell disease. One hundred and twenty-four chromosomes from Tunisian individuals (49 βS carriers and 13 normal individuals) were screened by polymerase chain reaction (PCR) and sequencing for the polymorphic short tandem microsatellite repeats (AT)XN12(AT)Y and the three SNPs (rs7119428, rs9736333 and rs60240093) of the 5′ β-LCR-HS2. Twelve configurations of the microsatellite motif were found with an ancestral configuration elaborated by ClustalW software. Normal and mutated alleles were observed at the homozygous and heterozygous states for the three SNPs. Correlation between microsatellites and SNPs suggests that mutant SNP alleles were mainly associated, in the homozygous sickle cell disease phenotype, with the (AT)8N12GT(AT)7 configuration, whereas, normal SNP alleles were associated with the (AT)XN12(AT)11 configurations in normal βA chromosomes. The correlation of these various configurations with Hb F expression was also investigated. The principal component analysis (PCA) showed the correlation between the homozygous sickle cell disease phenotype, mutated SNP alleles and the Benin microsatellite configuration (AT)8N12GT(AT)7, which confirmed the specificity of this configuration to the βS chromosomes. In addition, the observed high level of Hb F (14.6%) could play a protective role against Hb S to justify the modulation of sickle cell disease severity within the Benin haplotype compared to the other haplotypes. This study highlights the fact that the β-LCR-HS2 could be a genetic marker to identify the ethnic Tunisian βS chromosomes and facilitate the molecular diagnosis of sickle cell disease. [ABSTRACT FROM AUTHOR]

We describe a new δ-globin variant, Hb A2-Pasteur-Tunis [δ59(E3)Ly(s)→Asn, AAG→AAC]. This hemoglobin (Hb) displayed an electrophoretic mobility faster than normal Hb A2 and was expressed at 2.2 %. The molecular defect was characterized by DNA sequencing and confirmed by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-designed protocol. Hb A2-Pasteur-Tunis was found in a carrier of a codon 39 ((C)→T) β0-thalassemia (thal), presenting with a normal Hb A2 level. Phenotype and genotype investigations revealed that the total Hb A2 level of the patient was that expected for a minor β-thal (4.8%). [ABSTRACT FROM AUTHOR]

We describe a new δ-globin variant, Hb A2-Tunis [δ46(CD5)Gly → Glu; HBD: c.140G>A]. This hemoglobin (Hb) variant displayed a faster electrophoretic mobility than normal Hb A2 and was expressed at 3.2%. The molecular defect was characterized by DNA sequencing analysis. Hb A2-Tunis was found in a carrier of a β0-thalassemia (β0-thal) [IVS I-1 (β143, G>A); HBB: c.92 + 1G>A] and Hb C [β6(A3)Glu → Lys; HBB: c.19G>A], presenting with a normal Hb A2 level. Phenotype and genotype investigations revealed that the patient has a total Hb A2 level of 7.1% that was expected for a β-thalassemia (β-thal) minor carrier. [ABSTRACT FROM AUTHOR]