Prenatal diagnosis of hemoglobinopathies in Tunisia: an 18 years of experience.

UNLABELLED: Hemoglobinopathies are the most common genetic disease in Tunisia with a total carrier prevalence of 4.48%. OBJECTIVE: The aim of this study was to report an 18-year fully achieved experience of prenatal diagnosis (PND) of hemoglobinopathies (1994-2012) and to assess the impact of this prevention program. PATIENT AND METHODS: A total of 461 fetuses of 340 at-risk couples have been the subject of PND for beta-thalassemia major risk (41%), for sickle cell anemia risk (40.3%), for S/beta-thal risk (14.7%). The remainder fetuses were at risk for a compound heterozygote hemoglobinopathies (S/O, O/beta-thal, S/C….). Fetal DNA was studied by PCR procedure including the reverse dot-blot technique and the amplification refractory mutation system and direct sequencing. RESULTS AND DISCUSSION: Only 13.8% of the fetal samplings were conducted by chorionic villus sampling. The molecular result for beta-thalassemia risk has shown 13 beta-thal mutations, with two common: codon 39 (C>T) and IVS1-110 (G>A). The last 3 years, STR study has permitted to reduce the problems of maternal cell contamination. Among the 461 tested fetuses, 121 were affected, and then the pregnancy was terminated except for 13 cases, because of religious considerations and this despite the abortion legality in Tunisia. The conducted PND is only about 30 PND per year corresponding essentially to the couples living in Tunis City and surrounding area. PND number has increased from 1994 to 2009. This evolution has brutally decreased after the Tunisian revolution (2010). CONCLUSION: Although the good running of the PND, it covers only the Tunis city with low impact because it prevent apparition of only a mean of 7.3% of new cases. The reduced number of PND is not a technical inconvenience but rather a lack of a preventive program.

Association of TGFB1 -509C/T polymorphism gene with clinical variability in cystic fibrosis patients: A case-control study.

PURPOSE: In this work, we are interested to study the implication of -509C/T polymorphism, located in the promoter region of TGFB1 (transforming growth factor ß1), in the phenotypic variability of CF patients. PATIENTS AND METHODS: The present study enrolled 111 CF patients and 100 healthy control subjects. The study of the -509C/T polymorphism was performed using PCR-RFLP method. RESULTS: We found that patients carried non-F508del homozygous mutation with TT genotype was associated to lung symptoms (P=0.04). This association was not found in the sub-groups of patients with F508del at homozygous state P=0.145. No association was found between this polymorphism and the variability of digestive, pancreatic and ileus meconial symptoms. CONCLUSION: On the basis of our results, the -509C/T polymorphism of the TGFB1 gene seems to be a modulator factor of cystic fibrosis.

Prenatal diagnosis of cystic fibrosis: 10-years experience.

PURPOSE: We present in this study our 10years experience in prenatal diagnosis of cystic fibrosis performed in the Tunisian population. PATIENTS AND METHODS: Based on family history, 40 Tunisian couples were selected for prenatal diagnosis. Fetal DNA was isolated from amniotic fluid collected by transabdominal amniocentesis or from chronic villi by transcervical chorionic villus sampling. The genetic analysis for cystic fibrosis mutations was performed by denaturant gradient gel electrophoresis and denaturing high-pressure liquid phase chromatography. We performed microsatellites analysis by capillary electrophoresis in order to verify the absence of maternal cell contamination. RESULTS: Thirteen fetuses were affected, 21 were heterozygous carriers and 15 were healthy with two normal alleles of CFTR gene. Ten couples opted for therapeutic abortion. The microsatellites genotyping showed the absence of contamination of the fetal DNA by maternal DNA in 93.75%. CONCLUSION: Our diagnostic strategy provides rapid and reliable prenatal diagnosis at risk families of cystic fibrosis.

Association between clinical expression and molecular heterogeneity in ß-thalassemia Tunisian patients.

Beta-thalassemia is the most frequent hereditary blood disorder in Tunisia because of its geographic localization and history. This pathology is characterized by a complex multisystem process with genetic and biochemical interactions. The aim of this work was to establish phenotype/genotype association through studying the distribution and the relationship between ß-thalassemia and α-thalassemia mutations and three polymorphic markers: the C → T polymorphism at -158 of the Gγ gene, the RFLP haplotype and the repeated sequence (AT)xTy in the ß globin silencer, in two groups of ß-thalassemia major and ß-thalassemia intermedia (TI) patients. Statistical analysis has shown that moderate expression seen in TI patients was significantly associated to ß(+) -87 (C → G), -30 (T → A) and IVSI-6 (T → C) mutations, haplotypes VIII, IX and Nb and to XmnI polymorphism. The regression analysis of combined genotypes (mutation/XmnI/RFLP haplotype) revealed that they contribute to justify 17.1 % of clinical expression diversity (p < 0.05). Among the studied genotypes the XmnI polymorphism seems to be the most determinant modulating factor, followed by the ß-thalassemia mutation and RFLP haplotype. Our findings highlight the heterogeneity of molecular background of ß-thalassemia that would be responsible of clinical variability.