Molecular basis of pyruvate kinase deficiency among Tunisians: description of new mutations affecting coding and noncoding regions in the PKLR gene.

INTRODUCTION: Pyruvate kinase (PK) deficiency is one of the most common hereditary nonspherocytic hemolytic anemias worldwide with clinical manifestations ranging from mild to severe hemolysis. However, investigation of this enzymopathy is lacking in Tunisia. We report here a pioneer investigation of PK deficiency among Tunisian cases referred to our laboratory for biological analysis of unknown cause of hemolytic anemia. METHODS: Two hundred and fifty-three patients with unknown cause of hemolytic anemia have been addressed to our laboratory in order to investigate for red blood cells genetic disorders. Red cell enzyme activities were measured by standard methods, and molecular analysis was performed by DNA sequencing. The interpretation of mutation effect and the molecular modeling were performed by using specific software. RESULTS: Six different PKLR mutations were found (c.966-1G>T; c.965+1G>A; c.721G>T; c.1163C>A; c.1456C>T; c.1537T>A), among which four are described for the first time. Genotype-phenotype correlations for the novel missense mutations were investigated by three-dimensional structure analysis. CONCLUSION: This study provides important data of PK deficiency among Tunisians. It might be followed by a large neonatal screening to determine the spectrum of PK mutations and identify potential deficient patients for an early medical follow-up.

Frequency of three polymorphisms of the CCL5 gene (rs2107538, rs2280788 and rs2280789) and their implications for the phenotypic expression of sickle cell anemia in Tunisia.

The pro-inflammatory context of sickle cell disease promotes the liberation of cytokines such as CCL5, encoded by a gene located on chromosome 17. Herein, the occurrence of three variations of CCL5 in sickle cell anemia (SCA) and their relations to two major complications - painful crisis and presence of infections - were investigated. 100 SCA Tunisian patients and 100 healthy subjects were included in the case control study. Then the sample of patients was divided into two groups according to the presence or absence of each complication. The polymorphisms, namely g.-403G>A, g.-28C>G and g.In1.+1T>C, were analyzed by PCR/sequencing. Our findings show the presence of eight genotypes, namely GG, GA and AA of g.-403G>A, CC, CG and GG of g.-28C>G, and TT and TC of g.In1.+1T>C. The frequencies of studied single nucleotide polymorphisms (SNPs) and haplotypes in SCA patients do not differ significantly from healthy control group results. There is also no significant association between the analyzed polymorphisms and complications as for painful crisis and presence of infections (p > 0.05). Altogether, our data support the conclusion that the three polymorphisms of CCL5, namely g.-403G>A, g.-28C>G and g.In1.+1T>C, do not seem to be involved in the clinical variability of SCA in Tunisia.

Association of IL-12p40 +1188 A/C polymorphism with nasopharyngeal cancer risk and tumor extension.

The interleukin 12 (IL-12) cytokine, encoded by polymorphic genes, plays a central role in the T helper 1 cell-mediated immunity against tumors. We investigated whether the 3' untranslated region +1188 A/C polymorphism (rs 3212227) influences the nasopharyngeal carcinoma (NPC) risk in Tunisian patients. DNA analysis of 247 patients and 284 healthy individuals showed a higher frequency of the 1188 C allele and the CC genotype in patients than in controls (P = 0.00001 and P = 0.00005) suggesting that the C variant allele is associated with the susceptibility to NPC. Additional testing showed that the homozygous CC genotype is also associated with advanced stage of the tumor extension at presentation (P = 0.022). Our data suggest that the impaired production of IL-12 behaves as a risk factor for NPC occurrence and progression.

[Polymorphisms of the UDP-glucuronosyltransferase 1-A1 gene in Tunisian population]. / Polymorphismes alleliques du gene UDP-glucuronosyltransferase 1A1 dans une population Tunisienne.

The UDP-glucuronosyltransferase 1A1 gene that encode the enzyme UGT1A1 responsible for glucuronidation undergoes several variations that may affect the enzymatic activity or expression and which are the cause of metabolic disorders related to the glucuronidation of bilirubin, such as Gilbert's syndrome and Crigler Najjar's syndrome. Among the most common variations, there is the repeat polymorphism A (TA) n TAA in TATA box and biallelic mutation G211A in exon 1. We consider in this work to determine their frequencies in a healthy population. The polymorphism A (TA) n TAA showed that genotype [TA7/TA7] was described as being associated with Gilbert's syndrome and was encountered in 11% of the population studied. This percentage is close to the value described in the Caucasian population, estimated at 10%. Concerning the polymorphism G211A, our results show that the mutated allele is encountered in 15.7% of our study population. This frequency differs greatly from that reported for Caucasians and Afro-Americans but it is similar to that perceived at the Japanese. All these results suggest that the Tunisian population appears to be heterogeneous view UGT1A1 gene mutation status. Regarding the origins and distribution of such polymorphisms in our population, the study reveals a high haplotypic haplotype (TA) 6-G considered ancestral. The comparison of the haplotype structure generally leads to the development of a hypothetical tree of the origin and spread of different haplotypes.