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.

Rare hemoglobin variants in Tunisian population.

During the last 30 years, many studies concerning hemoglobinopathies were realized among Tunisians. More than twenty different thalassemic alleles were detected on the ß-globin gene, and less are affecting the α-globin genes. Unusual hemoglobin (Hb) variants other than Hb S, Hb C, and Hb O-arab, which are the most frequent variants in Tunisia, were also detected. Eight Tunisian subjects were studied at phenotypic and molecular levels. Hematological indices and hemoglobin (Hb) pattern were performed by alkaline electrophoresis and isoelectric focusing (IEF),and the Hb fractions were quantitated by cation exchange HPLC. On genomic level, coding regions were amplified by polymerase chain reaction (PCR) followed by a sequencing of the purified PCR products using the dye terminator method. Seven uncommon Hb variants were detected and described for the first time among Tunisians. HbA2-Tunis [δ46(CD5), Gly → Glu, GGG → GAG] is the newly described δ-chain variant in our laboratory, and some other variants (Hb Constant Spring, G San Jose, and Hb J-Bangkok) are very uncommon in the Mediterranean region. We present here an updated review of the Hb variants detected among Tunisians. Twenty-one rare Hb variants were detected affecting the α1-, α2-, δ-, γ-, and ß-globin genes, leading in some cases to a severe phenotype especially when the stability is completely altered. The ethnical history of Tunisia could explain this important variability of the observed rare Hb variants.

[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.