Multiplex Minisequencing of the HBB Gene: A Rapid Strategy to Confirm the Most Frequent ß-Thalassemia Mutations in the Tunisian Population.

The ß hemoglobinopathies [ß-thalassemia (ß-thal) and structural hemoglobin (Hb) variants such as Hb S (HBB: c.20A > T) and Hb E (HBB: c.79G > A)] are among the most common inherited diseases worldwide. In Tunisia, due to the high prevalence of consanguineous marriages, the recurrent risk of this disease is high. The average prevalence of hemoglobinopathies is 4.48%, reaching 12.50% in some focus regions. The molecular investigations on thalassemia contributed to establishing the spectrum of mutations in the Tunisian population. The total number of HBB gene mutations identified was 24. The two most frequent mutations, codon 39 (C > T) (HBB: c.118C > T) and IVS-I-110 (G > A) (HBB: c.93-21G > A) accounted for 70.0% of the total encountered ß-thal cases. These two mutations together with IVS-I-2 (T > G) (HBB: c.92 + 2T > G) and the Hb S variant account for more than 90.0% of all HBB genetic variants in Tunisia. Thus, developing rapid, inexpensive and reliable mutation-specific molecular diagnostic assays targeting our Tunisian populations is our aim to facilitate routine detection of hemoglobinopathies. In this report, we describe the successful application of the multiplex minisequencing assay as an alternative strategy for genetic diagnosis of HBB gene disorders in Tunisia.

Genetic study in a tunisian family revealed IVS1+1G>A mutation in the CHM gene.

Choroideremia is a rare X-linked recessive, hereditary retinal pigment epithelial dystrophy, characterized by night blindness and progressive constriction of the visual fields leading to blindness in young adulthood. In this study, we reported three cases of choroideremia belonging to a Tunisian family. Patients complained of vision loss and night blindness. Fundus examination revealed diffused chorioretenal atrophy. In all cases, there was a visual field constriction and an undetectable electroretinography. Direct sequencing of the CHM gene detected a guanine to adenine transition (G>A) into the donor splice site of intron 1 leads to aberrantly spliced mRNA producing a premature stop codon and therefore functional loss of the CHM gene product, REP-1. The diagnosis should be considered in patients with a suitable family history and fundus findings.