Hb Bab-Saadoun or alpha 2 beta (2)48(CD7)Leu----Pro, a mildly unstable variant found in an Arabian boy from Tunisia

A new β⁰-thalassemia frameshift mutation [β 48 (-T)] in a Uruguayan family

We describe here a new frameshift mutation of β-thalassemia in a Uruguayan family with Italian ancestry [β48 (-T); HBB:c.146delT]. This frameshift results in formation of premature stop codon (TGA) 40 bp downstream and in a short unstable product that is degraded in the cell.

Sickle cell disease in Middle East Arab countries

The sickle cell (HbS) gene occurs at a variable frequency in the Middle Eastern Arab countries, with characteristic distribution patterns and representing an overall picture of blood genetic disorders in the region. The origin of the gene has been debated, but studies using β-globin gene haplotypes have ascertained that there were multiple origins for HbS. In some regions the HbS gene is common and exhibits polymorphism, while the reverse is true in others. A common causative factor for the high prevalence and maintenance of HbS and thalassaemia genes is malaria endemicity. The HbS gene also co-exists with other haemoglobin variants and thalassaemia genes and the resulting clinical state is referred to as sickle cell disease (SCD). In the Middle Eastern Arab countries, the clinical picture of SCD expresses two distinct forms, the benign and the severe forms, which are related to two distinct β-globin gene haplotypes. These are referred to as the Saudi-Indian and the Benin haplotypes, respectively. In a majority of the Middle Eastern Arab countries the HbS is linked to the Saudi-Indian haplotype, while in others it is linked to the Benin haplotype. This review outlines the frequency, distribution, clinical feature, management and prevention as well as gene interactions of the HbS genes with other haemoglobin disorders in the Middle Eastern Arab countries.

Hemoglobin H disease due to a de novo mutation at the α2-globin gene and an inherited common α-thalassemia deletion found in a Chinese boy

Hemoglobin (Hb) H disease is a moderate form of α-thalassemia resulting from various genetic defects. A novel frameshift mutation cd 43/44(-C) at the α2-globin gene was identified in a Chinese boy with hemoglobin H disease by sequencing. The proband's mother carries a common α-thalassemia deletion while his father was normal both in the hematological phenotype and α-globin genotype, which suggested that it occurred as a de novo mutation. Molecular studies revealed a compound heterozygote for the Southeast Asian α-thalassemia deletion and this novel spontaneous mutation (-/α(T)α) and the patient exhibited the clinical manifestation of classic hemoglobin H disease. Based on the results of excluding the possibility of a somatic mosaicism of a point mutation in the α2-globin gene, we progress that this de novo single-base deletion should have arisen during the spermatogenic process or earlier embryonic stage. The present study provides information in determining a supplementary model of inheritance for α-thalassemia, which should be useful in genetic counseling.

Clinical and molecular aspects of haemoglobinopathies in Tunisia

BACKGROUND

For the last two decades, studies on the population genetics of Tunisians have focused on variations of protein and genetic markers. Results confirmed the genetic heterogeneity of Tunisians caused by the admixtures with migratory human groups arriving mainly from Africa, Europe, and Asia. These studies also allowed the screening of rare mutants and many haemoglobin variants.

METHODS

The present study delineates the incidence of the different haemoglobinopathies in Tunisia. Previously collected data and results obtained from epidemiological and clinical studies of 1238 blood donors and 276 patients were compared. The chromosomal backgrounds of different haemoglobinopathies were explored by molecular techniques (denaturing gradient gel electrophoresis (DGGE), amplification refractory mutation system (ARMS) polymerase chain reaction (PCR), and sequencing).

RESULTS

This study indicates that appropriate DNA methodologies required for a nationwide preventive program in Tunisia are available and that prenatal diagnosis is feasible. Additionally, analysis of sequence polymorphisms allowed a better understanding of the gene recombination events and their application for tracing back the origin and the diffusion of the mutations.

CONCLUSIONS

Molecular analysis techniques such as DGGE and ARMS PCR are socially and economically the most suitable techniques to be used in Tunisia for the detection and the identification of haemoglobin abnormalities. At present, their use is essential to conduct a clear and efficient screening program.

Three sickle cell anemia patients each with a different alpha chain variant. Diagnostic complications

We have studied three sickle cell anemia patients who also carried a heterozygosity for one of the following alpha chain abnormalities: Hb G-Philadelphia [alpha 68(E17)Asn-->Lys], Hb Montgomery [alpha 48 (CE6)Leu-->Arg], and Hb Chicago [alpha 136(H19)Leu-->Met]. Electrophoretic analyses alone may result in incomplete and incorrect information. Confirmation of the diagnosis of Hb SS or Hb SC disease by one of the fast high performance liquid chromatographic procedures is recommended.