Synthetic review on the different anthropological aspects of hemoglobinopathies in Tunisia

Abstract

Hemoglobinopathies are a group of hereditary hemolytic anemia characterized by qualitative (sickle cell disease) or quantitative (thalassemia) defects in the alpha or beta-globin chain synthesis. Homozygotes or compound heterozygotes for the mutated alpha or beta-globin genes can cause severe anemia at an early age. These pathologies are common in some areas (Mediterranean, Africa, India, and Southeast Asia). Tunisia, by its geographical location, its history and its socio-economic system, is particularly concerned by these pathologies. The frequency and severity of the beta-thalassemia syndrome justify the establishment of prevention programs including screening and genetic counseling especially in regions with relatively high degree of consanguinity. Molecular investigations are conducted to identify the molecular defects involved in β-thalassemia. Determination of the spectrum and distribution of beta globin gene mutations and haplotypes associated gave us the opportunity to develop and improve diagnostic tests and eventually to offer ante-natal diagnosis. In addition, molecular analyses gave us important anthropological information about the origins and the spread of Hemoglobinopathies mutations. Investigations have been conducted to propose the origin and the migration schemes of the most frequent β-thalassemia mutations in Tunisia (codon 39 and IVSI 110): a west-Mediterranean and ancient origin for codon 39 and an east-Mediterranean origin (Anatolia) for IVSI 110 during the Neolithic period. Concerning the βS mutation of the sickle cell anemia, the β-globin cluster restriction enzyme haplotypes and the sequence polymorphism analyses show a multicentric origin for this mutation. Arose about 3,000 years ago, this mutation was very likely introduced in North Africa from sub-Saharan Africa.

Key words: Hemoglobinopathies, Genetic counseling, Molecular analyses,
Migration schemes, Origins of mutations.