The human α-globin genes are paralogues, sharing a high degree of DNA sequence similarity and producing an identical α-globin chain. Over half of the α-globin structural variants reported to date are only characterized at the amino acid level. It is likely that a fraction of these variants, with phenotypes differing from one observation to another, may be due to the same mutation but on a different α-globin gene. There have been very few previous examples of hemoglobin variants that can be found at both HBA1 and HBA2 genes. Here, we report the results of a systematic multicenter study in a large multiethnic population to identify such variants and to analyze their differences from a functional and evolutionary perspective. We identified 14 different Hb variants resulting from identical mutations on either one of the two human α-globin paralogue genes. We also showed that the average percentage of hemoglobin variants due to a HBA2 gene mutation (α2) is higher than the percentage of hemoglobin variants due to the same HBA1 gene mutation (α1) and that the α2/α1 ratio varied between variants. These α-globin chain variants have most likely occurred via recurrent mutations, gene conversion events, or both. Based on these data, we propose a nomenclature for hemoglobin variants that fall into this category.

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Annals of Hematology
Erasmus MC: University Medical Center Rotterdam

Moradkhani, K, Prehu, C, Old, J, Henderson, S, Balamitsa, V, Luo, H-Y, … Patrinos, G.P. (2009). Mutations in the paralogous human α-globin genes yielding identical hemoglobin variants. Annals of Hematology, 88(6), 535–543. doi:10.1007/s00277-008-0624-3