Abstract
Hemoglobin (Hb) Grey Lynn is a Hb variant caused by a substitution of Phe for Leu at position 91 of α1-globin chain, originally described in individual of unknown ethnic background. This article addresses the interaction of Hb Grey Lynn with a non-deletional α+-thalassemia found in Thailand, a hitherto un-described condition. The proband was adult Thai woman referred for investigation of mild anemia with Hb 90 g/L. Hb analyses using low pressure liquid chromatography raised a suspicion of abnormal Hb presence, which was failed to demonstrate by cellulose acetate electrophoresis and capillary electrophoresis. DNA sequencing identified a CTT (Leu) to TTT (Phe) mutation at codon 91 corresponding to the Hb Grey Lynn (Vientiane) [α91(FG3)Leu>Phe (α1) on α1-globin gene and a C deletion between codons 36 and 37 on α2-globin gene causing α+-thalassemia. As compared to those observed in a compound heterozygote for Hb Grey Lynn / α0-thalassemia reported previously, higher MCV (81.7 fL) and MCH (26.3 pg) values with a lower level of Hb Grey Lynn (19.7%) were observed in the proband. The normochromic normocytic anemia observed could be due to the interaction of Hb Grey Lynn with α+-thalassemia. The two mutations could be identified using PCR-RFLP and allele-specific PCR assays developed.
Highlights
The human globin genes are organized into two separated clusters, alpha (α) located on chromosome 16 and beta (β), on chromosome 11
We have reported for the first time the interaction of Hb Grey Lynn (Vientiane) [α91(FG3)Leu>Phe (α1)] with a rare α+-thalassemia point mutation [α2 codon 36/37 (-C)] in adult Thai individual
Initial Hb analysis on cellulose acetate electrophoresis identified no abnormal Hb (Figure 1A), analysis using low performance liquid chromatography (LPLC) analyzer identified 63.6 % Hb A, 3.1 % Hb A2 and 19.7 % unknown Hb separating between Hb A and Hb A2 at the Hb E-window, quite resembling Hb E heterozygote (Figure 1B)
Summary
The human globin genes are organized into two separated clusters, alpha (α) located on chromosome 16 and beta (β), on chromosome 11. The structure of α- cluster is 5’-ζ-ψζ-ψα2-ψα1-α2-α1θ-3’, with a regulatory element located upstream of the embryonic ζ-gene. For the β-cluster the order is 5’-ε-Gγ-Aγ-ψβ-δ-β-3’ with the locus control region located upstream of the ε-globin gene [1]. Inherited Hb disorders with absent or reduced synthesis of particular globin chains are called thalassemias, while Hb variants or abnormal Hbs are structurally inherited changes of globin chains. Both Hb variants and thalassemias have been increasingly reported worldwide. The HbVar database has noted more than 1,150 mutations [3]
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