Abstract
Alpha hemoglobin stabilizing protein (AHSP) is an erythroid protein that binds specifically to the alpha globin chains to form a stable complex, preventing their precipitation before the assembly of the hemoglobin tetramere. Studies have shown that
AHSP is required for normal erythropoiesis,
knock-out mice has a phenotype similar to beta thalassemia,
loss of AHSP worsens the severity of the disease in thalassemic mice.
Therefore, altered AHSP expression or function could account for some of the variability in beta-thalassemia phenotype. At position -160bp upstream of exon 1 of the AHSP gene, two main homopolymers (T18 and T15) have been reported that may influence the AHSP expression and hence the hematological phenotype. In particular the frequence of the shorter T15 homopolymer, which is associated with a lower AHSP expression, was much higher than expected (on the basis of the allele frequency in the healthy population) in a group of 9 patients with thalassemia intermedia, due the compound heterozygosity for beta-thalassemia and the triple alpha globin gene (Mei et al, 2006). We have studied the frequency of T15 and T18 homolpolymers in a group of 20 normal subjects and in patients with different thalassemia syndromes, i.e. beta zero 39 homozygotes with thalassemia major (14 patients) and intermedia (19), compound heterozygotes for beta-thalassemia and triple alpha globin gene (13) and simple carriers for beta thalassemia with thalassemia intermedia phenotype (5). We found the following genotype distribution reported in figure1. There is no difference in the frequency of the genotypes among the groups, except in the severe beta-thalassemia carriers, where the short T15 homopolymer is more common. These findings are consistent with the reduced AHSP expression previously reported in the reticulocytes and in the erythroid cultures of these unusually severe beta thalassemia carriers. (Galanello et al, abs 1881. ASH 2003). Therefore, only in the peculiar group of beta-thalassemia carriers with the clinical features of thalassemia intermedia, the AHSP genotype appears to be a relevant contributory factor in the hematological phenotype.
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Disclosure: No relevant conflicts of interest to declare.
