Natural deletions involving alpha-major regulatory element constitute a particular category of alpha-thalassemia determinants in which the alpha-globin genes are physically intact but functionally inactive.
Restriction endonuclease mapping of nondeletion alpha-thalassemia determinants from a variety of racial groups showed no detectable abnormalities within a 40-kilobase region of the zeta-alpha globin gene cluster.
We have identified an individual with alpha-thalassemia in whom structurally normal alpha-globin genes have been inactivated in cis by a discrete de novo 35-kilobase deletion located approximately 30 kilobases 5' from the alpha-globin gene cluster.
The coinheritance of a nondeletional form of alpha thalassemia (alpha alpha T) was suspected because of the severity of the proband's phenotype and the presence of normal alpha-globin gene fragments in the father.
alpha-Thalassemia (alpha-thal) is a widespread genetic disorder throughout the world caused primarily by reduced synthesis of the alpha-globin chains, and it has been found at a high incidence in Turkey.
Accurate genotyping of alpha globin determinant is absolutely required as there is a possibility that an interaction of this unusual double mutation with other common alpha0 thalassaemias (--/-alphaT) can give rise to a very severe, probably fatal, alpha thalassaemia.
In alpha-thalassemia-1 and the nondeletion type of hemoglobin-H disease the two alpha-globin genes are at two loci on one chromosome and none reside on the other chromosome.
For identifying the α-thalassemia (α-thal) genotype, investigation of common Mediterranean α-globin gene deletions (-α3.7, -α4.2 -α20.5 and --MED) was performed by Gap-PCR.
Accurate genotyping of alpha globin determinant is absolutely required as there is a possibility that an interaction of this unusual double mutation with other common alpha0 thalassaemias (--/-alphaT) can give rise to a very severe, probably fatal, alpha thalassaemia.
Previous studies have suggested that HbF levels in SS individuals with alpha-thalassemia (two or three functional alpha-globin genes) are lower than HbF levels in SS individuals with four normal alpha-globin genes.
Despite discoveries concerning the molecular abnormalities that led to the thalassemic syndromes, it still is not known how accumulation of excess unmatched alpha-globin in beta thalassemia and beta-globin in alpha thalassemia leads to red blood cell hemolysis in the peripheral blood, and in the beta thalassemias particularly, premature destruction of erythroid precursors in marrow (ineffective erythropoiesis).
alpha-Thalassemia is common in southeast Asia and the Mediterranean, where the predominant lesion seems to be a deletion of one or more of the four gene loci responsible for alpha-globin chain production.
Furthermore, alpha-globin gene analysis of 100 random cord bloods showed that five out of 100 had the common type of alpha-thalassaemia caused by a single alpha-globin gene deletion (-alpha).
The most common causes of alpha-thalassemia are deletions that remove one or both functional alpha-globin genes, with a small proportion of cases involving nondeletional mutations of the alpha2- or alpha1-globin genes.
From the nature of substituted residues in α2-globin, it is widely expected that this mutation leads to unstable and truncated protein and should be detected in couples at risk for α-thalassemia.
To identify which of these factors may contribute to the modification of childhood homozygous, high-hemoglobin A2 (HbA2) beta-thalassemia in Greece, the interaction of alpha-thalassemia, types of beta-thalassemia mutations, and the presence of a polymorphic site 5' to the G gamma-globin gene, which has been described as associated with increased gamma-globin chain production in some cases, was assessed.
The frequency of deletional alpha-thalassaemia in a Javanese population sample (n = 103) was investigated at three restriction sites of the alpha-globin gene (BamHI, BglII and RsaI).