Study of Asians has previously indicated that deletion of alpha-globin structural genes is the predominant lesion in alpha-thalassemias and that Hb H disease occurs when three of four normal alpha loci per cell are deleted.
Expression of (hu)alpha-globin reaches a level of 36% of that of endogenous mouse alpha-globin ((mu)alpha-globin) on a heterozygous mouse alpha-thalassemia background ((mu)alpha-globin knockout, (mu)alpha(+/-)).
These findings support the theory that coinheritance of alpha-thalassemia mitigates the severity of beta-thalassemia and suggest that the protection is most pronounced when two alpha-globin genes are deleted.
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.
The nature of alpha-thalassemia in this patient was investigated both by liquid hybridization and by the Southern method of gene mapping, in which DNA is digested with restriction endonucleases and the DNA fragments that contained the alpha-globin structural gene identified by hybridization with complementary DNA.
Recognizing the pathogenic α-globin gene mutations associated with α-Thalassemia is of significant importance to thalassaemia's diagnosis and management.
Patients with alpha-thalassemia had a lower MCHC than patients with four alpha-globin genes and this was not significantly affected by the level of Hb F. The combination of alpha-thalassemia and high levels of Hb F appears to result in a distinctive S/S phenotype that is similar to the type of S/S disease described in Southern India.
Alpha thalassemia was found in 41 (41.0%) patients compared to 24 (38.1%) controls (P = 0.744), and all were due to the 3.7 κb α-globin gene deletions.
To identify the copy number of α-globin genes in α-thalassemia, we developed a novel method using a multiplex polymerase chain reaction (PCR) in combination with the CE analysis.
The alpha-globin chains are encoded by two duplicated genes (HBA2 and HBA1, 5'-3') showing overall sequence homology >96% and average CG content >60%. alpha-Thalassemia, the most prevalent worldwide autosomal recessive disorder, is a hereditary anemia caused by sequence variations of these genes in about 25% of carriers.
These data showed that factor(s) in the mouse erythroleukemia cell can genetically complement the alpha-globin gene defect in these preleukemia patients with acquired hemoglobin H disease and suggest that altered expression of a gene in trans to the alpha-globin gene may be responsible for the acquisition of hemoglobin H disease in these patients.
Deletion of one or more of them, as occurs in alpha-thalassaemia, leads to a reduced output of alpha-globin mRNA in proportion to the number of alpha-globin genes lost.
Due to the relatively more complex genetics of α-thalassemia, a similar relationship was demonstrated for α-globin gene mutations only from the 1980s, with both single- and double-α-globin gene deletions prevalent in the malarial belt.
In alpha-thalassemia, alpha/beta-globin mRNA ratio correlated with the number of functional alpha-globin genes present, whereas in beta-thalassemia, the ratio provided a good indicator of disease severity.
Hemoglobinopathies caused by highly unstable beta-chain variants have a dominant thalassemia-like phenotype, in which carriers have a clinical expression of thalassemia intermedia, but highly unstable alpha-globin variants are usually only phenotypically apparent when they interact with other alpha-thalassemia mutations.