Initiation codon mutation as a cause of alpha thalassemia

Area of Science:

• Genetics
• Molecular Biology
• Hematology

Background:

• Alpha-thalassemia is a genetic blood disorder characterized by reduced or absent synthesis of alpha-globin chains.
• Nondeletion alpha-thalassemia results from mutations affecting alpha-globin gene expression or stability, rather than gene deletion.
• Hemoglobin H disease is a severe form of alpha-thalassemia.

Purpose of the Study:

• To identify the genetic basis of nondeletion alpha-thalassemia in Sardinian patients.
• To characterize a novel mutation in the alpha-globin gene responsible for thalassemia.
• To develop a diagnostic method for the identified mutation.

Main Methods:

• Cloning and sequence analysis of alpha-globin genes.
• Analysis of globin mRNA levels.
• Restriction fragment length polymorphism (RFLP) analysis using NcoI enzyme.

Main Results:

• A new mutation changing the initiation codon (ATG to ACG) in the alpha 2-globin gene was identified.
• This mutation abolishes the function of the alpha 2-globin gene and decreases its mRNA output.
• The mutation was detectable by NcoI restriction analysis in genomic DNA.
• Six out of seven Sardinian patients with nondeletion alpha thalassemia carried this specific mutation.

Conclusions:

• A novel initiation codon mutation in the alpha 2-globin gene is a frequent cause of nondeletion alpha-thalassemia in Sardinia.
• This mutation significantly impairs alpha-globin synthesis, contributing to thalassemia.
• Restriction analysis with NcoI provides an effective diagnostic tool for this specific thalassemia lesion.