Genetic defects in the thalassemias.

In summary, the beta-thalassemias are models for the study of human genetic disease. Defining the genetic defects in and surrounding the beta-globin gene in the beta(+)- and the beta(0)-thalassemias has resulted in new insights into the relationships between changes in gene structure and abnormalities in gene function. The region 5' to the beta-gene, the coding regions within the gene, and the IVS have all been found to contain single nucleotide defects which diminish or abolish beta-globin mRNA production and the production of beta-globin. The ability to isolate beta-globin genes by cloning, and to express these beta-globin genes in cells, has given remarkable insights into the relationship between globin gene structure and globin gene function. In addition, new technology is available for the antenatal diagnosis of the beta-thalassemias based on the knowledge of the specific defects in these genes, with the use of oligomers to detect single nucleotide changes. Finally, recent advances have suggested new approaches to gene therapy in these disorders using gene transfer.