Molecular biology of hemoglobin: its application to sickle cell anemia and thalassemia.

During the past 15 years there have been remarkable advances in our understanding of the molecular biology of hemoglobin synthesis and the abnormalities in hemoglobinopathies and thalassemia. The globin genes were among the first mammalian structural genes that were cloned and the DNA sequence of the human globin gene clusters has since been completely delineated. During the last ten years, we have also learned of the many deletions and point mutations that give rise to hemoglobin-opathies and thalassemia. In addition, the sequences that control erythroid specific expression of the globin gene has also been revealed. These findings have contributed to our understanding of the pathophysiology of the diseases and have allowed the institution of accurate DNA diagnostic methods to be applied to prenatal diagnosis. As increased fetal hemoglobin synthesis is known to ameliorate the severity of the disease in disorders such as sickle cell anemia and thalassemia, agents which increase the level of fetal hemoglobin synthesis are being tested. Also, the discovery of DNA sequences and transacting factors which are responsible for high erythroid globin gene expression [4] may provide more effective means of gene therapy.