A novel polyadenylation signal mutation in the α2‐globin gene causing α thalassaemia

Summary. In a family of Indian origin we have identified a deletion of two bases at the polyadenylation signal sequence of the α2-globin gene (AATAAA AATA). Three individuals heterozygous for this mutation display an αo-thalassaemialike phenotype. Single-stranded conformation analysis and automatic sequencing showed no additional mutations in either α1- or α2-globin genes. A previously described polyadenylation sequence mutation (AATAAA AATAAG), αTSaudiα, causes HbH disease in homozygotes. In this study the patients heterozygous for the AATA(-AA) mutation show a similar phenotype observed in the αTSaudiα heterozygotes. This confirms the observation that the inefficient transcriptional termination due to mutations of the polyadenylation sequence of the α2-gene might interfere with the α1-gene expression.