The beta+-thalassemia mutation [IVS-II-5 (G-->C] creates an alternative splicing site in the second intervening sequence.

We report a beta-thalassemia mutation [IVS-II-5 (G-->C)] in a Chinese family. Recently we cloned this beta-globin gene and studied its transient expression in murine erythroleukemia (MEL) cells. Both the thalassemic and normal beta-globin genes were isolated by polymerase chain reaction and TA-vector cloning. When the cloned beta-thalassemic globin gene was introduced into MEL cells, two kinds of spliced cytoplasmic beta-globin RNAs were detected. The predominant RNA was normally spliced, while the less abundant RNA contained an insertion of the first 47 nucleotides of the second intervening sequence localized between exons 2 and 3. These results suggest that the mutation [IVS-II-5 (G-->C)] causes a beta+-thalassemia.