DNA samples from numerous subjects of different racial and ethnic backgrounds, with or without various hemoglobinopathies (classical beta-thalassemia; silent beta-thalassemia, Hb E, sickle cell anemia), were studied for a rearrangement (+ATA; -T) at nucleotide -530 in the 5' flanking region of the beta-globin gene using amplified DNA and 32P-labeled synthetic oligonucleotide probes. The data show that this unusual sequence is a common feature among East-Asians and Blacks (particularly SS patients), and is not associated with mild thalassemic features typical for the silent form of beta-thalassemia, as has been suggested (5).
In an ongoing effort to identify point mutations causing beta-thalassaemia, we have found two previously unreported mutations which are located in the Poly A site of the beta-globin gene. The screening programme used amplified DNA and dot-blot hybridization with several 32P-labelled oligonucleotide probes. DNA samples which remained unidentified by this methodology were subjected to sequencing with 32P-labelled primers and modified T7 DNA polymerase. The newly discovered mutations were confirmed by the dot-blot hybridization technique. One type concerned an AATAAA----AATGAA mutation in the polyadenylation site and was found in one family from Yugoslavia (including one patient with the C----T mutation at codon 29 in trans), one from Bulgaria (the patient had the G----A mutation at IVS-I-110 in trans), and one from Greece (this patient had the C----G mutation at IVS-II-745 in trans). Haematological data for three simple heterozygotes suggested a rather mild beta(+)-thalassemia. The second type involved an AATAAA----AATAGA mutation and was found in one family from Malaysia. The propositus had the beta E mutation on the other chromosome, was originally diagnosed as mild Hb E-beta(+)-thalassaemia, and had Hb A and Hb E percentages which were nearly the same.