Characterization of beta-thalassemia mutations among the Japanese.

Characterization of beta-thalassemia mutations were attempted for 29 Japanese families clinically diagnosed as having beta-thalassemia. Following the identification of a mutation by cloning and sequencing, all families were screened for this particular mutation, using biotinylated allele-specific oligonucleotide probes. Seven different mutations were detected in 17 families: Six families had the frameshift mutation at codons 41/42, resulting from a 4 nucleotide deletion (TTCTTT----TT); four had the deletion at codons 127/128 (CAGGCT----CCT); and three had the TATA box mutation at nucleotide -31 (A----G). Four additional families had mutations at codon 24 (GGT----GGA), codon 26 (GAG----AAG), IVS-II-654 (C----T) and codon 110 (GTG----CCG), respectively. The newly discovered deletion mutation at codons 127/128, and mutations at nucleotide -31, and at codon 110 are peculiar to Japanese, and have not been found in any other ethnic group. The haplotypes of the beta-globin gene cluster were also determined. Some of the haplotypes and beta-thalassemia mutations are identical to those reported in the Chinese population. However, it is noteworthy that nearly half of the beta-thalassemia mutations were unique to Japanese.