Molecular Characterization of Beta-Thalassemia in Taiwan and the Identification of Two New Mutations

Polymerase chain reaction-based techniques were used to study the molecular defects of 480 unrelated beta- thalassemia heterozygotes in Taiwan. Analysis of artificially created restriction sites and gap- polymerase chain reaction were performed to detect four common mutations, i.e. IVS-II-654 (C --> T), codons 41/42 (-TCTT), codon 17 (A --> T), -28 ( A --> G), and a deletional form of delta beta-thalassemia in the Chinese population. In cases with negative or ambiguous results with the aforementioned methods, direct DNA cycle sequencing using either S-35-dATP or a fluorescent dye terminator, was carried out to determine the defects . A total of 14 different mutations have been found in this series. The IVS-II-654 mutation was the most common (39.6%), followed by the codons 41 /42 mutation (37.9%). The four common genotypes accounted for 92 .3% of defects. Two new mutations were detected: codon 31 (- C) and codons 40/41 (+T). Both defects resulted in a frameshift and a premature terminator, the former at codon 60, the latter at codon 43. Although we have studied our cases extensively, the molecular defects in seven alleles are still unknown.