Molecular Characterization of β-Thalassemia in Taiwan and the Identification of two new Mutations

Abstract

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 S35-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.

Rapid detection of ?-globin gene (HBB) mutations coupling heteroduplex and primer-extension analysis by DHPLC

“…Apart from some long-segment deletions, most mutations resulting in b-thalassemia involve a single or several nucleotides of the b-globin gene (HBB; MIM# 141900) [Henthorn et al, 1990;Kazazian, 1990]. At this time, approximately 200 different mutations have been reported worldwide for this malady, and each representative ethnic group reflecting a specific focus for this disease features its own particular common mutations [Abdullah et al, 1996;Baysal and Carver, 1995;Ko et al, 1997;Ko and Xu, 1998;Thein et al, 1990].…”

“…Due to the high prevalence rates of b-thalassemia in Taiwan, national screening programs have been shown to be effective in reducing the incidence in the general population. Polymerase chain reaction (PCR)-based techniques for diagnosis of b-thalassemia have been commonly used to study the molecular defects of b-thalassemia sufferers in Taiwan for a number of years [Ko et al, 1997;Ko and Xu, 1998]. The most sensitive screening technique for genes that predisposes patients to certain genetically based diseases is direct sequencing, although such sequencing is technically demanding, costly, and time-consuming.…”

Parallel minisequencing followed by multiplex matrix-assisted laser desorption/ionization mass spectrometry assay for β-thalassemia mutations

“…According to previous reports (Ko et al 1997), we were able to detect most frequently occurring mutations, apart from the deletion type, up to a level of 98% for the HBB mutations among the general Taiwanese population.…”

“…Specific human populations at risk for b-thalassemia each carry a different subset of HBB alleles represented by a small number of common high-frequency mutations and several low-frequency mutations. Among the Chinese population in Mainland China, Taiwan, and North America, 27 alleles of HBB have been identified (Baysal and Carver 1995;Chiou et al 1993;Kazazian 1990;Ko et al 1997;Liang et al 1994;Lin et al 1991Lin et al , 1992Xu et al 1996). However, in the more restricted Taiwanese population, only eight point mutations account for a great majority (98%) of bthalassemia cases.…”

“…Although large deletions are sometimes observed, most b-thalassemiacausing mutations involve one or several nucleotides of the b-globin gene (HBB; MIM # 141900) (Henthorn et al 1990;Kazazian 1990). Currently, approximately 200 different mutations have been reported worldwide to be associated with this disease, and various ethnic groups affected by b-thalassemia each display their own particular common mutation(s) (Abdullah et al 1996;Baysal and Carver 1995;Ko et al 1997) as well as a variable number of rare alleles (Weatherall and Clegg 2001). For example, in the Southeast Asian (Weatherall and Clegg 2001) and Chinese populations, five b-globin gene alleles (CD41/42 -TCTT, IVS-2 +654 C>T, 28 A>G, CD17 A>T, and CD71/72 +A) account for more than 90% of all b-thalassemia-causing mutations (Ko and Xu 1998).…”