Molecular analysis of β-thalassemia in South Vietnam

Abstract

In Vietnam, the carrier rate for β-thalassemia varies from 1.5% to 25% depending on the ethnic groups of the population. The molecular basis of β-thalassemia in South Vietnam was studied in 50 unrelated β-thalassemia patients. Of these, 31 had β-thalassemia/Hb E, 18 were homozygous for β-thalassemia, and 1 carried the β-thalassemia trait. The majority of the patients were Kinh, four were Chinese, and two were Kinh-Chinese. All had severe anemia and received blood transfusions regularly, every 1-3 months. Hepatosplenomegaly was found in all patients, and splenectomy had been done in six patients. Normal α-globin genotype (αα/αα) was found in all subjects. Reverse dot-blot hybridization using oligonucleotide probes specific for Southeast Asian mutations can detect β-thalassemia in 60 chromosomes in addition to 31 chromosomes with βEmutation. Excluding the βEgene, six previously reported Thai and Chinese β-thalassemia mutations were found, including codons 41/42 (-TCTT) 35.3%, codon 17 (A→T) 25.0%, -28 (A→G) 7.3%, codons 71/72 (+A) 7.3%, IVS-II nt 654 (C→T) 7.3%, and IVS-I nt 1 (G→T) 6.0%. The Vietnamese frameshift mutation at codon 95 (+A) was detected by ARMS in seven chromosomes (10.3%). DNA polymorphism of the β-globin gene cluster carrying the codon 95 mutation was - + - - - - - + forGγ/XmnI, ε/HincII,Gγ/HindIII,Aγ/HindIII, Ψβ/HincII, 3′ Ψβ/HincII, β/AvaII, and 3′β/BamHI, respectively. The remaining mutation detected by the gap PCR was a large deletion known as the ChineseGγ(Aγδβ)O-thalassemia. The two most common mutations were the frameshift at codons 41/42 (-TCTT) and the nonsense mutation in codon 17 (A→T). Thus β-thalassemia mutations in South Vietnam is similar to the previous report from the North, although at different frequencies. This result will help to establish a center for prenatal diagnosis and for prevention and control of thalassemia in Vietnam. © 2002 Wiley-Liss, Inc.