The studies of hemoglobinopathies and thalassemia in China—the experiences in Shanghai Institute of Medical Genetics

• Published in: Clinica chimica acta 2001-11, Vol.313 (1), p.107-111
• Main Authors: Zeng, Yi-tao, Huang, Shu-zhen
• Format: Article
• Language: English
• Subjects: Anemias. Hemoglobinopathies; beta-Thalassemia - drug therapy; beta-Thalassemia - epidemiology; beta-Thalassemia - genetics; Biological and medical sciences; China - epidemiology; Diagnosis; Disease; Diseases of red blood cells; Globins - genetics; Hematologic and hematopoietic diseases; Hemoglobin; Hemoglobinopathies - epidemiology; Hemoglobinopathies - genetics; Heterozygote; Homozygote; Humans; Hydroxyurea - therapeutic use; Incidence; Medical sciences; Reverse Transcriptase Polymerase Chain Reaction; RNA Splicing; RNA, Messenger - genetics; Screening; Treatment
• ISSN: 0009-8981; 1873-3492
• DOI: 10.1016/S0009-8981(01)00660-X

Background: In the past two decades, a large-scale survey of hemoglobinopathies and thalassemia was carried out in mainland China, involving nearly one million people in 28 provinces. The incidences of hemoglobin (Hb) variants, α-thalassemia and β-thalassemia were 0.33%, 2.64% and 0.66%, respectively. The chemical structural analysis identified 67 Hb variants. Among them, 20 are new variants. The analysis of the α-globin gene organization in 111 HbH patients showed 76 cases (68.5%) were of the deletion type, 8 had Hb Constant Spring and the other cases were of non-deletion type. The results of the molecular characterization of more than 200 β-thalassemia alleles showed that the most common types of β-thalassemia mutations in China are CD 41/42 (−4 bp), IVS-II-nt.654 C→T, CD 17 A→T, CD 71/72 (+A) and −28 A→G. Methods: To explore the simple method for molecular diagnosis of β-thalassemia, multiplex allele-specific amplification (MAS-PCR) was used that could simultaneously detect the above five common types of β-thalassemia mutations. Results: Based on the molecular analysis of β-thalassemia intermedia, β-thalassemia homozygotes or compound heterozygotes combined with α-thalassemia, as well as the conjunctive abnormalities of β-thalassemia heterozygote with triplicated haplotype of α-globin genes, were the most common cause of thalassemia intermedia in China. We also used the RT-PCR quantitation method to show that the most common β-thalassemia allele, IVS-II-nt.654 C→T, still produced a small amount (about 15%) of normally spliced β-globin mRNA, therefore, causing β +-thalassemia. In clinical trials of hydroxyurea (HU) treatment for β-thalassemia patients, we found that HU may enhance the expression of the β-globin gene in some patients, leading to an alleviation of clinical symptoms. In the studies of the reversal of aberrant splicing of IVS-II-nt.654 C→T allele by the antisense approach, we constructed a mammalian expression vector that can produce an antisense RNA targeting against the aberrant splice sites of IVS-II-nt.654 C→T pre-mRNA. Conclusions: The results indicated that the antisense RNA produced from the vector could efficiently suppress the aberrant splicing pattern and restore the correct splicing pathway in vitro and in vivo, leading to the improvement of globin chain biosynthesis in thalassemia cells.