[Genotype of thalassemia genes and the polymorphism of β- globin gene in Cantonese].

Objective: To understand the genotype of α and β-globin, as well as the polymorphism of β-globin gene in Cantonese in recent years, and to provide an effective genetic diagnosis for thalassemia (thal).

Methods: The single-tube complex PCR was used to detect 3 types of deletional α-thal, reverse dot blotting (RDB)/PCR to detect 3 kinds of undeletional α-thal-αCS, αQS, αWSand 18 kinds of β-thal mutations which were common in Chinese population. A total of 454 cases from Guangdong were undergone thal genotype genetic diagnosis. Among the 454 cases, 142 cases were selected to perform the single nucleotide polymorphisms (SNPs) analysis of β- globin gene by denaturing high-performance liquid chromatography (DHPLC)combining the whole gene sequencing.

Results: Of the 454 cases, 438 were diagnosed as thalassemia, including 246 of α-thal, 164 of β-thal and 28 of αβ-thal. In 246 α-thal cases, deletions were the dominant mutations, including 197 cases of αα/--(SEA), 20 of αα/-α(3.7) and 9 of αα/-α(4.2). In 164 β- thal cases, heterozygotes accounted for 92.7% (152/164), the main genotypes were CD41- 42, IVS-II-654, ﹣28 and CD17, and the dual heterozygotes and homozygotes accounted for 4.9% (8/164) and 2.4% (4/164), respectively. The result of β-globin gene screening by DHPLC combining with sequencing was consistent with that of RDB. Moreover, we also found 9 kinds of SNP, in which 2 were unreported, the IVS-I-13 G> A and IVS-II- 310 T>C. In the tested samples, the frequency of 4 kinds SNP was high, among which 3 kinds SNPs-rs713040, rs10768683 and rs1609812 were carried together.

Conclusion: The dominant genotypes were αα/--(SEA) in α-thal cases, CD41-42, IVS-II-654, -28 and CD17 in β-thal. The frequency of β-thal heterozygotes, homozygotes and αβ-thal is high. DHPLC combining the whole β-globin gene sequencing can effectively detect the common β-thal mutation and even new mutations or SNPs. In Cantonese, the frequency of SNP rs713040, rs10768683, rs7480526 and rs1609812 of β-globin gene was high, and there may exist genetic linkage between rs713040, rs10768683 and rs1609812.