两例罕见β~0-地中海贫血突变Codon41(-C)的鉴定

Identification of a rare β~0-thalassemia mutation Codon 41(-C) in two unrelated Chinese patients

目的分析2例中国人中罕见的β地中海贫血突变类型。方法对来自云南的两例无亲缘关系、血液学表型与常见地中海贫血基因突变检测结果不符的疑似β地中海贫血样本,采用聚合酶链反应(PCR),Sanger DNA测序和TA克隆测序进行HBB基因突变的鉴定;采用PCR-限制酶切片段长度多态(PCR-RFLP)技术分析β株蛋白基因簇的单倍型和突变源流;建立检测罕见基因突变的单管四引物扩增阻滞PCR(Tetra-primerARMS-PCR)方法,调查云南428例随机傣族样本中罕见基因突变的携带率。结果来自云南地中海贫血流行区的1例汉族和1例傣族患者分别呈现轻度和中度小细胞低色素贫血表型,HbA2和胎儿血红蛋白HbF增高;DNA分析检出罕见β地中海贫血突变Codon41(-C)(HBB:c.126delC),2贫血病例的基因型均为突变杂合子;该突变首次在中国人中报道,其β珠蛋白基因簇单倍型与泰国人中报道的相似;在同一地区的428例傣族样本中未检测到该突变,突变携带率<0.23%。结论 Codon41(-C)是中国人中罕见的地中海贫血突变,可能与泰国傣族人中的突变具有共同源流,可疑患者需要进行基因检测以避免漏诊或误诊,地贫流行区的携带者应进行遗传咨询以减少重症地贫患儿出生。

Objective： To identify rare beta-thalassemia mutation in two Chinese patients. Methods： PCR, Sanger DNA sequencing and TA cloning were used to determine HBB gene mutations in two unrelated patients from Yunnan province of China with β-thalassemia hematological phenotypes but without detecting common thalassemia mutations. β-globin gene cluster haplotypes were investigated by using PCR-RFLP. A single-tube tetra-primer ARMS-PCR method was established and optimized to specifically detect the identified rare thalassemia mutation, and was used to screen the rare mutation in 428 random selected DNA samples from Dai （Thai） population in the southwestern region of Yunnan province, China. Results： One patient with Hart ethnic origin and one patient with Dai （Thai） ethnic background from the thalassemia prevalent region in Yunnan respectively presented mild and moderate microcytic hypochromic anemia, increased HbA2 and fetal hemoglobin （HbF） . DNA analysis revealed a rare β-thalassemia mutation, Codon41 （-C） （HBB： c.126delC） , in heterozygous state in the two patients with anemia, which made the present study the first report of the mutation in China. The beta globin gene cluster haplotypes identified in the patients were very similar to that previously reported in Thai patient from Thailand. The Condon 41 （-C） mutation was not detected in the 428 Chinese Dai （Thai） ethnic individuals, indicating the mutation incidence of the Dai population was less than 0.23%. Conclusion： Codon41 （-C） is a rare thalassemia mutation in Chinese. It may share a common origin with that in Thai ethnic people of Thailand. When encountering patients suspected of the rare mutation, genetic test against the mutation should be carried out to avoid and reduce misdiagnosis. The rare β-thalassemia mutation Carrier from thalassemia prevalent region should consider genetic counseling in order to minimum the birth of children with severe thalassemia phenotype.