珠蛋白基因Aγ-196C→T突变导致nd-HPFH的研究

STUDY ON Aγ-196C→T MUTATION INDUCING NONDELETIONAL HEREDITARY PERSISTENCE OF FETAL HEMOGLOBIN

目的：探讨珠蛋白基因Aγ-196C→T突变导致的非缺失型遗传性持续性胎儿血红蛋白综合征（nd-HPFH）的基因突变特点及其合并α地中海贫血的基因突变特点及临床特征。方法：选择2014年7月至2015年8月在广西医科大学第一附属医院进行地中海贫血筛查和基因诊断的患者中胎儿血红蛋白（Hb F）≥4%的130例患者为研究对象,选取30例正常人的DNA测序作为对照。对研究对象进行血常规检测和血红蛋白分析。其γ珠蛋白基因突变应用DNA测序方法分析;α、β地中海贫血基因突变应用反向斑点杂交（RDB）和gap-PCR方法检测。结果：130例Hb F增高的病例中,有9例检出杂合子γ珠蛋白基因Aγ-196C→T突变。9例中有5例为单纯杂合子γ珠蛋白基因Aγ-196C→T突变,血常规结果：Hb 104～132.7g/L,红细胞平均容积（MCV）81.1～96.6fL,红细胞平均血红蛋白（MCH）28.5～33.4pg。血红蛋白结果：Hb F 12%～14.8%,Hb A22.0%～2.2%。有2例Aγ-196C→T突变复合珠蛋白基因Gγ-158C→T突变,血常规显示：Hb分别为144g/L、109.8g/L;MCV分别为95fL、95.05fL;MCH分别为33pg、32.15pg。血红蛋白结果：Hb F分别为16.9%、16%;Hb A2均为1.9%。有1例Aγ-196C→T突变同时复合Gγ-158C→T突变和杂合子α地中海贫血（--SEA/αα）,血常规结果：Hb为117g/L,MCV为77.9fL,MCH为27.8pg。血红蛋白结果：Hb F为13%,Hb A 21.9%。有1例Aγ-196C→T突变复合杂合子α地中海贫血（--SEA/αα）,血常规结果 ：Hb为112g/L,MCV为70.5fL,MCH为22pg。血红蛋白结果 ：Hb F为12.9%,Hb A 21.6%。结论：首次发现Aγ-196C→T突变合并东南亚缺失型α地中海贫血,MCV和MCH较单纯杂合子γ珠蛋白基因Aγ-196C→T突变降低。首次发现Aγ-196C→T突变合并珠蛋白基因Gγ-158C→T突变,其Hb F水平较单纯珠蛋白基因Gγ-158C→T突变明显增高。

Objective：To investigate the gene mutation characteristics and clinical features of the Aγ-196C→T mutation associated with non-deletional hereditary persistence of fetal hemoglobin（nd-HPFH）complicated withα-thalassaemia.Methods：From July 2014 to August 2015,130cases（fetal hemoglobin,Hb F）≥4%）admitted to the First Affiliated Hospital of Guangxi Medical University were recruited in this study,and 30 healthy donors were included as control.Blood cells were counted by blood cell analyzer;Aγ-196C→T mutation were analyzed by DNA sequencing.The quantification of Hb A2 and Hb F levels were performed by high performance liquid chromatography（HPLC）. Gene mutation α-thalassemia andβ-thalassemia were analyzed by reverse dot blot hybridization（RDB）and gap-polymerase chain reaction（gapPCR）.Results：Among 130 cases with elevated levels of Hb F,9cases were identified as heterozygote Aγ-196C→T mutation,and 5cases of them are pure heterozygote Aγ-196C→T mutation.The hematological examination showed that the Hb level is from 104.0g/L to 132.7g/L,mean corpuscular volume（MCV）level is from 81.1fL to 96.6fL and mean corpuscular hemoglobin（MCH）is from 28.5pg to 33.4pg.Hemoglobin analysis showed that elevated Hb F around 12.0%to 14.8% and lower Hb A2 around 2.0%to2.2%.Within those 9cases,2cases are accompanied by Gγ-158C→T mutation.The hematological examination showed the Hb level are 144.0g/L and 109.8g/L respectively.MCV level are 95.00 fL and 95.05 fL respectively and MCH are 33.00 pg and 32.15 pg respectively.Hemoglobin analysis showed that elevated Hb F are 16.9% and 16.0%respectively and the value of Hb A2 are both 1.9%.1case is Aγ-196C→T mutation complicated with Gγ-158C→T mutation and--SEA/αα,the hematological examination showed the Hb level is 117.0g/L.MCV level is 77.9fL and MCH level is 27.8pg.Hemoglobin analysis showed elevated Hb F is 13.0%and lower Hb A2 is 1.9%.1case is Aγ-196C→T mutation compounded with--SEA/αα,the hematological examination showed the Hb level is 112g/L.MCV level is 70.5fL and MCH level is22.0pg.Hemoglobin analysis showed elevated Hb F is 12.9% and lower Hb A2 is 1.6%.Conclusion：It is the first time to discover that Aγ-196C→T mutation complicated with the--SEA/αα,in which the MCV and MCH levels are reduced,comparing with the pure heterozygote Aγ-196C→T mutation.It is also the first time to report that Aγ-196C→T mutation is incorporated with Gγ-158C→T mutation,in which Hb F levels is significantly higher than that in the simple mutation of Gγ-158C→T.