苯丙氨酸羟化酶基因c.158G>A(p.Arg53His)突变患儿随访及突变位点功能评估  

Follow-up of two newborns with c.158G>A(p.Arg53His)mutation in PAH gene and assessment of the site function

作　　者：王杰 朱博 张丽春 赵一桐 王晓华 贾跃旗 WANG Jie;ZHU Bo;ZHANG Lichun;ZHAO Yitong;WANG Xiaohua;JIA Yueqi(Genetic Eugenic Department of Inner Mongolia Maternity and Child Health Care Hospital,Hohhot 010020,China;State Key Laboratory of Reproductive Regulation&Breeding of Grass Land Livestock,College of Life Science,Inner Mongolia University,Hohhot 010021,China;Medical Genetics and Prenatal Diagnosis of Sichuan Provincial Maternity and Child Health Care Hospital,Chengdu 610041,China)

机构地区：[1]内蒙古自治区妇幼保健院遗传优生科,内蒙古呼和浩特010020 [2]内蒙古大学省部共建草原家畜生殖调控与繁育国家重点实验室,内蒙古呼和浩特010021 [3]四川省妇幼保健院医学遗传与产前诊断科,四川成都610041

出　　处：《浙江大学学报（医学版）》2021年第4期444-453,共10页Journal of Zhejiang University(Medical Sciences)

基　　金：国家自然科学基金(81860168)。

摘　　要：目的:评价苯丙氨酸羟化酶(PAH)基因c.158G>A(p.Arg53His)突变的临床意义。方法:持续监测2例携带PAH基因p.Arg53His突变的疑似高苯丙氨酸血症患儿血液中苯丙氨酸(Phe)浓度,分析患儿的临床生化特征,应用T-Coffee系统分析PAH蛋白的跨种属保守性,应用Swiss-Model对正常结构及变异结构的PAH进行蛋白质三维结构建模及比对分析突变所致蛋白质空间结构的改变。检索现有数据库及文献统计p.Arg53His突变的人群携带率,应用等位基因表型值(APV)与基因型表型值(GPV)预测系统对该突变相关表型进行预测。结果:2例新生儿在PAH基因上分别检出两个突变:c.611A>G(p.Tyr204Cys)、c.158G>A(p.Arg53His)和c.1238G>C(p.Arg413Pro)、c.158G>A(p.Arg53His)。2例新生儿能耐受正常饮食,在随访期间血Phe水平在正常范围内。例2的母亲为p.Arg53His纯合突变,长期未进行低蛋白质、低Phe饮食干预,血Phe浓度、Phe/酪氨酸比值均在正常范围。突变的氨基酸在13个不同物种间并非高度保守。三维结构建模结果显示,p.Arg53His突变使得PAH第53位和第49位氨基酸之间的氢键由2个减少为1个,降低了二聚体的稳定性。p.Arg53His在高苯丙氨酸血症患者中的等位基因频率为0.01508,在健康人群中的等位基因频率为0.001621,其中东亚人群中的携带率最高,为0.01373。APV与GPV系统预测结果显示,该突变与轻度高苯丙氨酸血症型别相关。结论:PAH基因p.Arg53His突变与不同突变组合为复合杂合状态可引起临床表型差异。p.Arg53His突变引起体内酶活性的降低不足以出现苯丙酮尿症临床症状,分类为“可能良性”。Objective:To investigate the clinical significance of PAH c.158G>A(p.Arg53His)mutation.Methods:The blood phenylalanine(Phe)was continuously monitored in 2 unrelated newborns with suspected hyperphenylalaninimia(HPA)carrying PAH c.158G>A mutation.The cross-species conservation of the mutant amino acid was analyzed using T-Coffee.Swiss-Model software was used to construct a 3D protein structure and the impact of candidate mutations on the secondary structure of the protein product was analyzed.The population carrying rate of the p.Arg53His mutation was analyzed by literature searching.Allelic phenotype values(APV)and genotypic phenotype values(GPV)were used to predict the phenotype associated with the mutation.Results:Two mutations of PAH gene were detected in each newborn:c.611A>G(p.Tyr204Cys),c.158G>A(p.Arg53His)and c.1238G>C(p.Arg413Pro),c.158G>A(p.Arg53His).Two children tolerated normal diet and plasma Phe levels were within the normal range during follow-up.The mother of case 2 was homozygous with p.Arg53His mutation under the condition of long-term normal diet,and the blood Phe concentration and Phe/Tyr were all within the normal range.The mutant amino acids were not highly conserved among the 13 different species.The 3D structural model showed that p.Arg53His mutation reduced the hydrogen bond from 2 to 1 between the 53rd and 49th amino acids of PAH.The allele frequency of p.Arg53His was 0.01508 in HPA patients and 0.001621 in normal population,while the prevalence of p.Arg53His allele was highest in the East Asian normal population(0.01373).The APV and GPV system predicted that the mutation was related to mild HPA(MHP)type.Conclusion:The different compound heterozygous mutations of p.Arg53His lead to clinical phenotype varieties.The reduction of enzyme activity caused by the mutation of p.Arg53His is not sufficient to cause symptoms of phenylketonuria,so the mutation may be“likely benign”.

关 键 词：高苯丙氨酸血症 苯丙氨酸羟化酶缺乏症 p.Arg53His突变 表型 苯丙氨酸 随访研究 

分 类 号：R722.1[医药卫生—儿科] R596[医药卫生—临床医学]