Ⅰ型原发性草酸尿症家系AGT基因新突变鉴定

A novel mutation of human liver alanine:glyoxylate aminotransferase causes primary hyperoxaluria type Ⅰ in PH1 family

目的分析Ⅰ型原发性草酸尿症(PH)家系的遗传方式、临床特征及致病基因丙氨酸乙醛酸氨基转移酶(AGT)突变。方法以2012年11月上海交通大学医学院收治的1例PH患者为研究对象,通过家系调查和血尿草酸浓度离子色谱分析,直接测序法分析AGT基因。同时选取100名健康正常人作为对照。结果该家系共有2例患者确诊为Ⅰ型原发性草酸尿症(PH1),遗传特点符合复杂常染色体隐性遗传。AGT基因测序分析发现先证者与其父亲8号外显子均存在一个新的杂合插入突变(C.946_947insAG),在蛋白水平上该突变引起AGT第275位丝氨酸开始的移码突变,导致羧基末端的119个氨基酸替换缩短为异常的38个氨基酸(P.Ser275Arg fs*38),且先证者与其母亲第2号外显子第467位碱基均存在杂合点突变(C.467G>A),导致(P.Gly116Arg),此突变为已报道过的致病点突变。结论一个新的AGT突变位点被确定与隐性遗传性PH1有关。这是国内首次对遗传性PH1进行基因学研究。

Objective To investigate the genetic causes of a family with primary hyperoxaluria type I （PH1） by sequen- cing glyoxylate aminotransferase （AGT） gene coding liver alanine. Methods We recruited a family with severe phenotype of PH1. Main symptoms and laboratory data were analyzed. Genomic DNA was extracted from peripheral blood and 11 pairs of oligonucleotide primers were designed for amplifying all 11 exons of AGT gene. Polymerase chain reaction products were sequenced and mutation identifications were performed by Sequencing Analysis software. Results Two patients were diag- nosed with PH1 in this family, and the genetic characteristics were in accordance with autosomal recessive inheritance. A no- vel 2-bp duplication at nucleotide 946947 （ C. 946 947insAG） in exon 8 of AGT was identified by direct sequencing anal- ysis. This duplication altered the encoded protein through codon 275, and resulted in a reading frame shift for extra 38 con- dons （P. Ser275Arg fs ＊ 38） instead of 119 before the new stop condon at position 312. Besides, heterozygous mutations （C. 467G 〉 A） existed at the position 467 of exon 2 in the proband and his mother, resulting in P. Gly116Arg, which is a pathogenic mutation reported previously. Conclusion Complex autosomal recessive inherited PH1 presents with severe clinical phenotypes. A novel AGT mutation is identified with PH1.