中国人先天性肾病综合征NPHS1基因突变

NPHS1 mutations in a Chinese family with congenital nephrotic syndrome

目的分析并确定一个中国先天性肾病综合征(CNS)家系NPHS1基因突变及特征.方法对先证者及其家系成员采用聚合酶链反应(PCR)和DNA直接测序方法进行NPHS1基因突变检测,确定基因突变的位点.同时应用限制性内切酶酶切分析的方法,分析先证者及其家系成员和对照人群的基因组DNA,确定突变特征.结果在本家系的先证者发现同时存在NPHS1的 G928A(D310N)、1893～1900del 8(CGAAACCG)和G2869C(V957L)的3个杂合突变.具有相同表型的姐姐(Ⅲ:11)与先证者的测序结果完全一致,而在表型正常的先证者的同父异母的大姐及对照样本均未发现这些突变.患儿母亲尿检正常,基因检测显示仅有第8外显子G928A突变;患儿父亲尿检也正常,基因检测显示仅存在第14外显子的1893～1900del 8和第21外显子的G2869C突变,没有第8外显子G928A突变.同时还在先证者发现了4 种碱基变异: E117K (rs3814995)、S1105S(rs2071327)、IVS27+45c>t和IVS8+68 a>g,经比对前3种均为单核苷酸多态性,位于内含子内的变异(IVS8+68 a>g)意义有待进一步研究.结论首次发现中国人CNS存在NPHS1基因突变,并证实致病突变为国际首次报道的3个杂合突变.

Objective Congenital nephrotic syndrome （CNS） is defined as heavy proteinuria or nephmtic syndrome occurring before 3 months of age. It is characterized by early onset, resistance to steroid therapy and progressing to end-stage renal disease （ESRD）. In recent years, several genes associated with CNS have been identified, such as NPHS1, NPHS2 and WT1. The mutations of these genes have been identified in the patients with CNS in Finland, other European countries, North Africa, North America, and Asia, respectively. However, the investigation of the above genes has not been performed in Chinese CNS patients. In this study, NPHS1 mutations in a Chinese family with CNS were detected and analyzed. Methods There were two CNS patients in the investigated family. The proband, a 45-day-old boy, was born at fullterm and weighed 2700 g at birth. The placenta weighed 450 g. At the age of 10 days, generalized edema, proteinuria, hypoproteinemia, and hypoalbuminemia were found without renal insufficiency. The proband＇s sister, with the same phenotype and normal renal function, underwent renal biopsy at 5 years of age. Their parents and elder half-sister all had normal phenotypes. Genomic DNA samples were extracted from peripheral bloods of the proband, his family members and 50 unrelated, normal individuals. All 29 exons and exon-intron boundaries of NPHS1 were detected in the proband by polymerase chain reaction （PCR）, direct DNA sequencing, and restriction enzyme analysis. Results Three heterozygous mutations of NPHS1, namely, G928A （ D310N ）, 1893 - 1900del 8 （ CGAAACCG）, and G2869C （V957L）were identified in the proband. These mutations involved exons 8, 14, and 21. The same genotype was found in the proband＇s sister who had the same phenotype, but was not detected in proband＇s elder half-sister who had normal phenotype. Fifty normal individuals had no these mutations. The proband＇s mother with normal urinalysis had G928A （D310N）heterozygous mutation, and the father with normal urinalysis had two heterozygous mutations of 1893 - 1900del 8 （CGAAACCG） and G2869C（V957L）. At the same time, three types of single nucleotide polymorphisms （SNPs）, E117K （rs3814995）, S1105S（rs2071327）, and IVS27 ＋45c 〉 t,were confirmed in the proband. Another variant, IVS8 ＋68 a 〉 g had also been found. Conclusion This is the first report about NPHS1 mutations in Chinese CNS kindred. These three heterozygous mutations of NPHS1 are novel genetic defects of CNS, which have not been described before.