常染色体显性遗传肾小管间质病中UMOD,REN,HNF1B基因筛查及功能研究

Study of autosomal dominant tubulointerstitial kidney disease in a Chinese cohort

目的在我们收集的中国人常染色体显性遗传小管间质性肾病(autosomal dominant tubulointerstitial kidney disease,ADTKD)的队列中,进行该病致病基因UMOD/REN/HNF1B的突变筛查,同时对新发现的UMOD基因突变进行功能研究,建立ADTKD的遗传诊断基本流程。方法根据KDIGO指南纳入了44例ADTKD疑诊患者及家系,收集临床资料。首先使用一代测序的方法检测UMOD,REN,HNF1B的致病点突变;然后应用多重连接探针扩增技术(multiple ligation-dependent probe amplification,MLPA)进行HNF1B拷贝数变异检测。利用UMOD野生型质定点突变的方法构建突变质粒,转染HEK293细胞,Western Blot方法检测成熟型尿调蛋白表达量的变化。结果 44例先证者中共检出11例突变,10例位于UMOD基因,1例位于HNF1B基因。UMOD基因突变中,3例为国际上尚未报导的新突变(p.Cys35Tyr,p.Asn38Ile p.Cys287Phe)。在该人群中,REN基因点突变和HNF1B基因的拷贝数变异均未检出。将44例先证者分为UMOD突变和未突变组,对比两组临床资料,但两组没有显著性差异。突变质粒转染HEK293细胞表达的成熟型尿调蛋白明显减少(F=14.241,P<0.001)。结论本研究中有25%的患者检测出基因突变,以UMOD基因为主,且均为点突变,点突变是ADTKD的主要致病原因。一代测序是检测该疾病直接有效的方法。临床表现不能作为疾病诊断的标准,应进行一系列的致病基因的监测,并通过初步的功能检测对突变的致病性进行验证。

Objectives In the study, we screened genetic variations in UMOD, REN and HNF1B genes in a Chinese autosomal dominant tubulointerstitial kidney disease （ADTKD） cohort and studied the pathogenesis of ADTKD with novel UMOD mutations. Methods Forty-four probands from 44 different families were re- cruited according to the KDIGO report of diagnostic criteria for suspected ADTKD. We sequenced all exons of the three genes and used multiple ligation-dependent probe amplification （MLPA） assays for copy number variations in HNFIB. We then detected uromodulin expression after transfection of the mutant UMOD cDNA plasmid into HEK293 （human embryonic kidney） cells. Results We detected 11 mutations （10 in UMOD, 1 in HNFIB） in this cohort, and 3 of them （c.104G〉A, c.ll3A〉T and c.860G〉T） were novel mutations in UMOD. Point mutations in REN and copy number variations in HNFIB were not found. We divided the 44 probands into two groups according to the presence and absence of UMOD mutation and found no distinct dis- crimination in clinical characteristics between the two groups. Uromodulin ex pression were significantly de- creased in HKE293 cells after transfected with the mutant plasmid （F=14.241, P〈0.001）, consistent with the previous research results. Conclusions About 25% of patients in our ADTKD cohort were found to have mu- tations in UMOD gene. Clinical features were nonspecific in patients with UMOD mutations. These results in- dicate that gene sequencing is one of the important methods for the diagnosis of ADTKD.