导致家族性血尿的COL4A4基因遗传变异分析

Genetic analysis of COL4A4 gene in familial hematuria

目的通过对1个家族性血尿家系进行遗传变异筛查,为家族性血尿病变提供遗传线索和证据。方法本研究纳入的研究对象为1个4代含20名成员的家族性血尿家系。对该家系进行临床资料和实验室检查结果的收集和整理,留取家系中11名成员的外周血并用盐析法提取DNA用于遗传分析。首先选取包括先证者在内的3名家系成员进行全外显子组测序,根据2015年美国医学遗传学与基因组学学会发布的序列变异解读指南进行遗传变异筛选。继而在家系成员中对筛选出的遗传变异位点进行实时荧光定量PCR和Sanger测序验证。结果该家系中6名女性患者有持续性血尿,2人因肾衰竭去世,2人因肾脏以外疾病去世,2人维持肾功能稳定。肾功能稳定2人中1人肾活检病理诊断为IgA肾病,电镜提示弥漫性基底膜病变,不除外Alport综合征。基因检测在家系中发现COL4A4基因(RefSeq NM_000092)的两个点突变,7号外显子c.G446T:p.G149V的变异,以及20号外显子c.G1249A:p.G417R的变异。结论通过对1个家族性血尿家系开展基因检测,发现COL4A4基因的两个新突变(7号外显子c.G446T:p.G149V和20号外显子c.G1249A:p.G417R的变异)与家族性血尿表型相关联。

Objective To define more information for familial hematuria by genetic screening in a pedigree with familial hematuria.Methods This was a 4 generation pedigree included 20 family members.The clinical data and laboratory manifestations of the family members were reviewed and collected from medical records.Meanwhile,the peripheral blood samples of 11 family members of the pedigree were collected,and then DNA samples were extracted by salting out method for genetic analysis.For genetic analysis,firstly,three family members including the proband were selected for whole exome sequencing,and the genetic variations were screened according to the sequence variation interpretation guidelines from the American College of Medical Genetics and Genomics(ACMG)for diagnostic sequence interpretation.Then PCR and Sanger sequencing were used to verify the identified pathogenic variants in all family members in the pedigree.Results In the pedigree,6 female members had persistent hematuria.Among them,2 died due to end-stage renal disease,2 died due to non-renal diseases,and 2 maintained stable renal function.One of the two members with stable renal function was diagnosed as IgA nephropathy by renal biopsy.Moreover,diffuse basement membrane lesions were identified in her renal biopsy sample after the electron microscope examination,which resulted in the suspected diagnosis of Alport syndrome.Genetic testing in this pedigree revealed two novel mutations in COL4A4 gene(NM_000092),c.G446T:p.G149V in exon 7 and c.G1249A:p.G417R in exon 20.Conclusion Two novel mutations of COL4A4 gene(c.G446T:p.G149V in exon 7 and c.G1249A:p.G417R in exon 20)in a hematuria pedigree are related with phenotype of familial hematuria.