常染色体隐性遗传先天性角化不良一例及TERT基因突变研究

【摘要】 目的 报告1例常染色体隐性遗传先天性角化不良，检测其致病基因突变情况。方法 采集先证者及其父母外周血，提取基因组DNA，以100例健康人作为对照，运用Illumina Nextseq500测序仪检测先证者家系皮肤病相关基因编码区域的序列突变情况，致病性突变经PCR?Sanger测序验证。运用生物信息学软件Clustalw2.0、PyMOL、PolyPhen?2、SIFT及FATHMM分别对基因突变位点的保守性、蛋白结构变化及致病性进行预测。结果 先证者临床表现为颈胸部网状皮肤异色、腋窝点状色素沉着，部分趾甲萎缩、表面粗糙及口腔黏膜白斑，血常规及肝功能指标部分异常。基因检测显示，先证者携带TERT基因c.2452G>A（p.Val818Met）与c.2594G>A（p.Arg865His）复合杂合突变，其中c.2452G>A突变在HGMD中未见收录。母亲携带c.2452G>A杂合突变，父亲及100例健康对照TERT基因未见突变。生物信息软件分析显示，多个物种TERT蛋白在818与865位氨基酸位点分别为高度保守与完全保守，基因突变后对应蛋白结构存在差异。依先证者临床表现、基因检测、辅助检查及生物信息分析结果，最终诊断为常染色体隐性遗传先天性角化不良。结论 TERT基因c.2594G>A（p.Arg865His）与c.2452G>A（p.Val818Met）复合杂合突变可能是导致该先证者临床表型的原因。

Autosomal recessive dyskeratosis congenita: a case report and TERT gene mutation analysis

【Abstract】 Objective To report a case of autosomal recessive dyskeratosis congenita, and to detect mutations in its causative genes. Methods Peripheral blood samples were collected from the proband and her parents, genomic DNA was extracted, and 100 unrelated healthy individuals served as controls. The Illumina Nextseq500 sequencer was used to detect sequence variations in coding regions of exons of the skin disease-related genes in the proband′s family, and the causative mutation was verified by PCR-Sanger sequencing. The conservation and pathogenicity of gene mutation sites and corresponding protein structure changes were predicted by using bioinformatics softwares Clustalw2.0, PyMOL, PolyPhen-2, SIFT and FATHMM. Results The proband clinically presented with reticular poikilodermatous patches on the neck and chest, punctate pigmentation on the axilla, atrophy of some toenails, rough skin and oral leukoplakia, accompanied by abnormality in some indicators of routine blood tests and liver function. Genetic testing showed that the proband carried compound heterozygous mutations c.2452G>A （p.Val818Met） and c.2594G>A （p.Arg865His） in the TERT gene, and the c.2452G>A mutation was not included in the Human Gene Mutation Database. The proband′s mother carried a heterozygous mutation c.2452G>A, and no mutation was identified in the TERT gene of her father or 100 healthy controls. Bioinformatics analysis showed that the amino acid positions 818 and 865 of TERT proteins in multiple species were highly conserved and completely conserved respectively, and the corresponding protein structures changed after the above gene mutations. Based on the clinical manifestations, genetic testing, auxiliary examinations, and bioinformatics analysis results, the patient was finally diagnosed with autosomal recessive dyskeratosis congenita. Conclusion The compound heterozygous mutations c.2594G>A （p.Arg865His） and c.2452G>A （p.Val818Met） in the TERT gene may be responsible for the clinical phenotype of the proband.