一个掌跖角化牙周破坏综合征家系CTSC基因的突变鉴定

Screening of CTSC gene mutations in a Chinese pedigree affected with Papillon-Lefevre syndrome

目的对一个掌跖角化牙周破坏综合征家系进行临床表型分析和CTSC基因突变检测，揭示其分子机制，为遗传咨询提供依据。方法通过临床表型、口腔检查等进行临床诊断。用PCR扩增CTSC基因的外显子，之后采用Sanger测序法进行突变筛查，随后用PolyPhen-2和SIFT软件进行突变有害性预测，同时用Swiss—Port软件预测CTSC蛋白的三级结构，并采用荧光定量PCR对患者及其父母的CTSC基因的mRNA进行定量分析，用Western印迹杂交检测野生型和突变型CTsc蛋白的表达差异。结果患者CTSC基因第7外显子存在c．901G〉A（p．G301S）纯合错义突变，其父母均为突变携带者。该突变位于酶的高度保守区，有害性预测结果显示为有害，导致蛋白三级结构发生改变，可能影响组织蛋白酶C的活性。CTSC基因突变型mRNA和蛋白的表达量与野生型的差异无统计学意义。结论首次在中国人群中发现CTSC基因c．901G〉A突变可导致掌跖角化牙周破坏综合征，扩展了CTSC基因的突变谱。

Objective To analyze the clinical phenotype of a Chinese pedigree affected with Papillon- Lefevre syndrome （PLS） and detect mutation of CTSC gene. Methods Clinical phenotypes were noted, and oral examination for the proband was carried out for the clinical diagnosis of PLS. PCR and Sanger sequencing were used to identify potential mutation of the CTSC gene, Functional effect of the mutation was predicted with SIFT and PolyPhen-2. Swiss-Port was used to predict the tertiary structure of wild type and mutant proteins. The mRNA and protein expression were analyzed by real-time PCR and Western blotting. Results A homozygous mutation c. 901G〉A （p. G301S） in exon 7 of CTSC gene was identified in the patient. Both parents of the patient had carried a heterozygous c. 901G〉A mutation. The mutation was located in the conserved region of CTSC enzyme and was predicted to be damaging by changing the structure of the protein, which could affect the activity of Cathepsin C. However, no significant difference was found in the expression of p. G301S variant at the mRNA and protein levels compared with that of the wild type CTSC gene. Conclusion The c. 901G〉A mutation of the CTSC gene was first reported in China, which has expanded its mutation spectrum.