中国南方一罕见迟发性脊椎骨骺发育不良大家系的表型和基因型的相关性研究

The Correlation Study of Phenotype and Genotype of a Rare SEDT Family in South China

【目的】揭示一罕见遗传性矮小症家系的分子发病机制,阐明患者表型和基因型的相关性,为今后的产前、植入前基因诊断奠定基础。【方法】在临床初诊、系谱分析的基础上,首先采用高通量测序技术对先证者及其家庭核心成员的DNA样品进行全外显子组测序。通过生信分析找出候选基因,在确定候选基因及其新变异后,采用PCR、Sanger测序、RT-PCR、q-PCR等方法对该新变异的致病性进行系列鉴定。【结果】通过全外测序、Sanger测序验证和生物信息分析,确定TRAPPC2基因及其携带的c.94 delG突变为本病最可能的致病基因突变;通过RT-PCR,排除了IVSas(-1)delG的可能;通过q-PCR检测,证实该突变导致患者和携带者的TRAPPC2基因表达量显著低于正常人群(P<0.01),且蛋白高级结构预测分析显示正常蛋白和突变蛋白的空间结构存在明显差异。根据ACMG的标准,确定为致病性突变。【结论】先证者所患疾病为XR型迟发性脊椎骨骺发育不良(SEDT),TRAPPC2基因的c.94 delG,p.D32T,fsX6是一还未报道的新致病突变,是患者发病的内在原因,其基因型和表型有显著的相关性。该研究进一步丰富了TRAPPC2基因的突变谱,为今后的早期诊防和优生优育打下了良好基础。

【Objective】To reveal the molecular pathogenesis of a family with hereditary dwarfism and the correlation between phenotype and genotype,so as to lay a foundation for prenatal and preimplantation gene diagnosis in the future.【Methods】On the basis of preliminary clinical diagnosis and pedigree analysis,the DNA samples of the proband and his family core members were sequenced by next generation sequencing.The candidate genes were identified by bioinformatics analysis.After the candidate genes and their novel variants were identified,the pathogenicity of the novel variants was identified by PCR,Sanger sequencing,RT-PCR,q-PCR and other methods.【Results】Through whole exon sequencing,Sanger sequencing and bioinformatics analysis,it was confirmed that TRAPPC2 gene and its c.94 del G mutation were the most likely pathogenic mutations in the disease,and the possibility of IVS as(-1)del G was ruled out by RT-PCR.Through q-PCR detection,it was confirmed that the TRAPPC2 gene expression of patients and carriers was significantly lower than that of normal people(P<0.01),and the advanced structure prediction analysis of protein showed that there was a significant difference in the spatial structure of normal protein and mutant protein.According to the criteria of ACMG guidelines,it was identified as pathogenic mutation.【Conclusions】The disease of the proband is delayed spondyloepiphy⁃seal dysplasia tarda(SEDT)of XR,and the c.94 del G,p.D32T,fxX6 of TRAPPC2 is a novel pathogenic mutation that has not been reported,which is the internal cause of the disease,and there is a significant correlation between genotype and phenotype.This study has further enriched the mutation spectrum of TRAPPC2 gene and laid a good foundation for fu⁃ture eugenics and early disease prevention.