摘要目的:对一个疑似X-连锁迟发性脊椎骨骺发育不良（spondyloepiphyseal dysplasia tarda，SEDT）的家系进行临床特征分析和致病基因的筛查，并对可疑变异进行分析，为遗传咨询和产前诊断提供实验依据。方法:采集家系成员病史，一般体检，关节、脊椎X线片检查；收集该家系成员外周血样，提取样本DNA，采用靶向基因高通量测序方法对先证者DNA全外显子进行测序，并对测序数据进行分析；针对可疑突变，采用PCR和Sanger测序对家系其他成员DNA样本进行验证；提取家系成员外周血淋巴细胞的RNA，RT-PCR扩增致病基因外显子3、4区域，琼脂糖凝胶鉴定扩增片段大小；并采用qPCR检测致病基因的表达。结果:根据家系中患者临床表型和脊椎X线片特征，将该家系患者诊断为X-连锁隐性遗传SEDT。全外显子测序检测到先证者转运蛋白复合体亚单位2（trafficking protein particle complex subunit 2， TRAPPC2）基因NM_001011658：c.91A>T（p.K31*）无义突变，其表弟该基因位点也存在相同变异，家系其他无表型成员未检出该变异。患者外周血淋巴细胞RT-PCR结果与家系正常对照的扩增片段相同，表明该变异不影响转录本的剪接。qPCR结果显示，家系患者 TRAPPC2的转录水平表达较家系正常对照及正常人对照显著降低。 结论:发现 TRAPPC2基因c.91A>T新无义变异，该变异可以导致 TRAPPC2功能丧失，是本家系的致病性变异。

abstractsObjective:To provide experimental evidence for genetic counseling and prenatal diagnosis by analyzing the clinical characteristics, screening and identification of the function of suspicious variants in a X-1inked spondyloepiphyseal dysplasia tarda (SEDT) family.Methods:The family members' medical history, general physical examination, femur, spine X-ray examination were collected. Peripheral blood samples of the family members were collected and DNA was extracted from these samples. Sequencing clinical whole exons of proband DNA by targeted gene high-throughput sequencing method, then analysis sequencing data. The suspicious mutation was confirmed in pedigree members by PCR and Sanger sequencing. Reverse transcription polymerase chain reaction (RT-PCR) experiments of total RNA from blood lymphocytes were performed. The amplification of exons 3 and 4 of the pathogenic gene were amplified and identified by agarose gel. The expression of the pathogenic gene was also detected.Results:Three affected males of the family were diagnosed with SEDT according to their clinical and radiological features. A nonsense mutation in the transport protein particle complex subunit 2 ( TRAPPC2) gene NM_001011658: c.91A>T (p.K31*) was found in the proband using whole exome sequencing. This variation was also detected in his cousin, but not in non-phenotypic members of the family. The RT-PCR result for amplification of exon 3 and 4 of peripheral blood lymphocytes was the same as those of normal controls, indicating that the mutation did not affect the splicing of transcripts. qPCR results showed that the transcriptional expression of TRAPPC2 in patients was significantly lower than that in family normal controls and normal people controls. Conclusion:Identification of the novel nonsense mutation (c.91A>T) in the SEDT family enables early patients screening, carrier detection, genetic counseling, prenatal diagnosis, and clinical prevention and treatment. The detailed genotype/phenotype descriptions contribute to the SEDT mutation spectrum. The study of the function of TRAPPC2 mutation will help to further elucidate the role of sedlin in cartilage.