X-连锁迟发性脊髓骨骺发育不良家系的基因诊断

目的 探讨一个X-连锁迟发性脊髓骨骺发育不良(X-linked spondyloepiphyseal dysplasia tarda,SEDL)家系发病的分子机制,建立基因诊断方法 .方法 采用身高测量、影像学检查殚及家系分析进行临床诊断.收集相关家系成员的外周血标本.提取基因组DNA后,采用PCR-SSCP和DNA测序分析家系中先证者、携带者和健康人SEDL基因的第3～6外显子.利用微卫星位点DXS16进行连锁分析.结果 PCR-SSCP检测到先证者第4外显子有异常泳动带;第4外显子的序列分析表明3例先证者均存在C.218C＞T突变,导致氨基酸序列S73L改变,3例携带者均存在该核苷酸位点的杂合突变,健康人未见突变;先证者的第3、5和6外显子核酸序列未见突变.序列分析证实家系中3名未婚女性Ⅲ10、Ⅳ6和Ⅳ7为致病基因携带者.结论 C.218C＞T突变是导致该家系发病的分子机制,可采用第4外显子序列分析对该家系进行基因诊断和产前基因诊断.

Gene diagnosis of X-linked spondyloepiphyseal dysplasia tarda

ObjectiveTo investigate the molecular pathogenesis of a pedigree of X-linked spondyloepiphyseal dysplasia atarda (SEDL) and to establish methods of gene diagnosis. Methods Clinical diagnosis was made based on height measurement, radiological examination and pedigree analysis. Peripheral blood samples of relevant family members were collected. After genomic DNA extraction, single strand conformation polymorphism (SSCP) followed with DNA sequencing was used to detect SEDL gene exons 36. Microsatellite marker DXS16 was selected for linkage analysis. Results The abnormal electrophoretic bands were detected in exon 4 of probands by PCR-SSCP. A c. 218C ＞ T mutation in exon 4 of SEDL gene was found in three probands, which resulted in a change in amino acid sequence S37L. The heterozygous exon 4 mutation was identified in three carriers, but not in healthy individuals, and no mutations were detect in exon 3, 5 and 6 of probands. Three unmarried young females (Ⅲ10, Ⅳ6 and Ⅳ7) were found to harbor the mutation by DNA sequencing analysis. ConclusionsA c. 218C ＞ T missense mutation in exon 4 of SEDL gene is the cause of molecular pathogenesis of the pedigree. SSCP and DNA sequencing can be used for prenatal gene diagnosis.