应用多种遗传标记甄别全同胞和半同胞关系1例

Application of Multiple Genetic Markers in Determination of Full and Half Sibling Relationship:A Case Report

目的通过对1例全同胞关系存疑案例的鉴定,探讨多种遗传标记的综合使用在甄别同胞关系中的应用。方法提取4名受检者(张1、张2,男性;张3、张4,女性)血痕DNA,使用EX20STR试剂盒扩增检验常染色体基因座,X19试剂盒扩增检验X-STR基因座,DataY24STR试剂盒扩增检验Y-STR基因座,一代测序技术分析线粒体DNA高变区Ⅰ和Ⅱ的SNP多态性。结果基于常染色体STR基因分型的IBS评分结果提示:张2、张3、张4之间存在全同胞关系,无法判断张1与张2、张3、张4之间的全同胞关系;基于常染色体STR基因分型的ITO法、判别函数法计算结果,支持张2、张3、张4之间存在全同胞关系,提示张1与张2、张3、张4存在半同胞关系;依据X-STR基因分型和线粒体DNA高变区检测结果,提示张1、张2、张3、张4为同一生母,同时Y-STR基因分型结果排除张1与张2为同一生父,进一步支持张1与张2、张3、张4为同母异父半同胞关系,并得到根据常染色体STR基因分型结果重建父母基因型的验证。结论对于同胞关系鉴定,需要综合应用各种遗传标记(包括常染色体STR、性染色体STR、线粒体DNA序列等),综合使用各种分析方法(包括IBS评分、ITO法、判别函数法和家系重建等),互相验证和支持,才能获得可靠的鉴定意见。

Objective To investigate the application of the comprehensive use of multiple genetic markers in full and half sibling relationship testing through the identification of a case of suspected sibling relationship. Methods Genomic DNA were extracted from bloodstain samples from 4 subjects(ZHANG-1, ZHANG-2, male;ZHANG-3, ZHANG-4, female). Autosomal STR loci, X-STR, Y-STR loci and polymorphisms of mtDNA HV-Ⅰ and Ⅱwere genotyped by EX20 STR kit, X19 kit, Data Y24 STR kit, and Sanger sequencing, respectively. Results According to autosomal STR based IBS scoring results, full sibling relationships were indicated among ZHANG-2, ZHANG-3 and ZHANG-4, but those were not indicated between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4. According to autosomal STR based FSI and HSI, with ITO method and discriminant function method, full sibling relationships among ZHANG-2, ZHANG-3 and ZHANG-4 were indicated, and half sibling relationships between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4 were also indicated. X-STR and mtDNA sequencing results showed that all the 4 samples came from a same maternal line, and Y-STR results showed that ZHANG-1 and ZHANG-2 did not come from a same paternal line, which supported the half sibling relationship between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4, verified by parental genotype reconstruction based on autosomal STR genotyping. Conclusion For the identification of sibling relationships, it is effective to have reliable results with the mutual verification and support of multiple genetic markers (autosomal STR, sex chromosomal STR and mtDNA sequence) and calculations (IBS, ITO, discriminant function method and family reconstruction).