[Analysis of Abnormal Genotyping at Amelogenin Locus in Male Individuals].

内容摘要

To investigate the abnormal genotyping and its causes at the Amelogenin locus in male samples. A total of 23 647 blood samples from unrelated male individuals were analyzed using the STRtyper-21G kit, and 38 samples with abnormal Amelogenin locus were identified. These samples were retested and classified using GlobalFilerTM and PowerPlex® 21 kits. Additional sex chromosome STR genotyping and Sanger sequencing were performed for samples with abnormal genotypes. Sequence-tagged site (STS) testing was conducted for samples suspected of Amel-Y microdeletions. Among above 38 samples, except for Amelogenin locus, all samples showed normal male sex chromosome STR typing. The detection rate of abnormal genotyping was 0.161% (38/23 647), which were categorized into three major types. Among them, 30 cases had Amel-X deletion: 5 cases had C→T mutation at position 372; 2 cases had G→A mutation at position 293; 23 cases had A→G mutation at position 304. There were 2 cases of Amel-Y deletion: 1 case of insertion mutation of TTAA at position 387, and 1 case of microdeletion of the short arm containing Amel-Y. Six cases of abnormal Amel-X/Y peak ratios were identified: using the STRtyper-21G kit, the abnormalities appeared as low Amel-X with absent Amel-Y, normal Amel-X with absent Amel-Y, normal Amel-X with low Amel-Y, respectively. However, retesting with GlobalFilerTM and PowerPlex® 21 kits consistently showed normal Amel-X with low Amel-Y. The GlobalFilerTM profiling showed that the peak heights of Amel-Y were comparable to those of the Y-InDel and DYS391 markers, and no abnormalities were detected by sequencing. Amelogenin genotyping abnormalities occur at a measurable frequency in the population and are mainly associated with mutations, which can be categorized as Amel-X deletion, Amel-Y deletion, and Amel-X/Y peak ratio abnormality. Regarding normal Amel-X peaks with lower Amel-Y peaks, the possibility of mosaic loss of chromosome Y (mLOY) in samples, which is commonly observed in elderly males, should be considered and given attention. 目的: 探讨男性样本Amelogenin基因座的异常分型及原因。方法: 用STRtyper-21G试剂盒对 23 647例男性无关个体血样进行检验，筛选出Amelogenin基因座分型异常的样本共38例。用GlobalFilerTM、PowerPlex® 21试剂盒复核并对结果分类;对分型异常样本，补充性染色体STR分型和Sanger测序;对疑似Amel-Y微缺失样本，进行序列标签位点检测。结果: 上述38例样本，除Amelogenin基因座外，其他性染色体STR分型结果均正常。Amelogenin基因座分型异常样本检出率为0.161%（38/23 647）。38例分型异常样本可分为3大类，其中，Amel-X缺失30例:5例在第372位发生了C→T突变，2例在第293位发生了G→A突变，23例在第304位发生了A→G突变;Amel-Y缺失2例:1例在第387位发生了TTAA的插入突变，1例包含Amel-Y的短臂微缺失;Amel-X/Y峰高比异常6例:STRtyper-21G试剂盒表现分别为Amel-X峰偏低、Amel-Y峰缺失，Amel-X峰正常、Amel-Y峰缺失，Amel-X峰正常、Amel-Y峰偏低，而GlobalFilerTM、PowerPlex® 21复核结果均表现为Amel-X峰正常、Amel-Y峰偏低，且GlobalFilerTM分型中Amel-Y峰高与Y-InDel、DYS391峰高相当，测序未发现异常。结论: Amelogenin基因座分型异常在人群中占有一定比例，多与突变有关，可分为Amel-X缺失、Amel-Y缺失、Amel-X/Y峰高比异常。对于Amel-X峰正常、Amel-Y峰偏低分型，应考虑样本存在Y染色体嵌合缺失（mosaic loss of chromosome Y，mLOY）的可能（多见于老年男性个体），应引起重视。.