Monozygotic twins are assumed to have identical genomes. Based on this assumption, phenotypic discordance in monozygotic twins has been previously attributed to environmental factors. However, recent genomic studies have identified characteristic somatic mutations in monozygotic twins discordant for Darier disease, Van der Woude syndrome, and Dravet syndrome. Here, we explored somatic mutations in four pairs of monozygotic twins discordant for schizophrenia or delusional disorder. We analyzed whole exome sequence data obtained from blood samples and identified seven somatic mutations in one twin pair discordant for delusional disorder. All seven of these mutations were validated by independent amplicon sequencing, and five of them were further validated by pyrosequencing. One somatic mutation in the patient with delusional disorder showed a missense variant in ABCC9 with an allele fraction of 7.32%. Although an association between the somatic mutations and phenotypic discordance could not be established conclusively in this study, our results suggest that somatic mutations in monozygotic twins may contribute to the development of psychiatric disorders, and can serve as high-priority candidates for genetic studies.

假定单卵双胞胎具有相同的基因组。基于此假设，单卵双胞胎中的表型不一致先前已归因于环境因素。但是，最近的基因组研究已经发现，单卵双胞胎中的特征性体细胞突变与Darier病，Van der Woude综合征和Dravet综合征不一致。在这里，我们探讨了四对精神分裂症或妄想症不一致的单卵双胞胎的体细胞突变。我们分析了从血液样本中获得的全外显子组序列数据，并在一对错觉失调的双胞胎对中发现了七个体细胞突变。通过独立的扩增子测序验证了所有这七个突变，并通过焦磷酸测序进一步验证了其中五个。等位基因分数为7.32％的ABCC9。尽管无法在本研究中最终确定体细胞突变与表型不一致之间的关联，但我们的研究结果表明，单卵双胞胎中的体细胞突变可能有助于精神疾病的发展，并且可以作为遗传学研究的优先对象。