Department of Clinical Genetics, Erasmus University Medical Center-Sophia Children's Hospital, 3000 CA Rotterdam, The Netherlands.
Department of Pediatric Surgery, Erasmus University Medical Center-Sophia Children's Hospital, 3000 CA Rotterdam, The Netherlands.
Int J Mol Sci. 2021 Nov 16;22(22):12354. doi: 10.3390/ijms222212354.
Patients with Hirschsprung disease (HSCR) do not always receive a genetic diagnosis after routine screening in clinical practice. One of the reasons for this could be that the causal mutation is not present in the cell types that are usually tested-whole blood, dermal fibroblasts or saliva-but is only in the affected tissue. Such mutations are called somatic, and can occur in a given cell at any stage of development after conception. They will then be present in all subsequent daughter cells. Here, we investigated the presence of somatic mutations in HSCR patients. For this, whole-exome sequencing and copy number analysis were performed in DNA isolated from purified enteric neural crest cells (ENCCs) and blood or fibroblasts of the same patient. Variants identified were subsequently validated by Sanger sequencing. Several somatic variants were identified in all patients, but causative mutations for HSCR were not specifically identified in the ENCCs of these patients. Larger copy number variants were also not found to be specific to ENCCs. Therefore, we believe that somatic mutations are unlikely to be identified, if causative for HSCR. Here, we postulate various modes of development following the occurrence of a somatic mutation, to describe the challenges in detecting such mutations, and hypothesize how somatic mutations may contribute to 'missing heritability' in developmental defects.
在临床实践中，并非所有先天性巨结肠症（HSCR）患者在常规筛查后都能得到基因诊断。造成这种情况的原因之一可能是，致病突变并不存在于通常检测的细胞类型中——全血、皮肤成纤维细胞或唾液，但只存在于受影响的组织中。这种突变被称为体细胞突变，它可以在受孕后任何发育阶段的特定细胞中发生。然后，这些突变将存在于所有后续的子细胞中。在这里，我们研究了 HSCR 患者体细胞突变的存在情况。为此，我们对同一患者的纯化肠神经嵴细胞（ENCC）和血液或成纤维细胞中的 DNA 进行了全外显子组测序和拷贝数分析。随后通过 Sanger 测序对鉴定出的变体进行了验证。在所有患者中都发现了几种体细胞变体，但在这些患者的 ENCC 中并未特异性鉴定出导致 HSCR 的突变。也未发现较大的拷贝数变异是 ENCC 所特有的。因此，如果体细胞突变是导致 HSCR 的原因，我们认为不太可能被识别。在这里，我们提出了体细胞突变发生后各种可能的发育模式，以描述检测这些突变的挑战，并假设体细胞突变如何导致发育缺陷中的“遗传缺失”。
