Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, 2600 Glostrup, Denmark.
Copenhagen Neuromuscular Center, Department of Neurology, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark.
Genes (Basel). 2022 May 28;13(6):970. doi: 10.3390/genes13060970.
Myotonic dystrophy type 1 (DM1) is a multisystemic neuromuscular disorder caused by the expansion of a CTG repeat in the 3'-UTR of , which is transcribed to a toxic gain-of-function RNA that affects splicing of a range of genes. The expanded repeat is unstable in both germline and somatic cells. The variable age at disease onset and severity of symptoms have been linked to the inherited CTG repeat length, non-CTG interruptions, and methylation levels flanking the repeat. In general, the genetic biomarkers are investigated separately with specific methods, making it tedious to obtain an overall characterisation of the repeat for a given individual. In the present study, we employed Oxford nanopore sequencing in a pilot study to simultaneously determine the repeat lengths, investigate the presence and nature of repeat interruptions, and quantify methylation levels in the regions flanking the CTG-repeats in four patients with DM1. We determined the repeat lengths, and in three patients, we observed interruptions which were not detected using repeat-primed PCR. Interruptions may thus be more common than previously anticipated and should be investigated in larger cohorts. Allele-specific analyses enabled characterisation of aberrant methylation levels specific to the expanded allele, which greatly increased the sensitivity and resolved cases where the methylation levels were ambiguous.
肌强直性营养不良 1 型（DM1）是一种多系统神经肌肉疾病，由 3'-UTR 中的 CTG 重复序列扩展引起，该重复序列转录为具有毒性的功能获得性 RNA，影响一系列基因的剪接。扩展的重复序列在生殖细胞和体细胞中均不稳定。疾病发病年龄和症状严重程度的可变性与遗传 CTG 重复长度、非 CTG 中断以及重复侧翼的甲基化水平有关。通常，遗传生物标志物分别用特定方法进行研究，因此很难为特定个体获得重复序列的全面特征。在本研究中，我们采用牛津纳米孔测序在一项试点研究中同时确定重复序列长度，研究重复序列中断的存在和性质，并定量测定 CTG 重复序列侧翼区域的甲基化水平在四名 DM1 患者中。我们确定了重复序列长度，在三名患者中，我们观察到了使用重复引物 PCR 未检测到的中断。因此，中断可能比以前预期的更常见，应该在更大的队列中进行研究。等位基因特异性分析能够对扩展等位基因特有的异常甲基化水平进行特征描述，这极大地提高了灵敏度，并解决了甲基化水平模棱两可的情况。
