Departments of Laboratory Medicine.
Ophthalmology, Seoul National University Hospital, Seoul National University College of Medicine.
J Glaucoma. 2020 May;29(5):331-336. doi: 10.1097/IJG.0000000000001466.
PRéCIS:: One (0.2%) of 418 Korean normal-tension glaucoma (NTG) patients had TBK1 duplication. The putative mechanism of TBK1 duplication in Korean NTG patients is the nonhomologous end-joining.
TBK1 duplication is a genomic cause of familial NTG. NTG accounts for up to 90% of primary open-angle glaucoma in Koreans, with genetic tendency. We aimed to investigate the prevalence of TBK1 duplication in Korean NTG patients and to identify their genomic structure and duplication mechanism.
We obtained DNA samples from 418 NTG patients and 195 healthy controls for evaluating TBK1 copy number variations using a semiquantitative polymerase chain reaction (PCR). The samples with TBK1 gene duplication were further confirmed using droplet digital PCR. The whole-genome sequencing of patient samples with duplications was performed to identify the accurate breakpoints and to elucidate the genomic structure. Ophthalmic evaluation and confirmation of TBK1 duplication using junction PCR were performed in families of positive patients.
TBK1 duplication was found in 1 of 418 NTG cases (0.2%). The duplication range was from g.64,803,151 to g.64,927,214 (124,063 bp). It is the smallest region of overlapping duplication in TBK1. Any repetitive sequences were not found near the breakpoints of our case. Inserted sequences were found within the breakpoints. A brother and a niece of the positive case appeared the typical clinical features of NTG and shared the same TBK1 duplications with the index case.
In Korea, the prevalence of TBK1 duplication was 0.2% and the smallest reported TBK1 duplication associated with NTG was found. The mechanism of TBK1 duplication was suggested to be nonhomologous end-joining while a previous report pointed out the mechanism of TBK1 duplications as nonallelic homologous recombination.
TBK1 重复是家族性正常眼压性青光眼（NTG）的一种基因组病因。NTG 占韩国原发性开角型青光眼的 90%，具有遗传倾向。我们旨在调查韩国 NTG 患者中 TBK1 重复的发生率，并确定其基因组结构和重复机制。
我们从 418 名 NTG 患者和 195 名健康对照者中获得 DNA 样本，使用半定量聚合酶链反应（PCR）评估 TBK1 拷贝数变异。使用液滴数字 PCR 进一步确认具有 TBK1 基因重复的样本。对具有重复的患者样本进行全基因组测序，以确定准确的断点，并阐明基因组结构。对阳性患者的家族进行眼科评估和 TBK1 重复确认，使用连接 PCR。
在 418 例 NTG 病例中发现 1 例（0.2%）TBK1 重复。重复范围为 g.64,803,151 至 g.64,927,214（124,063bp）。这是 TBK1 中重叠重复的最小区域。在我们的病例断点附近未发现任何重复序列。在断点内发现插入序列。阳性病例的一个兄弟和一个侄女出现了典型的 NTG 临床特征，并与索引病例共享相同的 TBK1 重复。
在韩国，TBK1 重复的发生率为 0.2%，发现了与 NTG 相关的最小 TBK1 重复。TBK1 重复的机制被认为是非同源末端连接，而之前的报告指出 TBK1 重复的机制是非等位基因同源重组。
