Department of Laboratory Medicine, Seoul National University Bundang Hospital, Seongnam, Korea.
Seoul National University College of Medicine, Seoul, Korea.
Mov Disord. 2020 May;35(5):868-876. doi: 10.1002/mds.27998. Epub 2020 Feb 10.
SNCA multiplication is a genomic cause of familial PD, showing dosage-dependent toxicity. Until now, nonallelic homologous recombination was suggested as the mechanism of SNCA duplication, based on various types of repetitive elements found in the spanning region of the breakpoints. However, the sequence at the breakpoint was analyzed only for 1 case.
We have analyzed the breakpoint sequences of 6 patients with PD who had duplicated SNCA using whole-genome sequencing data to elucidate the mechanism of SNCA duplication.
Six patient samples with SNCA duplication underwent whole-genome sequencing. The duplicated regions were defined with nucleotide-resolution breakpoints, which were confirmed by junction polymerase chain reaction and Sanger sequencing. The search for potential non-B DNA-forming sequences and stem-loop structure predictions was conducted.
Duplicated regions ranged from the smallest region of 718.3 kb to the largest one of 4,162 kb. Repetitive elements were found at 8 of the 12 breakpoint sequences on each side of the junction, but none of the pairs shared overt homologies. Five of these six junctions had microhomologies (2-4 bp) at the breakpoint, and a short stretch of sequences was inserted in 3 cases. All except one junction were located within or next to stem-loop structures.
Our study has determined that homologous recombination mechanisms involving repetitive elements are not the main cause of the duplication of SNCA. The presence of microhomology at the junctions and their position within stem-loop structures suggest that replication-based rearrangements may be a common mechanism for SNCA amplification. © 2020 International Parkinson and Movement Disorder Society.
SNCA 倍增是家族性 PD 的一种基因组病因，表现出剂量依赖性毒性。到目前为止，基于在断点跨越区发现的各种类型重复元件，非等位基因同源重组被认为是 SNCA 重复的机制。然而，仅对 1 例患者的断点序列进行了分析。
我们使用全基因组测序数据分析了 6 例具有 SNCA 重复的 PD 患者的断点序列，以阐明 SNCA 重复的机制。
对 6 例 SNCA 重复的患者样本进行全基因组测序。使用核苷酸分辨率断点定义重复区域，通过连接聚合酶链反应和 Sanger 测序确认。对潜在非 B DNA 形成序列和茎环结构预测进行了搜索。
重复区域的范围从最小的 718.3 kb 到最大的 4162 kb。在每个连接点两侧的 12 个断点序列中的 8 个序列中发现了重复元件，但没有一对具有明显的同源性。这 6 个连接点中有 5 个在断点处具有微同源性（2-4 个碱基），在 3 个病例中插入了一小段序列。除一个连接点外，所有连接点都位于茎环结构内或附近。
我们的研究表明，涉及重复元件的同源重组机制不是 SNCA 重复的主要原因。连接点处微同源性的存在及其在茎环结构内的位置表明，基于复制的重排可能是 SNCA 扩增的一种常见机制。© 2020 国际帕金森病和运动障碍学会。
