Department of Biotechnology, Jozef Stefan Institute, Ljubljana 1000, Slovenia.
Graduate School of Biomedicine, Faculty of Medicine, University of Ljubljana, Ljubljana 1000, Slovenia.
J Cell Sci. 2019 Mar 7;132(5):jcs224303. doi: 10.1242/jcs.224303.
The GGGGCC (GC) repeat expansion mutation in the gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Transcription of the repeat and formation of nuclear RNA foci, which sequester specific RNA-binding proteins, is one of the possible pathological mechanisms. Here, we show that (GC) repeat RNA predominantly associates with essential paraspeckle proteins SFPQ, NONO, RBM14, FUS and hnRNPH and colocalizes with known paraspeckle-associated RNA As formation of paraspeckles in motor neurons has been associated with early phases of ALS, we investigated the extent of similarity between paraspeckles and (GC) RNA foci. Overexpression of (GC) RNA results in their increased number and colocalization with SFPQ-stained nuclear bodies. These paraspeckle-like (GC) RNA foci form independently of the known paraspeckle scaffold, the long non-coding RNA Moreover, the knockdown of SFPQ protein in expansion mutation-positive fibroblasts significantly reduces the number of (GC) RNA foci. In conclusion, (GC) RNA foci have characteristics of paraspeckles, which suggests that both RNA foci and paraspeckles play roles in FTD and ALS, and implies approaches for regulation of their formation.
基因中的 GGGGCC（GC）重复扩展突变是额颞叶痴呆（FTD）和肌萎缩侧索硬化（ALS）最常见的遗传原因。重复序列的转录和核 RNA 焦点的形成，这会隔离特定的 RNA 结合蛋白，是一种可能的病理机制。在这里，我们表明（GC）重复 RNA 主要与必需的核小体蛋白 SFPQ、NONO、RBM14、FUS 和 hnRNPH 相关，并与已知的核小体相关 RNA 焦点共定位。由于运动神经元中核小体的形成与 ALS 的早期阶段有关，我们研究了核小体与（GC）RNA 焦点之间的相似程度。（GC）RNA 的过表达导致其数量增加，并与 SFPQ 染色的核体共定位。这些类似于核小体的（GC）RNA 焦点是独立于已知核小体支架，即长非编码 RNA 的形成。此外，在 扩展突变阳性成纤维细胞中敲低 SFPQ 蛋白会显著减少（GC）RNA 焦点的数量。总之，（GC）RNA 焦点具有核小体的特征，这表明 RNA 焦点和核小体都在 FTD 和 ALS 中发挥作用，并暗示了调节它们形成的方法。
