Stockholm University, Department of Biochemistry and Biophysics, Svante Arrhenius väg 16C, 10691 Stockholm, Sweden.
Stockholm University, Department of Biochemistry and Biophysics, Svante Arrhenius väg 16C, 10691 Stockholm, Sweden.
Mol Cell Neurosci. 2021 Jan;110:103584. doi: 10.1016/j.mcn.2020.103584. Epub 2020 Dec 16.
Polyglutamine (polyQ) diseases, such as Spinocerebellar ataxia type 7 (SCA7), are caused by expansions of polyQ repeats in disease specific proteins. The sequestration of vital proteins into aggregates formed by polyQ proteins is believed to be a common pathological mechanism in these disorders. The RNA-binding protein FUS has been observed in polyQ aggregates, though if disruption of this protein plays a role in the neuronal dysfunction in SCA7 or other polyQ diseases remains unclear. We therefore analysed FUS localisation and function in a stable inducible PC12 cell model expressing the SCA7 polyQ protein ATXN7. We found that there was a high degree of FUS sequestration, which was associated with a more cytoplasmic FUS localisation, as well as a decreased expression of FUS regulated mRNAs. In contrast, the role of FUS in the formation of γH2AX positive DNA damage foci was unaffected. In fact, a statistical increase in the number of γH2AX foci, as well as an increased trend of single and double strand DNA breaks, detected by comet assay, could be observed in mutant ATXN7 cells. These results were further corroborated by a clear trend towards increased DNA damage in SCA7 patient fibroblasts. Our findings suggest that both alterations in the RNA regulatory functions of FUS, and increased DNA damage, may contribute to the pathology of SCA7.
多聚谷氨酰胺（polyQ）疾病，如脊髓小脑共济失调 7 型（SCA7），是由疾病特异性蛋白中 polyQ 重复序列的扩展引起的。聚谷氨酰胺蛋白形成的聚集体中重要蛋白的隔离被认为是这些疾病的共同病理机制。RNA 结合蛋白 FUS 已在 polyQ 聚集体中观察到，尽管该蛋白的破坏是否在 SCA7 或其他 polyQ 疾病的神经元功能障碍中起作用尚不清楚。因此，我们在稳定诱导的 PC12 细胞模型中分析了表达 SCA7 polyQ 蛋白 ATXN7 的 FUS 定位和功能。我们发现存在高度的 FUS 隔离，这与更细胞质 FUS 定位以及 FUS 调节的 mRNA 表达减少有关。相比之下，FUS 在 γH2AX 阳性 DNA 损伤焦点形成中的作用不受影响。事实上，在突变 ATXN7 细胞中，可以观察到 γH2AX 焦点数量的统计学增加，以及彗星分析检测到的单链和双链 DNA 断裂的增加趋势。这些结果进一步得到 SCA7 患者成纤维细胞中明显增加的 DNA 损伤趋势的证实。我们的研究结果表明，FUS 的 RNA 调节功能的改变以及增加的 DNA 损伤都可能导致 SCA7 的病理。
