Decreasing Mutant ATXN1 Nuclear Localization Improves a Spectrum of SCA1-Like Phenotypes and Brain Region Transcriptomic Profiles. Decreasing Mutant ATXN1 Nuclear Localization Improves a Spectrum of SCA1-Like Phenotypes and Brain Region Transcriptomic Profiles

Spinocerebellar ataxia type 1 (SCA1) is a dominant trinucleotide repeat neurodegenerative disease characterized by motor dysfunction, cognitive impairment, and premature death. Degeneration of cerebellar Purkinje cells is a frequent and prominent pathological feature of SCA1. We previously showed that transport of ATXN1 to Purkinje cell nuclei is required for pathology, where mutant ATXN1 alters transcription. To examine the role of ATXN1 nuclear localization broadly in SCA1-like disease pathogenesis, CRISPR-Cas9 was used to develop a mouse with an amino acid alteration (K772T) in the nuclear localization sequence of the expanded ATXN1 protein. Characterization of these mice indicates proper nuclear localization of mutant ATXN1 contributes to many disease-like phenotypes including motor dysfunction, cognitive deficits, and premature lethality. RNA sequencing analysis of genes with expression corrected to WT levels in Atxn1175QK772T/2Q mice indicates that transcriptomic aspects of SCA1 pathogenesis differ between the cerebellum, brainstem, cerebral cortex, hippocampus, and striatum. Overall design: Genetic expression profile comparison (RNA sequencing) of WT, Atxn1175QK772T/2Q, and Atxn1175Q/2Q mouse cerebellum, brainstem, cortex, hippocampus, and striatum at 10 weeks of age and cerebellum, medulla, cortex, hippocampus, and striatum at 26 weeks of age. N=4 mice per genotype at each age.

1型脊髓小脑共济失调（Spinocerebellar ataxia type 1, SCA1）是一类显性遗传的三核苷酸重复相关性神经退行性疾病，以运动功能障碍、认知损害及过早死亡为典型临床特征。小脑浦肯野细胞（Purkinje cell）的变性是SCA1最为常见且突出的病理特征。本课题组前期研究证实，ATXN1向浦肯野细胞核的转运是疾病致病的必要环节，突变型ATXN1可在细胞核内异常调控基因转录。
为全面探究ATXN1核定位在类SCA1疾病发病机制中的作用，研究人员利用CRISPR-Cas9基因编辑技术构建了一株小鼠模型，该模型的扩增型ATXN1蛋白的核定位序列中存在一处氨基酸改变（K772T）。
对该小鼠模型的表型分析结果表明，突变型ATXN1的正常核定位可诱导多种疾病样表型，包括运动功能障碍、认知缺陷以及过早死亡。
对Atxn1^175QK772T/2Q小鼠中表达水平恢复至野生型（Wild Type, WT）的基因进行RNA测序分析后发现，SCA1发病机制的转录组学特征在小脑、脑干、大脑皮层、海马体与纹状体中存在显著差异。
本研究的总体实验设计如下：对10周龄和26周龄的野生型、Atxn1^175QK772T/2Q及Atxn1^175Q/2Q三种基因型小鼠的不同脑区组织开展基因表达谱比较（RNA测序）；其中10周龄小鼠采集的脑区为小脑、脑干、大脑皮层、海马体及纹状体，26周龄小鼠采集的脑区为小脑、延髓、大脑皮层、海马体及纹状体；每个年龄组、每种基因型的小鼠样本量均为4只。