RNAseq of brain tissue derived from mouse model of neurodegenerative disorder treated with antisense oligonucleotides

The Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is neurodegenerative disorder caused by expansion of CGG repeats (CGGexp) in 5' untranslated region of FMR1 gene encoding FMRP protein. The CGGexp-induced biosynthesis and accumulation of the aggregated form of polyglycine protein (FMRpolyG), which is a product of Repeat-Associated Non-AUG translation of long CGG repeats is considered to be main factor triggering neurodegenerative processes in FXTAS patients. Since the causative molecular targets are well defined, FXTAS is highly amenable to the development of RNA targeting therapy. We showed high efficiency of antisense oligonucleotides (ASOs) as potential therapeutic agent. Short ASOs composed of locked nucleic acid residues bind along the CGGexp RNA (rCGGexp) with very high affinity both in vitro and in vivo. These ASOs were delivered directly into cerebrospinal fluid in brain of mouse model expressing the transgene with 90 CGG repeats exclusively in neural cells. Importantly, reduction of FMRpolyG intranuclear inclusions in the cerebellum positively correlates with behavioral features of FXTAS in treated animals. Moreover, gene expression analysis and gene ontology classification performed basing on RNAseq results showed significant correction of ASOs treated FXTAS mice towards control mice. Our data demonstrate that short ASOs rescue effects of toxic rCGGexp and can be considered as therapeutic strategy in FXTAS.

脆性X相关震颤/共济失调综合征（Fragile X-associated Tremor/Ataxia Syndrome, FXTAS）是一类神经退行性疾病，由编码FMRP蛋白的FMR1基因5'非翻译区内的CGG重复序列扩增（CGGexp）所引发。长CGG重复序列通过重复相关非AUG翻译生成聚甘氨酸蛋白（FMRpolyG），CGGexp可诱导该蛋白的生物合成与聚集，这一过程被认为是触发FXTAS患者神经退行性病变的核心致病因素。鉴于其致病分子靶点已明确，FXTAS极适合开展RNA靶向治疗的研发。本研究证实反义寡核苷酸（antisense oligonucleotides, ASOs）作为潜在治疗制剂的高效性：由锁核酸残基构成的短链ASOs可在体外与体内均以极高亲和力结合CGGexp RNA（rCGGexp）。此类ASOs被直接注入仅在神经细胞中表达携带90个CGG重复序列转基因的小鼠模型的脑脊液中。值得注意的是，经治疗小鼠小脑内FMRpolyG核内包涵体的减少量，与FXTAS相关行为学特征呈显著正相关。此外，基于RNA测序结果开展的基因本体分类分析显示，接受ASOs治疗的FXTAS小鼠的基因表达谱已向对照组小鼠发生显著校正。本研究数据表明，短链ASOs可挽救毒性rCGGexp所介导的损伤，有望成为FXTAS的治疗策略。