Mechanisms underlying circular RNA biogenesis in Alzheimer’s disease related genes

阿尔茨海默病（AD）是一种使人衰弱的和广泛的神经退行性疾病， 预计在未来30年内患病率将翻一番。早期的标志之一 AD是突触丢失，随后是淀粉样蛋白β聚集和tau神经元缠结。的步骤 导致这些聚集事件，特别是在晚发性AD患者中，尚不清楚。 为了更好地理解与突触丢失相关的转录机制，我们分离了突触， 并进行高通量RNA测序。我们发现 表达与AD患者突触相关的mRNA，暗示突触转运， 局部mRNA翻译。值得注意的是，当询问非编码转录组时，我们发现了一个广泛的 环状RNA（circRNA）从细胞体到突触的分布转移。CircRNA稳定 由保守的反向剪接外显子连接的共价键形成的分子， 线性对应物有趣的是，在差异表达最高的circRNA中，有两种circRNA来自 GSK 3 β在AD中从一种亚型显著上调至另一种亚型， 下调。tau蛋白的GSK 3 β磷酸化对其聚集是必需的，并且GSK 3 β抑制剂具有以下作用： 作为AD的翻译靶点被积极追求。GSK 3 β和其他环状RNA的进一步评价 在一个大型RNAseq库中发现了PSEN 2外显子周围差异表达的circRNA， 与缺氧介导的选择性剪接有关。因此，关键的AD相关蛋白具有RNA 在突触处的差异表达的对应物可能具有关键的调节作用。我们 研究结果指出了RNA水平上的一种新的调控模式。通过一系列体外研究， 在tau病理学的小鼠模型中，我们提出治疗性调节circGSK 3B的表达， circPSEN 2同种型恢复tau的适当调节。我们建议确定监管机构是否 GSK 3 β外显子周围的特征影响circRNA的产生，以及RNA解旋酶是否 影响我们观察到的GSK 3 β circRNA亚型转换。此外，我们还将评估 PSEN 2 circRNA生物发生与氧化应激在影响异常PSEN 2中的作用之间的关系 选择性剪接-我们观察到在散发性AD中显著富集的现象。总的来说， 我们将利用我们对circRNA生物发生和调控规则的理解， 能够保持GSK 3 β的适当表达并防止tau聚集的分子。

Alzheimer’s disease (AD) is a debilitating and pervasive neurodegenerative disorder with no effective treatments and is predicted to double in prevalence over the next 30 years. One of the first hallmarks of AD is loss of synapses followed by amyloid beta aggregation and tau neurofibrillary tangles. The steps leading to these aggregation events, especially in individuals with late-onset AD, are poorly understood. To better comprehend the transcriptional mechanisms associated with synapse loss, we isolated synapses in the form of synaptosomes and performed high throughput RNA sequencing. We found differentially expressed mRNAs associated with the synapse in AD patients with implications for synaptic transport and local mRNA translation. Notably, when interrogating the noncoding transcriptome, we found a widespread shift of distribution of circular RNAs (circRNAs) from cell bodies to synapses. CircRNAs are stable molecules formed from covalent linkages of conserved back-spliced exon junctions that can compete with linear counterparts. Interestingly among the top differentially expressed circRNAs were two circRNAs from GSK3β, which underwent a switch from one isoform significantly upregulated in AD to another significantly downregulated. GSK3β phosphorylation of tau is essential for its aggregation and GSK3β inhibitors have actively been pursued as translational targets for AD. Further evaluation of GSK3β and other circular RNAs in a large RNAseq repository revealed differentially expressed circRNAs in PSEN2 surrounding exons associated with hypoxia mediated alternative splicing. Therefore, key AD associated proteins have RNA counterparts at the synapse that are differentially expressed that may have critical modulatory roles. Our findings point to a novel mode of regulation at the RNA level. Through a series of in vitro studies and mouse models of tau pathology, we propose to therapeutically modulate the expression of circGSK3B and circPSEN2 isoforms to restore appropriate regulation of tau. We propose to ascertain whether regulatory features surrounding alternative GSK3β exons affect circRNA production and whether RNA helicases influence the GSK3β circRNA isoform switch that we observe. In addition, we will evaluate the relationship between PSEN2 circRNA biogenesis and the role of oxidative stress in affecting aberrant PSEN2 alternative splicing – a phenomenon we observe to be significantly enriched in sporadic AD. Collectively, we will leverage our understanding of the rules governing circRNA biogenesis and regulation to generate molecules capable of preserving appropriate expression of GSK3β and prevent tau aggregation.