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

阿尔茨海默病(AD)是一种衰弱和普遍的神经退行性疾病，没有有效的 预计在未来30年内，患病率将翻一番。最早的标志之一 AD是突触丢失，随后是淀粉样β聚集和tau神经原纤维缠结。这些步骤 导致这些聚集事件，特别是在晚发性AD患者中，人们对此知之甚少。 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 并进行了高通量的RNA测序。我们发现不同的是 阿尔茨海默病患者突触相关基因的表达及其与突触转运和 局部信使核糖核酸的翻译。值得注意的是，在询问非编码转录组时，我们发现了一种广泛的 环状核糖核酸的分布从细胞体向突触的转移。CircRNA是稳定的 由保守的后剪接外显子连接的共价键形成的分子可以与 线性对应物。有趣的是，在最高差异表达的CircRNA中，有两个来自 Gsk3β在AD中经历了从一种亚型显著上调到另一种亚型的转换 监管下调。Gsk3β对tau的磷酸化是其聚集所必需的，而gsk3β抑制剂有 被作为AD的翻译目标积极追求。对Gsk3β和其他环状RNA的进一步评价 在一个大型RNAseq库中发现了外显子周围PSEN中差异表达的CircRNAs 与低氧介导的选择性剪接有关。因此，AD相关的关键蛋白都有RNA 突触的对应物是差异表达的，可能具有关键的调节作用。我们的 研究结果指出了在RNA水平上的一种新的调控模式。通过一系列的体外研究和 在tau病理的小鼠模型上，我们建议从治疗的角度调节CircGSK3B和CircGSK3B的表达 CircPSEN2亚型以恢复tau的适当调节。我们建议确定监管机构是否 可选择的gsk3β外显子周围的特征影响环状rna的产生，以及rna解旋酶 影响我们观察到的GSK3β环状RNA异构体开关。此外，我们还将评估两国关系 PSEN环状RNA的生物发生与氧化应激对异常PSEN_2的影响 选择性剪接-我们观察到的一种现象在散发性AD中显著丰富。总而言之， 我们将利用我们对CircRNA生物发生和调节规则的理解来产生 能够保持Gsk3β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.