Contribution of BIN1 and Synj1 to endosomal pathogenesis Alzheimer's Disease and Down Syndrome

阿尔茨海默氏症预计将是未来几十年最重要的全球健康风险之一 目前还没有有效的预防或改变疾病的疗法。该领域的主要关注点是 一直致力于减少突触毒素β-肽(A-β)，然而，最近的晚期临床试验 已经被证明是令人失望的。因此，需要新的战略和细胞目标。最近的研究发现 参与内吞作用的基因变异，如桥接整合子1(BIN1或两栖动物蛋白 2/AMPH2)和磷脂酰肌醇结合蛋白组装蛋白(PICALM)与AD风险相关。vbl.使用 串联合体的生物信息学分析；基因邻域；基因融合；基因共现； 表达、实验数据、数据库、文本挖掘和蛋白质同源性表明BIN1被预测为 在功能上与PICALM相互作用，关键是，Synaptojanin1(Synj1)。Synj1是一种富含在 去磷酸化关键信号脂质磷脂酰肌醇-4，5-二磷酸的大脑[P(4，5)P2]。 已知对神经元功能至关重要的磷脂酰肌醇，已经被我们的小组和其他人证明是 在阿尔茨海默病患者的大脑和小鼠模型中都发生了变化。Synj1是PI(4，5)P2维护的核心 突触和我们已经证明，Synj1的一个拷贝的丢失已经被证明可以消除Aβ诱导的 突触功能障碍。AD和DS表现出类似的病理，其中APP处理和Aβ是核心。戴斯 个体是APP和Synj1以及Synj1调节激酶DYRK1A的三体，是罹患 开发AD。Synj1已被证明可以改善DS小鼠模型的内体功能障碍。当前的研究 已经确定来自DS患者的IPSC来源的神经元具有类似的AD的致病特征 包括增加Aβ42的产量和降低Aβ40：Aβ42的比率。然而，神经元分化 显示正常的神经元转化动力学，尽管一项研究观察到夸大的胶质细胞产生， 与DS相关的表型。因此，我们假设Synj1可能是修改突触和 阿尔茨海默病和弥漫性痴呆的内脏病理改变。我们将检验Synj1异常表达和功能的假设 在神经元中，表型可概括为人诱导多能干细胞(IPSC)的内体功能障碍 衍生的神经元。散发性AD和DS的IPSC将分化为前脑神经元。表型 被证明是由Synj1介导的，将在包括内体在内的人类功能神经元中重现 形态和功能、脊柱形态、脂质失调和与BIN1的功能复合体的形成， Picalm和Dyrk1a。CRISPR/Cas9将用于敲除AD和DS三体系中的Synj1等位基因 确定Synj1对异常表型的必要性。此外，新的细胞靶标极有可能 来自相应的IPSC衍生神经元的脂质学和RNAseq研究。我们还将 开发关键的人类神经细胞模型，以适应未来的治疗发展。

Alzheimer's disease is predicted to be one of the highest priority global health risks in coming decades, yet there are currently no effective prophylactic or disease modifying therapies. The primary focus in the field has been to target reduction of the synaptotoxic amyloid β-peptide (Aβ) however, recent late-stage clinical trials have proven disappointing. Therefore, new strategies and cellular targets are required. Recent work has found that genetic variants of genes involved in endocytosis such as Bridging Integrator 1 (BIN1 or amphiphysin 2/AMPH2) and phosphatidylinositol-binding clathrin assembly protein (PICALM) correlate with AD risk. Using bioinformatics analysis of STRING Consortium, gene neighborhood, gene fusions, gene co-occurrence, co- expression, experimental data, databases, text mining and protein homology indicate BIN1 is predicted to interact functionally with PICALM and critically, Synaptojanin1 (Synj1). Synj1 is a lipid phosphatase enriched in brain which dephosphorylates the critical signaling lipid phosphatidylinositol-4,5-bisphosphate [P(4,5)P2]. Phosphoinositides, known to be critical for neuronal function, have been shown by our group and others to be altered in AD affected patient brain as well as in mouse models. Synj1 is central to PI(4,5)P2 maintenance at the synapse and we have shown that loss of one copy of Synj1 has been shown to abrogate Aβ-induced synaptic dysfunction. AD and DS show similar pathologies in which APP processing and Aβ is central. DS individuals are trisomic for APP and Synj1, and Synj1 regulatory kinase DYRK1A and are at high-risk for developing AD. Synj1 has been shown to modify endosomal dysfunction in DS mouse models. Current studies have determined that iPSC derived neurons from DS individuals share similar pathogenic hallmarks of AD including increased Aβ42 production and decreased Aβ40:Aβ42 ratio. However, neuronal differentiation displayed normal neuronal conversion kinetics though one study observed exaggerated glia production, a phenotype associated with DS. Therefore, we hypothesize that Synj1 may be central to modifying synaptic and endosomal pathologies in AD and DS. We will test the hypothesis that aberrant Synj1 expression and function in neuronal phenotypes can recapitulate endosomal dysfunction in human induced pluripotent stem cell (iPSC) derived neurons. iPSC from sporadic AD and DS will be differentiated into forebrain neurons. Phenotypes shown to be mediated by Synj1 will be recapitulated in functional human neurons including endosome morphology and function, spine morphology, lipid dysregulation and functional complex formation with BIN1, PICALM, and Dyrk1a. CRISPR/Cas9 will be used to knock-out Synj1 alleles in AD and DS trisomic lines to determine necessity of Synj1 for aberrant phenotypes. Further, it is highly likely that novel cellular targets will emerge from corresponding lipidomic and RNAseq studies of functional iPSC derived neurons. We will also develop critical human neuronal cell models amenable to future therapeutic development.