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

据预测，阿尔茨海默病将是未来几十年最优先的全球健康风险之一， 目前还没有有效的预防或疾病改善疗法。该领域的主要重点是 然而，最近的后期临床试验表明， 令人失望因此，需要新的策略和细胞靶点。最近的研究发现， 参与内吞作用的基因的遗传变体，如桥接整合子1（BIN1或两性蛋白）， 2/AMPH2）和磷脂酰肌醇结合网格蛋白组装蛋白（PICALM）与AD风险相关。使用 STRING Consortium的生物信息学分析，基因邻域，基因融合，基因共现，共 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，关键是与Synaptojanin 1（Synj1）相互作用。Synj1是一种脂质磷酸酶， 脑，使关键信号脂质磷脂酰肌醇-4，5-二磷酸[P（4，5）P2]去磷酸化。 磷酸肌醇，已知对神经元功能至关重要，已经被我们的小组和其他人证明是 在AD影响的患者大脑以及小鼠模型中改变。Synj1是PI（4，5）P2维持的核心， 我们已经证明，失去一个Synj1拷贝可以消除A β诱导 突触功能障碍AD和DS显示出相似的病理学，其中APP加工和A β是中心。DS 个体是APP和Synj1以及Synj1调节激酶DYRK1A的三体，并且处于高风险 发展AD。Synj1已被证明可以改变DS小鼠模型中的内体功能障碍。目前的研究 已经确定来自DS个体的iPSC衍生的神经元具有与AD相似的致病特征 包括A β 42产生增加和A β 40：A β 42比率降低。然而，神经元分化 显示正常的神经元转换动力学，尽管一项研究观察到过度的神经胶质产生， 与DS相关的表型。因此，我们假设Synj1可能是调节突触和突触后神经元的核心。 AD和DS中的内体病理学。我们将检验Synj1的异常表达和功能 在神经元表型中可以重现人诱导多能干细胞（iPSC）中的内体功能障碍 衍生神经元来自散发性AD和DS的iPSC将分化成前脑神经元。表型 显示由Synj1介导的蛋白质将在包括内体在内的功能性人类神经元中重现 形态和功能，棘形态，脂质失调和与BIN1的功能复合物形成， 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，新的细胞靶点很可能将 从功能性iPSC衍生的神经元的相应脂质组学和RNAseq研究中出现。我们还将 开发适合未来治疗开发的关键人类神经元细胞模型。

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.