NPTX2: Preserving memory circuits in normative aging and Alzheimer's Disease

摘要 衰老对人类大脑的影响表现出广泛的个体差异，从早发性阿尔茨海默氏症 疾病（AD）到维持认知清晰度进入第10个十年。挑战在于理解为什么 衰老可以产生如此不同的结果，以及为什么它对神经退行性疾病的风险有如此深刻的贡献。 疾病我们已经从记忆的分子途径的角度研究了衰老和AD 巩固并确定一个名为NPTX 2的基因为人类认知提供了重要线索， 失败NPTX 2由锥体神经元表达，并在其兴奋性突触分泌到小清蛋白上 中间神经元（PV）控制抑制回路功能。NPTX 2和PV功能标志物是显著的 NPTX 2在患有AD的人脑中下调，并且CSF水平与两种疾病状态相关 和认知能力。NPTX 2在维持认知功能的个体的大脑中没有下调。 尽管淀粉样蛋白积聚（无症状AD），但仍清晰。这些和其他发现支持了这样一种假设， NPTX 2与对认知至关重要的大脑弹性相关，并在从健康到不健康的转变中失败 衰老目的1将确定与NPTX 2表达保留或恶化相关的信号通路 从具有特殊认知能力的老年人到AD患者。研究使用 靶向蛋白质组学方法与批量和单核RNA测序相结合，并将专门检查 假设NPTX 2功能丧失与中间神经元细胞特性的变化有关。目的2 扩展了目标1的目标，以建立使用等基因的NPTX 2下调的细胞机制。 编码APP和PS1家族性突变的人iPS神经元。具有fAD突变的iPS神经元显示， NPTX 2表达的显著和特异性降低，并提供了分离和 验证关键疾病途径。分析将包括TMT差示质谱和RNAseq。 候选途径将使用CRISPR和药理学方法进行操作和测试。目标3 将提供第一个测试的假设，即NPTX 2功能丧失（LOF）在成人大脑是因果关系， 在AD发病机制的背景下，回路功能障碍和认知下降。实验使用一种新的 在转基因APP/PS1 AD模型中建立NPTX 2条件性缺失的大鼠遗传模型（Tg 344- AD）。分析将包括海马子区域CA 1和CA 2中的高密度电生理记录。 CA 3以及AD标志物的行为测试和组织病理学评估。单核RNAseq 在CA 3中进行的标记将在淀粉样蛋白病理学的背景下定义NPTX 2 LOF的特征。这些数据将 与目标1和2的结果交叉引用，作为原因的综合种属间分析的一部分 以及NPTX 2 LOF的后果。综合研究将加深我们对机制的理解， 赋予认知健康或使大脑偏向疾病。

Abstract The effect of aging on the human brain shows wide individual variation ranging from early onset Alzheimer's disease (AD) to maintenance of cognitive clarity into the 10th decade. The challenge is to understand why aging can have such disparate outcomes, and why it contributes so profoundly to the risk of neurodegenerative disease. We have examined aging and AD from the perspective of molecular pathways that underlie memory consolidation and determined that a gene termed NPTX2 provides an important clue to human cognitive failure. NPTX2 is expressed by pyramidal neurons and secreted at their excitatory synapses on parvalbumin interneurons (PV) to control inhibitory circuit function. NPTX2 and markers of PV function are prominently down-regulated in the brain of humans with AD, and CSF levels of NPTX2 correlate with both disease state and cognitive performance. NPTX2 is not down-regulated in the brains of individuals who maintain cognitive clarity despite amyloid accumulation (asymptomatic AD). These and other findings support the hypothesis that NPTX2 is associated with brain resilience critical for cognition and fails in the shift from healthy to unhealthy aging. Aim 1 will identify signaling pathways associated with preserved or deteriorated NPTX2 expression across the spectrum from older individuals with exceptional cognition to those with AD. Studies use an approach of targeted proteomics combined with bulk and single nuclei RNAseq, and will specifically examine the hypothesis that NPTX2 loss-of-function is associated with changes in interneuron cell properties. Aim 2 extends the goals of Aim 1 to establish the cellular mechanism of NPTX2 down-regulation using isogenic human iPS neurons encoding familial mutations of APP and PS1. iPS neurons with fAD mutations show profound and specific reductions of NPTX2 expression and provide an extraordinary opportunity to isolate and validate critical disease pathways. Analyses will include TMT differential mass spectroscopy and RNAseq. Candidate pathways will be manipulated and tested using CRISPR and pharmacological approaches. Aim 3 will provide the first test of the hypothesis that NPTX2 loss of function (LOF) in the adult brain is causal for circuit dysfunction and cognitive decline in the context of AD pathogenesis. Experiments use a newly established rat genetic model for conditional deletion of NPTX2 in a transgenic APP/PS1 AD model (Tg344- AD). Analyses will include high density electrophysiological recordings in hippocampal subregions CA1 and CA3 together with behavior tests and histopathological assessments of AD markers. Single nuclei RNAseq performed in CA3 will define the signature of NPTX2 LOF in the context of amyloid pathology. These data will be cross-referenced with findings from Aims 1 and 2 as part of an integrated interspecies analysis of the cause and consequences of NPTX2 LOF. Combined studies will deepen our understanding mechanisms that can confer cognitive health or bias the brain towards disease.