Astrocyte-secreted proteins as modulators of neurodegeneration in Down Syndrome and Alzheimers Disease

项目摘要/摘要 唐氏综合征(DS)是一种由21号染色体三体引起的神经发育障碍，随着年龄的增长 大多数DS患者会出现与阿尔茨海默病(AD)相关的神经病理特征，包括 淀粉样斑块沉积和星形胶质细胞增生症以及临床痴呆(DS与AD并存为DS-AD)。 淀粉样前体蛋白(APP)突变与AD有关，DS患者APP基因三倍体， 这表明这是重叠病理的一个促成因素。研究表明，星形胶质细胞 DS和AD疾病进展的调节因子。星形胶质细胞通过释放 分泌的蛋白质，最近的工作表明，星形胶质细胞的蛋白质分泌在DS和AD中都是失调的。 Allen实验室在Ts65Dn DS小鼠模型中发现了&gt；700星形胶质细胞分泌的蛋白质表达异常。 新生儿时间点。有趣的是，促生长蛋白(PTN)的分泌被下调了4倍。 来自Ts65Dn星形胶质细胞，随后对PTN基因敲除小鼠的研究表明，它们具有表型复制 Ts65Dn小鼠在多个方面的表现，包括树突长度和脊柱密度的减少。单核RNA- 测序研究表明阿尔茨海默病“疾病相关”星形胶质细胞亚群下调转录 编码许多促突触生成因子，包括PTN。这一提议的主要假设是：1) 在DS-AD和AD中，重叠的星形胶质细胞分泌蛋白网络改变，2)PTN分泌减少 星形胶质细胞的释放促进了DS-AD和AD的疾病进展。这项建议采取了不偏不倚的方法。 为了研究DS-AD和AD小鼠模型中星形胶质细胞分泌组的变化，以及靶向 探讨PTN挽救神经病理表型的可能性。AIM 1/K99利用生物素- 介导性邻近标记(一种内质网定位的TurboID病毒)为 疾病早、中、晚期DS-AD和AD模型小鼠体内星形胶质细胞特异性分泌体。 这一目标为研究人员提供了广泛的质谱学技术和定量培训 蛋白质组学分析。AIM 2/R00利用病毒介导的PTN在星形胶质细胞中过表达来研究PTN是否 可挽救DS-AD和AD模型小鼠的脊柱密度、星形胶质细胞增多症和空间记忆障碍。 此外，研究人员将利用来自目标1的星形胶质细胞特定分泌组数据集来研究其他 未来实验室中的蛋白质候选者。指导团队由星形细胞领域的领军人物尼古拉·艾伦博士组成 生物学；Alan Saghatelian博士，他将提供定量蛋白质组学方面的专业知识；Jolene Diedrich博士，麻省理工学院 光谱核心主任；行为核心主任尼克·安德鲁斯博士；神经学家道格拉斯·加拉斯科博士 他是阿尔茨海默病研究中心(ADRC)的副主任 加州大学圣地亚哥分校(UCSD)。这项工作将在世界级的索尔克生物研究所进行 在ADRC和UCSD研究并建立网络联系，为博士提供必要的基础。 布兰德布拉的独立研究生涯专注于神经退行性变中星形胶质细胞分泌的蛋白质。

Project Summary/Abstract Down Syndrome (DS) is a neurodevelopmental disorder caused by trisomy of chromosome 21, and with age a majority of DS patients develop neuropathological hallmarks associated with Alzheimer’s Disease (AD), including amyloid plaque deposition and astrogliosis, as well as clinical dementia (cooccurrence of DS with AD is DS-AD). Amyloid precursor protein (APP) mutations are linked to AD, and DS patients have triplication of the APP gene, suggesting this as a contributing factor to the overlapping pathology. Research suggests astrocytes are regulators of both DS and AD disease progression. Astrocytes modulate synapses through the release of secreted proteins, and recent work suggests that astrocyte protein secretion is dysregulated in both DS and AD. The Allen lab identified >700 astrocyte-secreted proteins dysregulated in the Ts65Dn mouse model of DS at neonatal timepoints. Of interest, secretion of the pro-growth protein pleiotrophin (Ptn) was >4x down-regulated from Ts65Dn astrocytes, and subsequent investigations of Ptn knockout mice revealed that they phenocopy Ts65Dn mice in many aspects, including decreased dendrite length and spine density. Single nucleus RNA- Sequencing studies show that subsets of “disease-associated” astrocytes in AD down-regulate transcripts encoding for many pro-synaptogenic factors, including Ptn. The main hypotheses of this proposal are that: 1) a network of overlapping astrocyte-secreted proteins is altered in DS-AD and AD, and 2) decreased Ptn secretion from astrocytes contributes to disease progression in DS-AD and AD. This proposal takes an unbiased approach to characterize changes in the astrocyte secretome in DS-AD and AD mouse models, as well as a targeted approach to investigate the potential for Ptn to rescue neuropathological phenotypes. Aim 1/K99 utilizes biotin- mediated proximity labeling (an endoplasmic reticulum localized TurboID virus) to create novel datasets for the in vivo astrocyte-specific secretome in DS-AD and AD mouse models at early, middle and late stages of disease. This aim provides the investigator with extensive training in mass spectrometry technology and quantitative proteomics analysis. Aim 2/R00 employs viral-mediated Ptn overexpression in astrocytes to investigate if Ptn can rescue spine density, astrogliosis and spatial memory impairments in DS-AD and AD mouse models. Additionally, the investigator will utilize the astrocyte-specific secretome datasets from Aim 1 to investigate other protein candidates in their future laboratory. The mentoring team consists of Dr. Nicola Allen, a leader in astrocyte biology; Dr. Alan Saghatelian, who will provide expertise in quantitative proteomics; Dr. Jolene Diedrich, mass spectrometry core director; Dr. Nick Andrews, behavioral core director; and Dr. Douglas Galasko, a neurologist specializing in dementia and Associate Director of the Alzheimer’s Disease Research Center (ADRC) at the University of California San Diego (UCSD). The work will take place at the world class Salk Institute for Biological Studies and establish networking connections at the ADRC and UCSD, providing an essential foundation for Dr. Brandebura’s independent research career focused on astrocyte-secreted proteins in neurodegeneration.