Exploring the Pathogenic Mechanisms of Batten's disease MFSD8 mutations using patient iPSC derived neurons.

MFSD 8基因突变导致CLN 7巴滕氏病（BD），这是一种罕见的神经退行性溶酶体储存障碍，其特征在于称为蜡样物质的脂色素在大脑中的积累。此外，MFSD 8突变最近与额颞叶痴呆（FTD）相关，其他BD相关基因与帕金森病（ATP 13 A2）和其他FTD亚型（GRN，CTSD）相关。CLN 7 BD福尔斯属于称为神经元蜡样脂褐质病（NCL）的更广泛的儿科疾病类别，其具有神经元中蜡样物质积聚的共同组织病理学和神经系统症状，包括痴呆、失明、癫痫发作和过早死亡。MFSD 8基因编码CLN 7蛋白，CLN 7蛋白是一种定位于溶酶体的功能未知的膜蛋白。导致CLN 7 BD的突变是功能丧失，并且许多已知的突变导致过早停止或使蛋白质不稳定的点突变。我们先前在患者成纤维细胞中的研究表明，CLN 7的缺失降低了溶酶体水解酶活性、自噬通量和自体荧光物质的积累。虽然这些研究有助于我们了解CLN 7如何导致疾病，但导致神经退行性变的机制尚不清楚。此外，还没有在相关的患者源性神经元模型中进行研究。在这里，我们建议使用来自不同BD患者的几个iPSC系来探索CLN 7突变引起的神经毒性的机制。我们的初步数据表明，CLN 7 BD系可以在体外发育成皮质神经元，但表现出溶酶体表型和减少的神经突延伸。在目标1中，我们计划使用这个已建立的神经元模型来确定CLN 7的丢失如何影响蛋白质组的稳定性和蛋白质溶解度，以发现新的途径并产生关于CLN 7 BD中细胞死亡如何发生的假设。在目标2中，我们将评估旨在恢复CLN 7神经元中蛋白质稳态的救援机制，以及将野生型星形胶质细胞与CLN 7-BD神经元共培养以评估神经胶质细胞在痴呆中的作用。由于几乎没有关于CLN 7如何引起神经功能障碍的机制信息，我们的研究有可能发现CLN 7 BD和其他具有相似病理学的NCL的新治疗途径。除NCL外，MFSD 8突变与FTD（一种年龄相关的神经退行性疾病）相关，因此我们的研究可能与更常见的年龄相关的神经退行性疾病相关。由于有越来越多的证据表明溶酶体功能障碍常见的散发性疾病，包括帕金森氏病和其他突触核蛋白病，我们的研究可能会对该领域产生广泛的影响。

Mutations in the MFSD8 gene cause CLN7 Batten’s disease (BD), a rare neurodegenerative lysosomal storage disorder characterized by the accumulation of a lipopigment called ceroid in the brain. Furthermore, MFSD8 mutations were recently associated with frontotemporal dementia (FTD), and other BD-associated genes are linked to Parkinson’s disease (ATP13A2) and other subtypes of FTD (GRN, CTSD). CLN7 BD falls within a broader category of pediatric diseases called neuronal ceroid lipofuscinoses (NCL) that share common histopathology of ceroid accumulation in neurons and neurological symptoms including dementia, blindness, seizures, and premature death. The MFSD8 gene encodes the CLN7 protein, a membrane protein of unknown function that is localized to lysosomes. Mutations that cause CLN7 BD are loss of function and many of the known mutations result in premature stops or point mutations that destabilize the protein. Our previous studies in patient fibroblasts demonstrated that loss of CLN7 reduces lysosomal hydrolase activity, autophagic flux, and the accumulation of autofluorescent material. While these studies contributed to our understanding of how CLN7 leads to disease, the mechanisms that lead to neurodegeneration are not known. Furthermore, there are no studies done in relevant patient-derived neuronal models. Here, we propose to explore the mechanisms of neurotoxicity caused by CLN7 mutations, using a several iPSC-lines derived from distinct BD patients. Our preliminary data indicates that CLN7 BD lines can develop into cortical neurons in vitro, but demonstrate lysosomal phenotypes and reduced neurite extensions. In aim 1, we plan to use this established neuronal model to determine how loss of CLN7 influences the stability of the proteome and protein solubility to discover novel pathways and generate hypotheses for how cell death occurs in CLN7 BD. In aim 2, we will assess rescue mechanisms that aim to restore protein homeostasis in CLN7 neurons, as well as co-culturing wild-type astrocytes with CLN7-BD neurons to assess the role of glia cells in dementia. Since almost no mechanistic information is known about how CLN7 causes neurological dysfunction, our studies have the potential to uncover novel therapeutic pathways for CLN7 BD and other NCLs that share similar pathologies. Beyond NCLs, mutations in MFSD8 are associated with FTD, an age-related neurodegenerative disorder, and therefore our studies may be relevant to more common age-related neurodegeneration. Since there is accumulating evidence for lysosomal dysfunction common sporadic diseases including Parkinson’s disease and other synucleinopathies, our studies may have a broad impact on the field.