Animal models to study iron homeostasis

描述(申请人提供)：铁在几种神经退行性疾病，如阿尔茨海默病(AD)和帕金森病(PD)中经历变性的大脑区域积累(1-3)。然而，铁在神经退化过程中的确切作用尚不清楚。该项目的长期目标是确定和描述铁管理不善可能导致神经退化的机制(S)。我们之前已经描述了一种神经退行性疾病，我们将其命名为遗传性铁素病(HF)，它是由铁蛋白轻多肽(FTL)基因突变引起的。心衰是一种严重的运动障碍，其神经病理学特征是铁和铁蛋白在整个中枢神经系统内异常积聚(4)。我们认为，导致心力衰竭发生的两个关键的毒性病理机制是：1)铁蛋白毒性功能的增强；2)铁蛋白正常功能的丧失。一个关键的问题是，这些机制是单独作用还是共同作用导致心衰。在目前的应用中，我们将开发两种新的条件细胞特异性铁蛋白敲除，这将使我们能够确定铁蛋白功能的丧失是仅仅与疾病过程有关，还是与疾病的病因有关。通过使用特定的启动子，这些模型将使我们能够在不影响其他器官系统铁代谢的情况下，研究中枢神经系统中离散细胞群中铁蛋白(Fth1基因)铁氧合酶活性丧失和/或铁蛋白(FTL基因)铁储存功能丧失的后果。目前，还没有体内模型来研究铁蛋白功能丧失的后果。在这项应用中开发的动物模型将解决这一问题，将允许检查中枢神经系统细胞中的铁蛋白故障，并将绕过已知的Fth1基因敲除小鼠的胚胎致死(5，6)。为了验证我们的假设，我们的具体目标是：特定目标1：有条件地敲除(CKO)小鼠中枢神经系统离散细胞群体中的Fth1和FTL基因，以确定受影响细胞中的铁代谢失调是否与这些CKO小鼠神经退化的原因有关，铁蛋白的功能丧失将以神经元或胶质细胞为靶点，这两类细胞在HF中退化，使用表达CreERT2蛋白的特定启动子。重要的是，在特定启动子的控制下，使用我们的铁蛋白小鼠与表达CreERT2蛋白的转基因小鼠相结合，可以在其他细胞群或器官系统中实现铁蛋白功能的丧失。与公共卫生相关：铁代谢异常被认为是几种神经退行性疾病的发病原因，如阿尔茨海默病和帕金森病。我们建议开发新的小鼠模型，以便在体内详细分析正常衰老、异常脑铁代谢和神经退化之间的相互作用。重要的是，这些新的动物模型也可能对 铁代谢学研究铁在不同器官系统中的代谢以及与各种铁相关疾病有关的研究

DESCRIPTION (provided by applicant): Iron accumulates in brain regions that undergo degeneration in several neurodegenerative diseases such as Alzheimer disease (AD) and Parkinson disease (PD) (1-3). However, the precise role of iron in the neurodegenerative process is unclear. The long term goals of this project are to identify and characterize the mechanism(s) by which iron mismanagement may be involved in neurodegeneration. We have previously described a neurodegenerative disease that we named hereditary ferritinopathy (HF) which is caused by mutations in the ferritin light polypeptide (FTL) gene. HF is a severe movement disorder neuropathologically characterized by abnormal accumulation of iron and ferritin throughout the CNS (4). We propose that the two key toxic pathologic mechanisms implicated in the development of HF are i) a gain of a toxic function of ferritin and ii) a loss of the normal function of ferritin. A key question is whether these mechanisms are acting independently or together to lead to HF. In the present application, we will develop two novel conditional cell-specific ferritin knockouts that will allow us to determine whether a loss of function of ferritin is merely associated with the disease process or a causative agent in the disease. By using specific promoters, these models will allow us to study the consequences of a loss of the ferroxidase activity of ferritin (Fth1 gene) and/or the loss of the iron storage function of ferritin (Ftl gene) in discrete cell populations in the CNS without affecting iron metabolism in other organ systems. Currently, there are no in vivo models in which to study the consequences of a loss of function of ferritin. The animal models developed in this application will solve this problem, will allow the examination of ferritin malfunction in cells of the CNS, and will circumvent the embryonic lethality known to occur in Fth1 knock-out mice (5,6). In order to test our hypothesis, our specific aims are: Specific Aim 1: To conditionally knock-out (cKO) the murine Fth1 and the Ftl genes in discrete cell populations of the CNS to determine whether misregulation of iron metabolism in affected cells is implicated as a cause of neurodegeneration In these cKO mice, loss of function of ferritin will be targeted to neurons or glia, the two population of cells that degenerate in HF, using specific promoters expressing the CreERT2 protein. Importantly, ferritin loss of function could be achieve in other cell populations or organ systems using our "floxed" ferritin mice in combination with transgenic mice expressing the CreERT2 protein under the control of specific promoters. PUBLIC HEALTH RELEVANCE: Abnormal iron metabolism has been suggested to contribute to the development of several neurodegenerative diseases, like Alzheimer disease and Parkinson disease. We propose to develop new mouse models that will allow a detail in vivo analysis of the interaction of normal aging, abnormal brain iron metabolism and neurodegeneration. Importantly, these new animal models may be also useful for the study of iron metabolism in different organ systems and in association with a variety of iron-related diseases.