Molecular Controls over Induction of Neurogenesis for Brain Repair

描述(申请人提供)：拟议实验的长期目标是修复新皮质投射神经元电路。这项工作旨在通过操纵内源性神经前体细胞原位修复的最终目标。这可能导致治疗皮质及其输出回路(如皮质脊髓)的退行性、发育性或获得性疾病。在新皮质，这种未来疗法的有效性可能关键取决于能否准确地诱导内源性前体细胞形成正确的、亚型特定的神经元；适当地分化和整合；以及重新形成远距离投射和复杂的功能连接。在提交这项资助的初始阶段时，我们最近已经发表了(Magavi，Nature，2000；Scharff，Neuron，2000)该领域的第一个关于从成人大脑的内源性祖细胞诱导神经发生，即新神经元的诞生的演示。我们选择皮质丘脑投射神经元(CThPN)及其发育作为小鼠的重点研究对象，以诱导神经发生，因为它们是长距离皮质投射神经元的典型群体，而且它们的位置最接近尾侧皮质SVZ祖细胞的可用池。我们假设(现在有大量的发育中的数据和初步的成人数据)存在部分命运指定的新皮质前体细胞，有能力分化为皮质分离神经元，包括CThPN(Molyneaux，Neuron，2005；Arlotta，Neuron，2005；Molyneaux，NAT Rev NSCI，2007；Lai，Neuron，2008；Joshi，Neuron，2008；Azim，2008)。未来治疗内源性祖细胞和诱导神经发生的下一个合乎逻辑的步骤将是通过操纵组合分子遗传控制来定向分化特定的神经元群体。尽管我们已经取得了相当大的进展，确定了细胞和分子条件，使皮质神经发生和成人皮质回路的部分修复，仍有许多问题有待研究。这些问题构成了拟议研究的基础。以最近的结果为基础，拟议的实验(目的1)利用体内的功能丧失和获得对CThPN发育至关重要的新发现的转录调控因子FOG-2进行功能研究；(目的2)研究控制CThPN出生和发育的两种新的候选分子遗传组合；(目的3)研究最近在发育过程中被发现的部分命运受限的神经前体细胞是否存在于成年小鼠新皮质中，并且可能增强其产生皮质分离神经元的能力；以及(目的4)通过操纵对CThPN发育进行关键的分子遗传控制来诱导成年小鼠前脑(潜在的)命运受限的祖细胞诱导CThPN神经发生。总之，这些实验将显著提高我们诱导特定类型的神经发生并最终直接修复成人中枢神经系统功能回路的能力。 公共卫生相关性：退行性和创伤性神经疾病是巨大的个人痛苦和残疾的根源，它们造成了巨大的公共卫生财政和社会负担。神经前体细胞(有时被称为神经干细胞)存在于成人大脑中，并在小鼠身上被发现能够在特殊条件下产生少量新的大脑皮层神经细胞(神经元)。一些成年祖细胞可能已经部分决定产生与人类疾病有关的神经元类型。了解连接大脑特定中心和脑与脊髓之间的神经元的发育和存活的分子控制知识，将为治疗涉及皮质“投射”神经元的神经退行性疾病提供新的方法，如亨廷顿病(HD)；皮质脊髓运动神经元退行性疾病如ALS、原发性侧索硬化症(PLS)和遗传性痉挛截瘫(HSP)；以及创伤性脊髓损伤。该项目将在最近确定已确定的前体细胞和对脑神经元出生和发育的分子控制的基础上，研究从成年大脑中已有的(特定)前体细胞诱导小鼠产生新神经元(神经发生)的机制，以设计治疗策略来修复、调节或保存大脑中受损或退化的神经元。

DESCRIPTION (provided by applicant): The long-term goal of the proposed experiments is repair of neocortical projection neuron circuitry. This work aims toward the ultimate goal of repair by manipulation of endogenous neural progenitors in situ. This could lead to therapies for degenerative, developmental, or acquired diseases of cortex and its output circuitry (e.g. corticospinal). In neocortex, the effectiveness of such future therapies could depend critically on whether endogenous progenitors can be precisely induced to form the correct, subtype-specific neurons; differentiate and integrate appropriately; and re-form long-distance projections and complex functional connections. At the time of submission for the initial period of this grant, we had recently published (Magavi, Nature, 2000; Scharff, Neuron, 2000) the field's first demonstrations of induction of neurogenesis, the birth of new neurons, from endogenous progenitors in the adult brain. We chose corticothalamic projection neurons (CThPN) and their development for focused study in mice toward induction of neurogenesis because they are a prototypical population of long-distance cortical projection neurons, and because of their location closest to the available pool of caudal cortical SVZ progenitors. We hypothesized (now with substantial data during development and pilot adult data) that there exist partially fate-specified neocortical progenitors competent to differentiate into corticofugal neurons, including CThPN (Molyneaux, Neuron, 2005; Arlotta, Neuron, 2005; Molyneaux, Nat Rev NSci, 2007; Lai, Neuron, 2008; Joshi, Neuron, 2008; Azim, 2008). A next logical step toward future therapeutic manipulation of endogenous progenitors and induction of neurogenesis will be directed differentiation of specific neuron populations by manipulating combinatorial molecular-genetic controls. Though we have made considerable progress identifying cellular and molecular conditions that enable cortical neurogenesis and partial repair of adult cortical circuitry, many questions still remain to be investigated. These questions form the basis of the proposed research. Building on recent results, proposed experiments (Aim 1) functionally investigate FOG-2, a newly identified transcriptional regulator critical for CThPN development, using loss- and gain-of-function in vivo; (Aim 2) investigate two new candidate combinatorial molecular-genetic controls over CThPN birth and development; (Aim 3) investigate whether partially fate- restricted neural progenitors, recently identified during development, exist in the adult mouse neocortex, with potentially enhanced competence to generate corticofugal neurons; and (Aim 4) induce CThPN neurogenesis from (potentially) partially fate-restricted progenitors in the adult mouse forebrain via manipulation of critical molecular-genetic controls over CThPN development. Together, these experiments will significantly advance our ability to induce type-specific neurogenesis and ultimately direct functional circuit repair of the adult CNS. PUBLIC HEALTH RELEVANCE: Degenerative and traumatic neurological disorders are the source of great personal suffering and disability, and they account for a huge public health financial and social burden. Neural progenitors (sometimes termed "neural stem cells") exist in the adult brain, and have been found in mice to be capable of generating a small number of new cerebral cortex nerve cells (neurons) under special conditions. Some adult progenitors might already be partially decided to generate types of neurons involved in human diseases. Knowledge of the molecular controls over the development and survival of the neurons that connect between specific centers of the brain, and the brain to the spinal cord, will provide new approaches for the treatment of neurodegenerative diseases involving cortical "projection" neurons, such as Huntington's disease (HD); corticospinal motor neuron degenerative diseases such as ALS, primary lateral sclerosis (PLS), and hereditary spastic paraplegia (HSP); and traumatic spinal cord injury. Building on recent work identifying defined progenitors and molecular controls over brain neuron birth and development, this project will investigate mechanisms by which the birth of new neurons (neurogenesis) can be induced in mice from (specific) progenitors already in the adult brain, toward design of therapeutic strategies to repair, modulate, or preserve injured or degenerating neurons in the brain.