Molecular Controls over Induction of Neurogenesis for Brain Repair

描述（由申请人提供）：所提出的实验的长期目标是修复新皮层投射神经元回路。这项工作的最终目标是通过操纵内源性神经祖细胞原位修复。这可能导致皮质及其输出电路（例如皮质脊髓）的退行性、发育性或获得性疾病的治疗。在新皮层中，这种未来疗法的有效性可能关键取决于内源性祖细胞是否可以被精确诱导形成正确的、亚型特异性的神经元;分化和适当整合;以及重新形成长距离投射和复杂的功能连接。在提交该资助的初始阶段时，我们最近发表了（Magavi，Nature，2000; Scharff，Neuron，2000）该领域的第一个神经发生诱导的演示，新神经元的诞生，来自成年大脑中的内源性祖细胞。我们选择皮质丘脑投射神经元（CThPN）及其发育用于小鼠神经发生诱导的集中研究，因为它们是长距离皮质投射神经元的原型群体，并且因为它们的位置最接近尾侧皮质SVZ祖细胞的可用池。我们假设（现在有大量的发育数据和试点成人数据），存在部分命运特异性的新皮质祖细胞，能够分化为离皮质神经元，包括CThPN（Molyneaux，Neuron，2005; Arlotta，Neuron，2005; Molyneaux，Nat Rev NSci，2007; Lai，Neuron，2008; Joshi，Neuron，2008; Azim，2008）。未来治疗操纵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。虽然我们已经取得了相当大的进展，确定细胞和分子条件，使皮质神经发生和成人皮质电路的部分修复，许多问题仍然有待研究。这些问题构成了拟议研究的基础。基于最近的结果，提出的实验（目的1）使用体内功能的丧失和获得来功能性地研究FOG-2，一种新鉴定的对CThPN发育至关重要的转录调节因子;（目的2）研究两种新的候选组合的对CThPN出生和发育的分子遗传控制;（目的3）研究最近在发育过程中鉴定的部分命运限制的神经祖细胞是否存在于成年小鼠新皮层中，具有潜在增强的产生离皮质神经元的能力;和（目的4）通过操纵对CThPN发育的关键分子遗传控制，从成年小鼠前脑中（潜在）部分命运限制的祖细胞诱导CThPN神经发生。总之，这些实验将显著提高我们诱导类型特异性神经发生的能力，并最终指导成年CNS的功能性回路修复。 公共卫生相关性：退行性和创伤性神经系统疾病是造成巨大个人痛苦和残疾的根源，给公共卫生造成巨大的财政和社会负担。神经祖细胞（有时称为“神经干细胞”）存在于成年大脑中，并且已经在小鼠中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。对连接大脑特定中心和大脑与脊髓之间的神经元的发育和存活的分子控制的了解，将为治疗涉及皮质“投射”神经元的神经变性疾病，如亨廷顿病（HD）提供新的方法;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）和遗传性痉挛性截瘫（HSP）;和创伤性脊髓损伤。基于最近的工作确定定义的祖细胞和分子控制脑神经元的出生和发育，该项目将研究机制，通过该机制，新的神经元的出生（神经发生）可以诱导小鼠从（特定）祖细胞已经在成年大脑中，朝着治疗策略的设计，以修复，调节，或保存受损或退化的神经元在大脑中。

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.