Molecular Controls over Induction of Neurogenesis for Brain Repair

描述（由申请人提供）：拟议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原位操纵内源性神经祖细胞进行修复。这可能导致治疗退行性、发展性或获得性疾病的皮质及其输出电路（如皮质脊髓）。在新皮层中，这种未来疗法的有效性可能主要取决于内源性祖细胞能否被精确诱导形成正确的、亚型特异性的神经元；适当地微分和积分；重新形成远距离投影和复杂的功能连接。在申请这项资助的初始阶段，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，来自成人大脑的内源性祖细胞。我们选择皮质丘脑投射神经元（CThPN）及其发育在小鼠中进行神经发生诱导的重点研究，因为它们是远距离皮层投射神经元的典型群体，并且因为它们的位置最接近可用的尾侧皮层SVZ祖细胞池。我们假设（现在有大量发育数据和实验性成人数据）存在部分命运指定的新皮层祖细胞，能够分化为皮质神经元，包括CThPN （Molyneaux, Neuron, 2005; Arlotta, Neuron, 2005; Molyneaux, Nat Rev NSci, 2007; Lai, Neuron, 2008; Joshi, Neuron, 2008; Azim, 2008）。未来治疗性操作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指导特定神经元群体的分化。尽管我们在确定皮层神经发生和成人皮层回路部分修复的细胞和分子条件方面取得了相当大的进展，但仍有许多问题有待研究。这些问题构成了拟议研究的基础。基于最近的结果，拟议的实验（Aim 1）利用体内功能丧失和获得，从功能上研究fog2，这是一种新发现的对CThPN发育至关重要的转录调节因子；（目的2）研究CThPN产生和发育的两个新的候选组合分子遗传调控；（目的3）研究最近在发育过程中发现的部分受命运限制的神经祖细胞是否存在于成年小鼠的新皮层中，并可能增强其产生皮质神经元的能力；（Aim 4）通过操纵CThPN发育的关键分子遗传控制，诱导成年小鼠前脑（可能）部分命运受限的祖细胞发生CThPN神经。总之，这些实验将显著提高我们诱导特定类型神经发生的能力，并最终指导成人中枢神经系统的功能电路修复。

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.