Molecular Mechanisms of CTIP2 Function in Corticospinal Motor Neuron Development

7.项目摘要/摘要 拟议中的实验的长期目标都是为了阐明分子遗传控制对 皮质脊髓运动神经元(CSMN)(及相关的新皮质)的神经元亚型特异性发育 投射神经元)，并潜在地使未来修复退化或损伤的CSMN的方法成为可能。 CSMN既是所有新皮质投射神经元发育的原型，也是临床上重要的 肌萎缩侧索硬化症/运动神经元病(ALS/MND)和 其轴突损伤是脊髓损伤中运动功能丧失的核心。拟议中的实验将深入 研究中枢重要的CSMN/亚脑特异性转录因子CTIP2(COUP-Tf)的功能 相互作用蛋白2)及其类似物CTIP1在小鼠新皮质CSMN及相关神经元发育中的作用。 Ctip2越来越多地成为CSMN发展和连接的关键调节因素，以及 作为多投射神经元亚型分化调节(主要是抑制)的共同靶点 小路。从其他器官系统中已知Ctip2参与了发育谱系的指定 决定。在新皮质内，CTIP2由CSMN和相关的脑下投射特异性表达 神经元，是CSMN轴突生长、丛生和靶向所必需的。而Ctip2则拥有 作为CSMN发展的核心，其功能的大部分方面仍不清楚。 大量的初步数据支持这些目标。该实验室以前的工作确定Ctip2是一种 关键的CSMN分子控制，并证明Ctip2-/-小鼠的CSMN轴突以前被错误地发送 穿透内囊(IC)，在IC内脱叉，不能投射到脊髓(SC)。 因为CTIP2还控制着纹状体中型棘神经元(MSN)的分化，MSN围绕着 假设Ctip2-/-CSMN与SC的连接存在缺陷。 可能是由于Ctip2-/-MSN中轴突生长和导向控制的失调所致。仅缺少Ctip2的小鼠 在新皮质(Emx1-Cre；Ctip2fl/fl)中发现CSMN的一个子集进入并在IC内成束，甚至有些甚至 联系SC。其他的初步研究发现，Ctip2与Ctip2之间存在交叉抑制作用 以控制深层投射神经元的发育，而Ctip1还调节区域组织。 拟议的实验将：(目标1、2)划定CSMN自主和非CSMN自主角色 Ctip2在CSMN轴突生长和束形成中的作用；(AIMS 3，4)调查一个新发现的遗传交叉 Ctip2及其同源基因Ctip1在CSMN发育中的抑制性相互作用及其独立作用 Ctip1在其他深层投射神经元的区域组织和发育中的表达。超越现实的实验 这一建议可以识别CSMN中受Ctip2直接或间接调控的基因。这些研究将阐明 CSMN分化的中央调节因子Ctip2单独以及与其他基因共同作用的机制 指导这种发育原型、临床上重要的神经元类型的发展的精确度。

7. PROJECT SUMMARY / ABSTRACT The long-term goals of the proposed experiments are both to elucidate molecular-genetic controls over the neuron subtype-specific development of corticospinal motor neurons (CSMN) (and related neocortical projection neurons), and to potentially enable future approaches to repair of degenerating or injured CSMN. CSMN are both developmentally prototypical for all neocortical projection neurons, and clinically important as the brain neurons that degenerate in amyotrophic lateral sclerosis / motor neuron disease (ALS/MND) and whose axonal injury is central to loss of motor function in spinal cord injury. Proposed experiments will deeply investigate function of the centrally important CSMN/subcerebral-specific transcription factor CTIP2 (COUP-TF interacting protein 2) and its paralog CTIP1 in development of CSMN and related neurons in murine neocortex. Ctip2 has increasingly emerged as both a critical regulator of development and connectivity of CSMN, and as a common target for regulation (largely repression) by multiple projection neuron subtype differentiation pathways. Ctip2 is known from other organ systems to be involved in developmental lineage specification decisions. Within the neocortex, CTIP2 is specifically expressed by CSMN and related subcerebral projection neurons, and is necessary for outgrowth, fasciculation, and targeting of CSMN axons. While Ctip2 has emerged as centrally important for CSMN development, most aspects of its function remain unknown. Substantial preliminary data support these aims. Previous work from this laboratory identified Ctip2 as a critical CSMN molecular control, and demonstrated that CSMN axons in Ctip2-/- mice are misrouted before penetrating the internal capsule (IC), defasciculate in the IC, and fail to project to the spinal cord (SC). Because CTIP2 also controls differentiation of striatal medium-sized spiny neurons (MSN), which surround CSMN axons in the IC, the hypothesis is suggested that some defects in Ctip2-/- CSMN connectivity to SC might result from dysregulation of axon growth and guidance controls in Ctip2-/- MSN. Mice lacking Ctip2 only in neocortex (Emx1-Cre;Ctip2fl/fl) reveal that a subset of CSMN enter and fasciculate in the IC, and some even reach the SC. Other preliminary studies find that the Ctip2 paralog Ctip1 interacts cross-repressively with Ctip2 to control deep-layer projection neuron development, and that Ctip1 additionally regulates areal organization. Proposed experiments will: (Aims 1, 2) delineate CSMN-autonomous and non-CSMN-autonomous roles of Ctip2 in CSMN axon growth and fasciculation; (Aims 3, 4) investigate a newly-identified genetically cross- repressive interaction between Ctip2 and its paralog Ctip1 in CSMN development, as well as independent roles of Ctip1 in areal organization and development of other deep-layer projection neurons. Experiments beyond this proposal could identify genes regulated directly or indirectly by Ctip2 in CSMN. These studies will elucidate mechanisms by which Ctip2, a central regulator of CSMN differentiation, acts alone and with other genes to instruct the precision of development of this developmentally prototypical, clinically important neuron type.