Molecular Determinants for In vivo Functional Reprogramming of Cortical Output Neurons and Circuits

项目总结/摘要 目前还没有成功的治疗方法可以恢复受损的大脑回路。神经元损失 神经退行性疾病或创伤导致神经和认知功能障碍，对神经系统造成巨大负担。 人体健康迫切需要找到神经回路修复的策略。直接重编程 这些方法对大脑修复有很大的希望。他们在功能电路恢复方面的成功将取决于他们的 将其他细胞转化为神经元的能力，其功能与电路中受损的神经元相匹配。 这种精确的转换已经在小鼠大脑皮层中观察到， 神经元，它可以获得连接属性，包括远程投影，典型的其他 离皮质亚型。虽然这是朝着电路修复迈出的有希望的一步， 当在胚胎或不成熟状态下诱导重编程时观察到。 在分化的神经元中阻止重编程的机制或保持神经元重编程的机制可能是神经元细胞凋亡的机制。 一生不变的身份是不被理解的。因此，我们的目标是研究关键机制， 在分化的神经元中维持神经元亚型身份，并确定它们如何限制重编程， 时间这将揭示阻碍体内神经元亚型之间功能转换的障碍。我们提出 为了研究这些机制，在离皮质神经元，特别是在体内重编程的背景下， 皮质丘脑神经元（CTn）产生脑下投射神经元（SCn），一种临床相关神经元 在肌萎缩侧索硬化症中退化的亚型，其轴突被脊髓损伤破坏。 在这个提议中，我们将研究身份维持机制是否可以在体内被操纵， 将CTn重编程为功能性SCn（目标1），我们将确定这些机制是否可以 在成熟CTn中失活，以消除阻止CTn转化为SCn的障碍（目标2），我们将 阐明阻止CTn在体内转化为SCn的潜在下游信号（目的3）。

PROJECT SUMMARY/ABSTRACT Currently there is no successful treatment that restores damaged brain circuitry. Neuron loss by either neurodegenerative diseases or trauma causes neurological and cognitive dysfunction, posing a great burden for human health. There is a critical need to find strategies for neural circuit repair. Direct reprogramming approaches hold great promise for brain repair. Their success in functional circuit restoration will depend on their capacity to convert other cells into neurons with functions matching those of the neurons damaged in a circuit. This precise conversion has been observed in the mouse cerebral cortex between cortical output (corticofugal) neurons, which can acquire the connectivity properties, including long-range projections, typical of other corticofugal subtypes. Though this is a promising step forward toward circuit repair, this precise conversion has been observed when reprogramming is induced at embryonic or immature states. The mechanisms that preclude reprogramming in differentiated neurons or the mechanisms that keep neuron identity unchanged throughout life are not understood. Hence, our goal is to investigate mechanisms critical for maintaining neuron subtype identity in differentiated neurons and determine how they limit reprogramming over time. This will reveal barriers that preclude functional conversion between neuron subtypes in vivo. We propose to investigate these mechanisms in corticofugal neurons, specifically in the context of in vivo reprogramming of Corticothalamic neurons (CTn) to produce Subcerebral projection neurons (SCn), a clinically relevant neuron subtype that degenerates in Amyotrophic lateral sclerosis and whose axons are damaged by spinal cord injury. In this proposal we will investigate whether identity maintenance mechanisms can be manipulated for in vivo reprogramming of CTn into functional SCn (Aim 1), we will determine whether these mechanisms can be inactivated in mature CTn to eliminate barriers that preclude CTn conversion into SCn (Aim 2), and we will elucidate the underlying downstream signals that preclude conversion of CTn into SCn in vivo (Aim 3).