Strategies to maximize the functional benefit of regenerated corticospinal tract axons

项目总结 再生神经科学的一个主要努力是改善中枢神经损伤后轴突的生长。 系统(CNS)。然而，一旦实现增长，改善功能的第二个障碍是再生 轴突必须成功地与适当的突触后神经元形成突触接触。挑战 在损伤皮质脊髓束(CST)的脊髓损伤后，恢复有效回路的作用尤其严重。 对精细运动控制至关重要的通路。CST通过突触特异体介导下行运动控制 脊髓神经元的亚群，在人类和啮齿动物中同样包括一组不同的中间神经元 到灵长类动物特有的CST-运动神经元直接接触。这一领域取得了越来越大的成功 在促进CST轴突生长方面，行为恢复方面的成果一直滞后。这项工作将解决这一需求 监测再生的CST轴突的连通性，并优化其行为输出。要做到这一点，我们将 采用脊髓损伤的啮齿动物模型，并利用干细胞桥和病毒表达的联合 促再生基因KLF6，我们最近发现它能激发强劲的再生CST生长。在……里面 此外，我们将利用最近开发的跨突触病毒标记技术，使 前所未有的可视化突触后目标选择的能力。首先，我们将呈现KLF6表达式 可控性和可逆性，以便在再生发生后使KLF6静音，以确定是否 KLF6的长时间表达本身就会干扰行为恢复。这将解决紧迫的问题，即 促再生生长机制可能在多大程度上以牺牲有效突触为代价 精细化或目标选择。接下来，我们将通过以下方式来测试康复训练对雕刻目标选择的能力 再生CST并改善它们的行为输出。最后，我们将同时使用电气和化学发生技术 慢性提高再生CST轴突活性的手段，我们假设这两者都将增强CST 萌芽并提高对突触领土的竞争。这些互补的方法将创造最佳 最大限度地从再生的CST轴突中提取行为益处的策略。

PROJECT SUMMARY A major effort in regenerative neuroscience is to improve axon growth after injury to the central nervous system (CNS). Once growth is achieved, however, a second hurdle to improving function is that regenerated axons must succeed in forming synaptic contacts with appropriate sets of post-synaptic neurons. The challenge of restoring effective circuitry is especially acute after spinal injuries that damage the corticospinal tract (CST), a pathway critical for fine motor control. The CST mediates descending motor control by synapsing on specific subsets of spinal neurons, which in humans and rodents alike include a diverse set of interneurons in addition to the direct CST-motor-neuron contacts that characterize primates. The field has achieved increasing success in promoting CST axon growth, yet gains in behavioral recovery have lagged. This work will address the need to monitor the connectivity of regenerated CST axons, and to optimize their behavioral output. To do so we will employ rodent models of spinal injury and capitalize on combined stem cell bridging and viral expression of a pro-regenerative gene called KLF6, which we recently found to evoke robust regenerative CST growth. In addition, we will leverage a recently developed trans-synaptic viral labeling technique that enables an unprecedented ability to visualize post-synaptic target selection. First, we will render KLF6 expression controllable and reversible, in order to silence KLF6 after regeneration occurs in order to determine whether prolonged KLF6 expression itself interferes with behavioral recovery. This will address the pressing question of the degree to which pro-regenerative growth mechanisms may come at the expense of effective synaptic refinement or target selection. Next, we will test the ability of rehabilitative training to sculpt target selection by regenerating CSTs and improve their behavioral output. Finally, we will employ both electrical and chemogenetic means to chronically elevate activity in regenerating CST axons, which we hypothesize will both enhance CST sprouting and improve competition for synaptic territory. These complementary approaches will create optimal strategies to maximize the behavioral benefit that can be extracted from regenerated CST axons.