Central Control of Motoneurons

描述（由申请人提供）：神经系统的大部分运动输出来自后脑和脊髓，因此了解这些区域的网络组织对于理解正常运动以及损伤或疾病对其的破坏至关重要。我们的工作重点是通过对透明斑马鱼的研究，揭示控制运动的电路发展和功能组织的基本原理，我们可以真正地观察大脑的发展，并在行为过程中对神经元的活动进行成像。年轻斑马鱼的后脑是通过一个简单的计划来构建的，总细胞类型按传递因子和转录因子排列，按年龄和功能特性排列，这可能是所有脊椎动物，包括我们自己的共同计划。拟议的工作探讨了这一计划的主要含义。年轻后脑中的神经元是根据年龄和位置来招募的，更年轻、更背侧的神经元在慢速运动中招募，而更年长的腹侧神经元在快速运动中招募。重要的是，当快速网络被吸收时，较慢网络的活动被抑制了。Aim 1的目标是在细胞水平上找到实现这种抑制的途径。网络按年龄和速度有序连接意味着电路大致按年龄顺序连接。目的2旨在探索后脑中这些年龄顺序相互作用的光遗传学程度。这种早期顺序在斑马鱼幼虫的大脑中很明显，当时它可以自由地游泳，进食和呼吸。然而，成年后脑看起来非常不同，神经元有时聚集成核，但大多数以所谓的网状结构扩散。当动物的大脑从幼小的大脑转变为成年的大脑时，它们继续产生同样的一般行为。这就提出了一个问题，一个简单的早期模式是如何随着年龄的增长而改变的，同时保持功能。在Aim 3中，我们将通过使用我们在数周内对同一条鱼进行成像的能力来解决这个问题，从而直接可视化神经元在发育过程中有序幼虫模式的迁移模式，监测它们在体内随时间的结构变化，并通过钙成像评估单个细胞随时间的功能。最后，大量的迁移必然是后脑转变的基础，这就提出了一个问题，即后脑的转变究竟有什么意义

DESCRIPTION (provided by applicant): Most of the motor output from the nervous system arises from hindbrain and spinal cord, so understanding the organization of networks in these regions is critical for understanding normal movements as well as their disruption by injury or disease. Our work focuses on revealing principles that underlie the development and functional organization of circuits controlling movement through studies of transparent zebrafish where we can literally watch the brain as it develops and image the activity of neurons during behavior. The hindbrain of young zebrafish is built via a simple plan with gross cell types arranged in columns defined by transmitter and transcription factors and arranged within columns by age and functional properties - a plan likely shared by all vertebrates, including ourselves. The proposed work explores major implications of this plan. Neurons in the young hindbrain are recruited by age and location, with younger, more dorsal ones recruited in slow movements and ventral older ones recruited with faster movements. Importantly, as faster networks are recruited, activity in slower ones is suppressed. Aim 1 is directed toward finding the pathway at the cellular level that implements this suppression. The orderly engagement of networks according to age and speed implies that circuits are wired up in a roughly age ordered way. Aim 2 is directed toward exploring optogenetically the extent of these age ordered interactions in hindbrain. This early order is evident in the larval zebrafish brain at a time when it is freely swimming, feeding and respiring. The adult hindbrain, however, looks very different with neurons sometimes clustered into nuclei, but most of them spread more diffusely in the so-called reticular formation. The animal continues to produce the same general classes of behaviors as the transformation from the young to the adult brain occurs. This raises the question of how a simple early pattern is transformed with age, while maintaining function. In Aim 3 we will address this question by using our ability to image the same fish over weeks to directly visualize patterns of migration of neurons out of the orderly larval pattern during development, monitor their structural changes over time in vivo, and assess the function of the individual cells over time with calcium imaging. Finally, the substantial migration that must underlie the transformations in hindbrain raises the question of exactly what significance there is to this migration. The facial motoneurons in hindbrain migrate a long distance caudally from their site of origin. The molecular mechanisms of this migration have been studied in depth, with the generation of migration-defective mutant lines. There is, however, almost no information about the functional consequences of this migration. In Aim 4, we will study the structure, activity, age order, and inputs to the facial motoneurons in normal fish and mutants without migration to reveal what is altered in the absence of migration and what is resilient to disruption of migration. Understanding this is critical for insight into what produces disease states, such as abnormal motor development, that are associated with disrupted migration.