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了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的发展和功能组织的基础原则，在透明斑马鱼中，我们可以真正观察大脑的发展和行为过程中神经元的活动。年轻斑马鱼的后脑是通过一个简单的计划建立的，其中总细胞类型排列在由发射器和转录因子定义的列中，并按年龄和功能特性排列在列中-这可能是所有脊椎动物共享的计划，包括我们自己。拟议的工作探讨了这一计划的主要影响。年轻的后脑神经元是根据年龄和位置招募的，年轻的、背侧的神经元在缓慢的运动中招募，腹侧的老年神经元在快速的运动中招募。重要的是，随着更快的网络被招募，较慢的网络的活动被抑制。目的1是为了找到在细胞水平上实现这种抑制的途径。网络按照年龄和速度有序地参与，这意味着电路是按照大致的年龄顺序连接的。目的2是探索光遗传学的程度，这些年龄有序的相互作用在后脑。这种早期秩序在斑马鱼幼虫的大脑中很明显，当时它正在自由游泳，进食和呼吸。然而，成年人的后脑看起来非常不同，神经元有时聚集在核中，但大多数神经元在所谓的网状结构中分布更广泛。随着从幼年大脑到成年大脑的转变，动物继续产生相同的一般行为类别。这就提出了一个问题，即一个简单的早期模式如何随着年龄的增长而转变，同时保持功能。在目标3中，我们将利用我们对同一条鱼进行数周成像的能力来解决这个问题，直接可视化神经元在发育过程中从有序的幼虫模式中迁移出来的模式，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，必须在后脑的转换提出了一个问题，究竟有什么意义， 这一迁移。面神经运动神经元从其起源地向尾侧迁移。这种迁移的分子机制已被深入研究，产生迁移缺陷突变株系。 然而，几乎没有关于这种迁移的功能后果的信息。在目标4中，我们将研究结构，活动，年龄顺序和输入的正常鱼类和突变体的面部运动神经元没有迁移，揭示什么是改变了没有迁移和什么是有弹性的迁移中断。了解这一点对于深入了解是什么导致疾病状态至关重要，例如 运动发育异常，与迁移中断有关。

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.