Genetic Control of Phrenic Motor Neuron Development and Maintenance

呼吸是陆生脊椎动物最基本的运动行为。它的频率和幅度 呼吸运动是由位于脑干和脊髓中的神经网络控制的。在哺乳动物身上， 在吸气过程中，横隔肌的收缩对于推动气流进入肺部是必不可少的。尽管 由于调节呼吸节律的神经网络的复杂性，横隔膜的收缩是由 单个运动输入，即颈椎膈运动柱内运动神经元(MN)的活动 脊髓。PMC神经元的丢失是退行性MN疾病死亡的主要原因，如 肌萎缩侧索硬化症和脊髓损伤。尽管它们扮演着重要的角色，但分子 PMC神经元特性的决定因素在很大程度上是未知的。我们发现，PMC神经元的发育 需要Hox5转录因子的持续活性。MNS中缺乏Hox5基因的小鼠死于呼吸系统 出生失败并在PMC身份的多个方面表现出缺陷，包括细胞体位置、轴突引导 和横隔膜神经支配。在这项建议中，我们将研究Hox5基因在决定和 保持隔膜MN身份。 在目标1中，我们将确定Hox5蛋白在隔膜MN中的时间不同功能以及如何 身份在一生中都保持不变。 在目标2中，我们将定义Hox5基因如何在转录水平上控制膈MN规范。 在目标3中，我们将识别直接的Hox5效应并剖析它们的调控机制。 我们开发了一种综合的方法，包括遗传模型、高通量测序、 电生理学和行为分析，如体积描记术，在活体内解决这些问题。这个 这项建议的首要目标是揭示隔膜MN规范和 这样我们就可以开始考虑呼吸功能障碍的替代治疗方法。

Breathing is the most fundamental motor behavior for terrestrial vertebrates. The frequency and amplitude of breathing movements are controlled by neural networks residing in the brainstem and spinal cord. In mammals, contraction of the diaphragm muscle is essential for driving airflow into the lungs during inspiration. Despite the complexity of the neural networks that regulate respiratory rhythms, diaphragm contraction is controlled by a single motor input, the activity of motor neurons (MNs) within the Phrenic Motor Column (PMC) in the cervical spinal cord. Loss of PMC neurons is the primary cause of death in degenerative MN diseases such as amyotrophic lateral sclerosis (ALS) and spinal cord injuries. Despite their essential role, the molecular determinants of PMC neuron identity are largely unknown. We have found that the development of PMC neurons requires the sustained activity of Hox5 transcription factors. Mice lacking Hox5 genes in MNs die of respiratory failure at birth and exhibit defects in multiple aspects of PMC identity, including cell body position, axon guidance and diaphragm innervation. In this proposal we will investigate the function of Hox5 genes in determining and maintaining phrenic MN identity. In Aim 1 we will determine temporally distinct functions of Hox5 proteins in phrenic MNs and how phrenic MN identity is maintained throughout lifetime. In Aim 2 we will define how Hox5 genes control phrenic MN specification at the transcriptional level. In Aim 3 we will identify direct Hox5 effectors and dissect their regulatory mechanisms. We have developed an integrative methodology encompassing genetic models, high-throughput sequencing, electrophysiology and behavioral assays, such as plethysmography, to address these questions in vivo. The overarching goal of this proposal is to uncover the basic principles underlying phrenic MN specification and maintenance so that we can begin to consider alternative treatment methods for respiratory dysfunction.