Respiratory Circuit Dysfunction in Rett Syndrome

描述（由申请人提供）：Rett综合征（RTT）是一种复杂的自闭症谱系障碍（ASD），由MECP 2基因突变引起，影响全球约1/10，000活产女性。除了认知、运动和行为缺陷外，RTT最严重的身体衰弱后果之一是呼吸控制严重中断，高达25%的RTT患者可能因心肺并发症过早死亡。目前，对于RTT中的呼吸障碍或任何其他神经功能缺损没有可用的治疗方法。我们对RTT中呼吸功能障碍的神经机制的理解受到以下事实的阻碍，即我们仍然对MECP 2的丧失如何影响特定脑干呼吸回路中的神经元和/或突触功能知之甚少。因此，拟议的研究采用多学科方法来定义MECP 2的遗传丢失如何破坏呼吸控制，重点是使用明确的疾病小鼠模型调节脑干中关键呼吸反射通路的兴奋-抑制平衡。将在体外脑干切片中使用电生理学方法来测试以下假设：调节对缺氧和肺膨胀的反射反应的初级传入突触的兴奋性增加有助于RTT中的呼吸回路功能障碍，并定义潜在机制。我们还将研究如何在脑源性神经营养因子（BDNF），一个关键的神经元信号分子，其表达在RTT严重下降，赤字有助于突触功能障碍，以及增强BDNF信号分子的能力，恢复正常功能在RTT小鼠在体外和体内。此外，我们将使用Fos免疫染色来绘制整个脑干呼吸网络中神经元和/或突触功能在体内被破坏的部位。最后，我们将研究人类BDNF基因Val 66 Met-BDNF的常见多态性如何影响小鼠呼吸道症状的严重程度和对BDNF靶向治疗的治疗反应。拟议的研究旨在使用创新的实验方法和小鼠模型来定义RTT中呼吸功能障碍的机制。通过关注突触兴奋性，特别是BDNF介导的信号传导，希望这些研究将促进RTT中呼吸障碍的新治疗策略的发展。此外，我们希望从RTT电路功能障碍的分析中获得的见解将广泛适用于ASD作为一个整体。

DESCRIPTION (provided by applicant): Rett syndrome (RTT) is a complex Autism Spectrum Disorder (ASD) that is caused by mutations in the MECP2 gene and affects approximately 1 in 10,000 live female births worldwide. In addition to cognitive, motor and behavioral deficits, one of the most physically debilitating consequences of RTT is severe disruption in the control of breathing, and up to 25% of RTT patients may die prematurely of cardiorespiratory complications. Currently, there are no treatments available for breathing disorders, or any other neurologic deficits in RTT. Our understanding of neural mechanisms that underlie respiratory dysfunction in RTT is hampered by the fact that we still know little about how loss of MECP2 affects neuronal and/or synaptic function in specific brainstem respiratory circuits. Therefore, the proposed research takes a multidisciplinary approach to define how genetic loss of MECP2 disrupts respiratory control, focusing on modulation of excitatory-inhibitory balance in key respiratory reflex pathways in the brainstem using a well-defined mouse model of the disease. Electrophysiological methods will be used in brainstem slices in vitro to test the hypothesis that increased excitability at primary afferent synapses regulating reflex responses to hypoxia and lung inflation contributes to respiratory circuit dysfunction in RTT and to define underlying mechanisms. We will also examine how deficits in Brain Derived Neurotrophic Factor (BDNF), a key neuronal signaling molecule whose expression is severely decreased in RTT, contribute to synaptic dysfunction, as well as the ability of molecules that enhance BDNF signaling to restore normal function in RTT mice in vitro and in vivo. In addition, we will use Fos immunostaining to map sites throughout the brainstem respiratory network at which neuronal and/or synaptic function is disrupted in vivo. Finally, we will examine how a common polymorphism in the human BDNF gene, Val66Met-BDNF, influences the severity of respiratory symptoms and the therapeutic response to BDNF- targeted therapies in mice. The proposed research aims to define mechanisms that underlie respiratory dysfunction in RTT using innovative experimental approaches and mouse models. By focusing on synaptic excitability, and BDNF-mediated signaling in particular, it is hoped these studies will foster development of new therapeutic strategies for breathing disorders in RTT. Moreover, it is hoped that insights obtained from analysis of circuit dysfunction in RTT will be broadly applicable to ASDs as a whole.