Extracellular Matrix and Neuromuscular Development

描述(申请人提供)：神经元和它们的目标在突触形成、维持和修改时交换许多类型的信息。我们使用简单和可接近的骨骼神经肌肉连接来识别调节这种交换的分子和机制。初步研究表明，运动神经元和肌管所阐述的一些线索与占据这两个细胞之间的突触间隙的基底板(BL)有稳定的联系。随后，我们和其他人确定了几个与BL相关的信号，然后我们在小鼠中使用基因打靶来询问哪些信号在体内发挥了关键作用。通过这种方式，我们发现z-agrin是突触后分化的神经源性组织者，并以agrin为起点阐明了突触后分化的基本途径。现在，我们将重点放在突触前分化上，并寻找相应的逆行信号通路。这里的起点是我们发现，Beta2层粘连蛋白是BL相关的、肌肉衍生的信号，是神经末梢成熟所必需的，但对于它们的初始分化是必不可少的。我们最近确定了几个层粘连蛋白可能相互作用或协同作用的分子，并建议分析它们的作用，(1)由于层粘连蛋白β2对突触的形成很重要，我们寻找它的突触受体，发现它们包括神经末梢的电压门控钙通道。 (Ii)由于β2层粘连蛋白不是单独作用的，我们寻找了其他突触前组织分子，发现了四个：成纤维细胞生长因子-22、P84/SIRP-α和两个来自鱼雷电器官的新蛋白。我们现在将使用阻断试剂和基因打靶来找出这些成分在体内神经肌肉连接处扮演的角色。此外，为了正确解释这些机制研究，我们将使用新的成像方法和转基因记者来记录生长锥转化为运动神经末梢的步骤序列。通过这项工作，我们希望深入了解突触构建的原理，突触是构成所有神经功能的基本信息处理单位。我们的结果将直接与运动神经末梢的疾病相关，如兰伯特-伊顿综合症，并将为调节较难到达的中枢神经末梢的形成机制提供见解，这些神经末梢可能是神经和精神疾病的故障部位

DESCRIPTION (provided by applicant): Neurons and their targets exchange information of many sorts as synapses are formed, maintained and modified. We use the simple and accessible skeletal neuromuscular junction to identify molecules and mechanisms that mediate this exchange. Initial studies showed that some cues elaborated by motoneurons and myotubes are stably associated with the basal lamina (BL) that occupies the synaptic cleft between these two cells. Subsequently, we and others identified several BL-associated signals, and we then used gene targeting in mice to ask which played critical roles in vivo. In this way, we found that z-agrin is a nerve-derived organizer of postsynaptic differentiation and used agrin as a starting point to elucidate a rudimentary pathway for postsynaptic differentiation. Now, we will focus on presynaptic differentiation, and seek a corresponding retrograde signaling pathway. The starting point here is our finding that beta2 laminins are BL-associated, muscle-derived cues that are required for nerve terminal maturation but dispensable for their initial differentiation. We recently identified several molecules that laminin may interact or cooperate with, and propose to analyze their roles, (i) Because beta2 laminins are important for synapse formation, we sought its synaptic receptors, and found that they include the voltage-gated calcium channels of the nerve terminal. (ii) Because beta2 laminins do not act alone, we sought other presynaptic organizing molecules, and found four: FGF-22, P84/SIRP-alpha, and two novel proteins from Torpedo electric organ. We will now use blocking reagents and gene targeting to find out what roles these components play at the neuromuscular junction in vivo. In addition, so we can properly interpret these mechanistic studies, we will use new imaging methods and transgenic reporters to document the sequence of steps by which a growth cone is transformed into a motor nerve terminal. Through this work, we hope to gain insight into principles that underlie construction of synapses, which are the fundamental information-processing units that underlie all neural function. Our results will be directly relevant to diseases of the motor nerve terminal, such as Lambert-Eaton Syndrome, and will also provide insights into mechanisms that regulate formation of less accessible central nerve terminals, which may be sites of malfunction in both neurological and psychiatric disorders