Extracellular Matrix and Neuromuscular Development

描述（由申请人提供）：神经元和它们的目标交换信息的许多种类的突触的形成，维持和修改。我们使用简单易行的骨骼神经肌肉接头来鉴定介导这种交换的分子和机制。初步研究表明，运动神经元和肌管产生的一些线索与占据这两个细胞之间突触间隙的基底层（BL）稳定相关。随后，我们和其他人确定了几个BL相关的信号，然后我们在小鼠中使用基因靶向来询问哪些在体内起关键作用。通过这种方式，我们发现Z-聚集蛋白是神经源性的突触后分化的组织者，并使用聚集蛋白作为起点来阐明突触后分化的基本途径。现在，我们将重点放在突触前分化，并寻求相应的逆行信号通路。这里的出发点是我们发现β 2层粘连蛋白是BL相关的、肌肉来源的线索，其是神经末梢成熟所需的，但对于它们的初始分化是不可缺少的。我们最近发现了几种层粘连蛋白可能相互作用或合作的分子，并建议分析它们的作用。（i）由于β 2层粘连蛋白对突触形成很重要，我们寻找了它的突触受体，发现它们包括神经末梢的电压门控钙通道。 (ii)由于β 2层粘连蛋白不是单独作用的，我们寻找其他突触前组织分子，并发现了四种：FGF-22，P84/SIRP-α和两种来自电鳐电器官的新蛋白。我们现在将使用阻断剂和基因靶向来找出这些成分在体内神经肌肉接头中发挥的作用。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报告者来记录生长锥转化为运动神经末梢的步骤顺序。通过这项工作，我们希望深入了解突触构建的基本原理，突触是所有神经功能的基本信息处理单元。我们的研究结果将与运动神经末梢疾病（如Lambert-Eaton综合征）直接相关，还将为调节不易接近的中枢神经末梢形成的机制提供见解，这些中枢神经末梢可能是神经系统和精神疾病的功能障碍部位

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