Extracellular Matrix and Neuromuscular Development

描述（由申请人提供）：神经元和它们的目标在突触形成、维持和修改的过程中交换多种信息。我们使用简单和易于接近的骨骼神经肌肉连接点来识别介导这种交换的分子和机制。最初的研究表明，运动神经元和肌管产生的一些信号与占据这两个细胞之间突触间隙的基底膜（BL）稳定相关。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靶向来询问哪些在体内发挥关键作用。通过这种方式，我们发现z-agrin是突触后分化的神经来源组织者，并以agrin为起点阐明了突触后分化的基本途径。现在，我们将重点关注突触前分化，并寻求相应的逆行信号通路。这里的出发点是我们的发现，β 2层粘连蛋白是bl相关的，肌肉来源的线索，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。我们最近发现了几个可能与层粘连蛋白相互作用或合作的分子，并提出分析它们的作用，(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。

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