The Frizzled Nuclear Import Pathway in Synapse Development

描述（由申请人提供）：该项目的目标是阐明在突触发育和活动依赖性可塑性过程中受到调节的遗传程序。核功能研究的最新进展揭示了协调基因表达的核亚结构域组织中前所未有的动态。然而，调节这些动力学的生理途径在很大程度上是未知的。我们已经确定了一个关键的转导级联反应，涉及Wnt家族的成员和它的受体，在活动依赖性突触生长过程中的突触和细胞核之间的通信。Wnt在突触发育和可塑性中的重要作用也已在哺乳动物脑中被发现，并且许多认知障碍，如精神分裂症、双相情感障碍和阿尔茨海默病显示出Wnt信号传导的改变。因此，了解Wnt在大脑中的功能是一个具有重要临床意义的非常重要的领域。我们的研究表明，Wnt信号在突触激活一种新的信号通路，卷曲核输入（FNI）通路，其中Wg受体的片段，DFrizzled 2（DFz 2），被输入到细胞核。在细胞核内，该DFz 2片段与A型核纤层蛋白Lamin-C一起建立了一个专门的亚结构域，其通过控制mRNA生物合成来调节基因表达。重要的是，A型核纤层蛋白的改变涉及一组遗传性疾病，核纤层蛋白病，其对神经肌肉系统的功能具有破坏性影响。在这个项目中，我们建议调查的功能，这个核子域的活动依赖性突触可塑性。特别是，我们建议（1）确定核亚结构域在控制核mRNA聚腺苷酸化中的作用，并确定受此途径调节的基因，（2）确定运动神经元刺激过程中核亚结构域的动力学，（3）开始表征受此转导级联调节的重要基因。我们预测，这些研究将是非常重要的，我们了解突触事件是如何沟通到细胞核，以调节基因表达。最终，我们期望所提出的研究将与我们对与Wnt信号传导障碍相关的认知障碍的理解高度相关，并确定在核纤层蛋白病中改变的细胞事件。 公共卫生相关性：神经系统中突触连接的一个基本特性是它们响应经验而改变的能力，这一过程被称为突触可塑性。对许多系统的研究表明，这一事件背后的机制依赖于细胞核内基因的调控。因此，重要的研究工作一直致力于了解突触连接如何与细胞核通信。在我们的研究中，我们发现了一种新的信号通路，至少部分地介导了这种通信。该通路涉及蛋白质家族的成员，Wnts及其受体，其对于突触连接的发展是至关重要的。这些发现特别重要，因为在人类中Wnt信号的改变与认知障碍有关，如精神分裂症，双相情感障碍和阿尔茨海默病。因此，了解这一途径可能会对这些疾病的原因提供重要的见解。我们还发现，Wnt信号通路与核蛋白，A型核纤层蛋白，在基因表达的调控。有趣的是，A型核纤层蛋白的改变导致神经肌肉系统的毁灭性疾病。在这个项目中，我们将确定由Wnt和A型核纤层蛋白调控的基因，检查完成这种调控的核区域的特性，并开始表征突触发育和可塑性中受调控基因的功能。这些研究将在一个强大的模型系统中进行，该系统适用于复杂的遗传技术，果蝇，预计将为我们理解经验改变大脑中突触连接的过程提供重大进展。此外，通过阐明这些事件背后的机制，我们希望有助于临床策略的发展，以改善或治愈与Wnt信号传导功能障碍相关的层粘连蛋白病和认知障碍。

DESCRIPTION (provided by applicant): The goal of this project is to elucidate the genetic programs that are regulated during synaptic development and activity-dependent plasticity. Recent advances in the study of nuclear functions reveal an unprecedented dynamics in the organization of nuclear subdomains which coordinate gene expression. However, the physiological pathways that regulate these dynamics are largely unknown. We have identified a critical transduction cascade, involving a member of the Wnt family and its receptor, in the communication between the synapse and the nucleus during activity-dependent synaptic growth. Essential roles of Wnts in synapse development and plasticity have also been uncovered in the mammalian brain, and a number of cognitive disorders, such as schizophrenia, bipolar disorder, and Alzheimer's disease show alterations in Wnt signaling. Thus, understanding how Wnts function in the brain is a highly significant area with important clinical implications. Our studies demonstrate that Wnt signaling at synapses activates a novel signaling pathway, the Frizzled Nuclear Import (FNI) pathway, in which a fragment of the Wg receptor, DFrizzled2 (DFz2), is imported into the nucleus. Within the nucleus, this DFz2 fragment, together with the A-type lamin, Lamin-C, establishes a specialized subdomain, which regulates gene expression by controlling mRNA biogenesis. Importantly, alterations in A-type lamins have been involved in a group of hereditary disorders, the laminopathies, which have devastating impact on the function of the neuromuscular system. In this project we propose to investigate the function of this nuclear subdomain in activity-dependent synaptic plasticity. In particular, we propose to (1) determine the role of the nuclear subdomain in controlling nuclear mRNA polyadenylation and to identify the genes that are regulated by this pathway, (2) determine the dynamics of the nuclear subdomain during motorneuron stimulation, and (3) begin the characterization of an important gene regulated by this transduction cascade. We predict that these studies will be highly significant for our understanding of how synaptic events are communicated to the nucleus to regulate gene expression. Ultimately, we expect that the proposed studies will be highly relevant to our understanding of cognitive disorders associated with the malfunction of Wnt signaling and to identify the cellular events that are altered in laminopathies. PUBLIC HEALTH RELEVANCE: A fundamental property of synaptic connections in the nervous system is their ability to change in response to experiences, a process that is referred to as synaptic plasticity. Studies in many systems show that a mechanism underlying this event relies on the regulation of genes within the nucleus. Thus, significant research efforts have been dedicated to understanding how synaptic connections communicate with the nucleus. In our research, we have uncovered a novel signaling pathway that, at least in part, mediates this communication. This pathway involves a member of a protein family, the Wnts and its receptor, which appears fundamental for the development of synaptic connections. These finding are particularly important, given that in humans alterations in Wnt signaling are associated with cognitive disorders, such as schizophrenia, bipolar disorder, and Alzheimer's disease. Thus, understanding this pathway may provide important insight into the causes of these conditions. We have also found that the Wnt signaling pathway collaborates with a nuclear protein, an A-type lamin, in the regulation of gene expression. Interestingly, alterations in A-type lamins lead to devastating diseases of the neuromuscular system. In this project we will identify the genes that are regulated by Wnts and A-type lamins, examine the properties of a nuclear region where this regulation is accomplished, and begin to characterize the function of the regulated genes in synapse development and plasticity. These studies, which will be conducted in a powerful model system amenable to sophisticated genetic techniques, the fruit fly Drosophila, is expected to provide significant advances to our understanding of the processes by which experiences modify the synaptic connections in the brain. In addition, by elucidating the mechanisms underlying these events, we hope to contribute to the development of clinical strategies to ameliorate or cure laminopathies and cognitive disorders associated with malfunction of Wnt signaling.