Role of the Serine/Threonin Kinase Ndr2 in Integrin-mediated Neural Plasticity and Learning

整合素介导的细胞黏附和信号转导在中枢神经系统发育和成年神经可塑性中起重要作用。特别是，有证据表明，β1整合素在海马区的长时程增强和海马区依赖的工作记忆任务中发挥了作用。然而，控制整合素在神经细胞表面表达和激活的机制仍远未被了解。我们最近发现，丝氨酸/苏氨酸激酶NDR2是β1整合素运输及其在神经元分化过程中的表面表达的调节因子。NDR2是河马信号通路的靶标，在应激时表达增加，从而控制海马神经元中树突的生长和分支。为了进一步研究NDR2/β1-整合素相互作用在体内的作用，我们培育了NDR2结构性或条件性缺陷的新型突变小鼠。我们的初步数据表明，NDR2在体内也控制着海马锥体细胞的树突分支，以及在海马体依赖的学习任务中的工作/短期记忆。在这个项目中，我们结合了我们在行为遗传学和分子神经生物学(STOK)以及细胞和系统生理学(Dityatev)方面的专业知识，深入分析了NDR2/beta1-整合素在结构和功能突触可塑性和记忆形成中的相互作用。我们将利用最先进的技术，包括激光显微解剖和双光子显微镜，来确定与可塑性和记忆形成有关的分子激活过程和突触动力学。因此，我们将研究NDR2在海马体发育过程中的表达，以及对持续改变海马体电路的应激源的反应。我们将从生化水平阐明NDR2消融对海马β1整合素活化和β1整合素依赖信号的影响，并仔细研究NDR2缺陷小鼠海马神经元的形态和生理特性的变化。这将为深入了解NDR2/Beta1整合素在海马突触中的作用机制提供一个框架，并为理解它们在海马依赖任务中的工作记忆中的作用提供一个框架，这将是我们对NDR2突变小鼠进行全面行为分析的重点。我们进一步的目的是剖析NDR2/β1-整合素相互作用在发育和急性突触调节中的作用。为此，我们将使用我们的新的条件NDR2突变体和不同的Cre重组酶驱动系来靶向出生后发育和成年期的海马主细胞。沿着同样的思路，我们将研究依赖NDR2的细胞过程与青少年和成年期应激暴露的衰弱效应的相关性，并将通过急性整合素刺激来检测NDR2缺陷小鼠突触可塑性和学习能力的潜在恢复。

Integrin-mediated cell adhesion and signaling are critically involved in the development of the central nervous system and in neural plasticity in the adult. In particular, evidence suggests a role of beta1-integrins in hippocampal long-term potentiation and in hippocampus-dependent working memory tasks. However, the mechanisms that control the surface expression and activation of integrins in neuronal cells are still far from understood. We have recently identified the serine/threonine kinase Ndr2 as a regulator of beta1-integrin trafficking and its surface expression during neuronal differentiation. Ndr2, a target of the Hippo signaling pathway that is increased in expression upon stress, thereby controls dendritic growth and branching in hippocampal neurons. To further investigate the role of Ndr2/beta1-integrin interaction in vivo we have developed novel mutant mice that are constitutively or conditionally deficient in Ndr2. Our preliminary data suggest that Ndr2 also controls the dendritic branching of hippocampal pyramidal cells in vivo as well as working / short-term memory in hippocampus-dependent learning tasks. In this project we have teamed up to combine our expertise in behavioral genetics and molecular neurobiology (Stork) as well as cell- and systems physiology (Dityatev) for an in-depth analysis of the Ndr2/beta1-integrin interaction in structural and functional synaptic plasticity and memory formation. We will utilize state-of-the art technology, including laser microdissection and 2-photon microscopy, to determine molecular activation processes and synapse dynamics in relation to plasticity and memory formation. Thereby we will examine Ndr2 expression during hippocampal development and in response to stressors that lastingly alter the hippocampal circuitry. We will clarify the effect of Ndr2 ablation on beta1-integrin activation and beta1-integrin-dependent signaling in the hippocampus on a biochemical level and carefully examine the altered morphological and physiological properties of hippocampal neurons of Ndr2 deficient mice. This shall provide insight into the mechanisms of Ndr2/beta1-integrin action at hippocampal synapses and a framework for understanding their role in working memory in hippocampus-dependent tasks, which will be at the focus of our comprehensive behavioral analysis of the Ndr2 mutant mice. We further aim to dissect the role of Ndr2/beta1-integrin interaction in development and acute synaptic regulation. To this end we will employ our novel conditional Ndr2 mutants and different CRE recombinase driver lines targeting hippocampal principle cells during postnatal development and adulthood. Along the same line, we will investigate the relevance of Ndr2-dependent cellular processes for the debilitating effects of stress exposure in juvenility and adulthood and will examine the potential recovery of synaptic plasticity and learning in Ndr2 deficient mice through acute integrin stimulation.