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

整合素介导的细胞粘附和信号传导在中枢神经系统的发育和成人的神经可塑性中起关键作用。特别是，有证据表明β 1-整合素在海马长时程增强和海马依赖性工作记忆任务中的作用。然而，控制神经细胞中整合素的表面表达和活化的机制仍远未被理解。我们最近已经确定了丝氨酸/苏氨酸激酶Ndr 2作为β 1-整联蛋白运输及其在神经元分化过程中的表面表达的调节剂。Ndr 2是Hippo信号通路的靶点，在应激时表达增加，从而控制海马神经元中的树突生长和分支。为了进一步研究Ndr 2/β 1-整联蛋白相互作用在体内的作用，我们已经开发了组成性或条件性缺乏Ndr 2的新型突变小鼠。我们的初步数据表明，Ndr 2还控制在体内海马锥体细胞的树突状分支以及在海马依赖性学习任务中的工作/短期记忆。在这个项目中，我们已经合作了联合收割机结合我们在行为遗传学和分子神经生物学（鹳）以及细胞和系统生理学（Dityatev）的专业知识，深入分析了结构和功能突触可塑性和记忆形成中的Ndr 2/β 1-整合素相互作用。我们将利用最先进的技术，包括激光显微切割和双光子显微镜，以确定分子激活过程和突触动力学与可塑性和记忆形成。因此，我们将研究海马发育过程中的Ndr 2表达，并对持久改变海马电路的应激源作出反应。我们将阐明Ndr 2消融对海马中β 1-整合素激活和β 1-整合素依赖性信号传导的影响，并在生化水平上仔细研究Ndr 2缺陷小鼠海马神经元的形态学和生理学特性的改变。这将提供深入了解Ndr 2/β 1-整合素在海马突触的作用机制，并为理解它们在工作记忆中的作用提供框架，这将是我们对Ndr 2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Ndr 2/β 1-整合素相互作用的发展和急性突触调节的作用。为此，我们将在出生后发育和成年期间采用我们的新型条件性Ndr 2突变体和不同的CRE重组酶驱动系靶向海马主细胞。沿着相同的路线，我们将调查Ndr 2依赖性细胞过程的相关性，在幼年和成年期的压力暴露的衰弱效应，并将检查通过急性整合素刺激Ndr 2缺陷小鼠突触可塑性和学习的潜在恢复。

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.