Molecular mechanisms of activity-dependent changes in neuronal connectivity

描述（由申请人提供）：在发育期间和整个成年期，神经系统将来自环境的感觉体验转化为神经元活动的变化，进而导致突触连接和树突生长的长期改变。这一过程的中断会导致长期的不良神经后果。例如，突触数量的改变和功能可塑性反应是包括抑郁症和精神分裂症在内的许多精神健康障碍的标志[1-3]。尽管活动依赖过程在形成神经元结构方面具有重要意义，但人们对神经元兴奋性变化转化为连接改变的分子机制知之甚少。在培养的神经元中使用基于rnai的方法，我们发现GTPase Rem2是兴奋性突触发育的一种新的调节因子[4,5]。我们还证明了Rem2是一种新的即时早期基因，其转录在通过神经元去极化[6]响应钙内流时迅速上调。因此，Rem2可能是外部刺激介导神经元连接直接作用的关键分子。为了在脊椎动物模式生物的完整神经系统中验证这一假设，我建议敲除啮齿动物视觉皮层锥体神经元中的Rem2，并对这些神经元的突触接触和整体回路可塑性进行体内双光子成像

DESCRIPTION (provided by applicant): During development and throughout adulthood, the nervous system transforms sensory experience from the environment into changes in neuronal activity which, in turn, cause long-lasting alterations in synaptic connections and dendritic arborization. Disruption to this process can result in long-term undesirable neurological consequences. For example, altered synapse number and functional plasticity responses are hallmarks of a number of mental health disorders including depression and schizophrenia [1-3]. Despite the importance of activity-dependent processes in shaping neuronal architecture, little is known about the molecular mechanisms by which changes in neuronal excitability are translated into altered connectivity. Using an RNAi-based approach in cultured neurons, we identified the GTPase Rem2 as a novel regulator of excitatory synapse development [4, 5]. We have also demonstrated that Rem2 is a novel immediate early gene whose transcription is rapidly up-regulated in response to calcium influx via neuronal depolarization [6]. Thus, Rem2 may represent a key molecule through which external stimuli mediate direct effects on neuronal connectivity. To test this hypothesis in the intact nervous system of a vertebrate model organism, I propose to knockdown Rem2 in pyramidal neurons in rodent visual cortex and perform in vivo two-photon imaging of the synaptic contacts and overall circuit plasticity of these neurons while modulating visual experience. This experience-dependent in vivo approach to identify the role of Rem2 in activity-dependent neural circuit development provides an excellent opportunity to increase our understanding of genetically encoded, activity- dependent neural circuitry. Through a unique collaboration between mentors with expertise in in vivo circuit analysis, synapse development, and the molecular biology of gene regulation, I will become an expert in an impressive array of experimental techniques which will allow me to probe the function of other activity- regulated genes in the intact nervous system in the future.