Cellular and Molecular Mechanisms Underlying Trophic Factor-Mediated Inhibitory Synapse Formation

所有动物的行为--从简单的反射到复杂的运动模式，以及学习和记忆--都严重依赖于在早期发育过程中建立的精确连接模式。由于遗传或环境因素的干扰，这种突触连接会导致神经系统功能失调，并导致自闭症谱系或阿尔茨海默病等大脑疾病。细胞外环境中存在的营养分子调节脑细胞连通性的许多重要方面。营养因子调节数百亿个神经元之间的连接模式的确切细胞和分子机制仍然存在，尽管目前还不清楚，部分原因是哺乳动物大脑中复杂的神经元网络形成。因此，我将使用一个更简单的模型系统--淡水池塘蜗牛，在那里可以研究功能定义的单个突触前和突触后神经元之间连接的形成。与众所周知的营养因子在兴奋性连接形成中的作用不同，人们对抑制性突触形成几乎一无所知。这一信息尤其重要，因为抑制性突触形成的障碍或它们的扰动会导致兴奋和抑制之间的失衡，从而与自闭症谱系、癫痫和精神分裂症等大脑疾病有关。在这项研究中，我将利用突触前和突触后单个神经元之间的体外重建连接，结合几项最先进的神经科学技术，如神经元硅芯片、电生理学、药理学、共聚焦显微镜和RNAi技术，重点研究营养因子在抑制性突触形成中的作用。从这项研究中获得的知识将有助于我们努力修复中风、损伤后的脑损伤，并治疗神经退行性疾病。这也将有助于我们在加拿大进一步发展芯片技术，并促进其商业化。

All animal behaviors - ranging from simple reflexes to complex motor patterns, and learning and memory rely critically upon precise connectivity patterns that are established during early development. Perturbation of this synaptic connectivity either due to genetical or environmental factors renders the nervous system dysfunctional and results in brain disorders such as the Autism spectrum or Alzheimer's diseases. Trophic molecules present in the extracellular milieu regulate many important aspects of brain cell connectivity. The precise cellular and molecular mechanisms by which trophic factors regulate the connectivity patterns between tens of billions of neurons remain, however poorly defined, due partially to the complex neuronal network formation in the mammalian brain. I will thus use a simpler model system, the fresh water pond snail, Lymnaea stagnalis where the formation of connectivity between functionally defined single pre- and postsynaptic neurons can be studied. In contrast to the well known action of trophic factors in excitatory connectivity formation, virtually nothing is known about inhibitory synapse formation. This information is particularly important because disturbance of inhibitory synapse formation or their perturbations result in an imbalance between excitation and inhibition, and hence have been linked to brain disorders such as autism spectrum, epilepsy and schizophrenia etc. In this study, I will thus focus on the role of trophic factors in inhibitory synapse formation by taking advantage of the in vitro reconstructed connectivity between single pre- and postsynaptic Lymnaea neurons, coupled with several state-of the-art neuroscience techniques such as the neuron silicon chip, electrophysiological, pharmacological, confocal microscopy and RNAi techniques. The knowledge gained from this study will help our efforts in repairing brain damage after stroke, injury and in treating neurodegenerative diseases. It will also help us develop further the chip technology in Canada and facilitate its commercialization.