神经环路网络的构建是大脑发育的关键步骤。环路连接的精准调控对于情感，认知和神经精神疾病的病理至关重要。腹侧海马（vHPC）和其相连长程投射参与调控情感和记忆，但其形成和整合的分子机制仍不明确。miR-135是大脑富集的microRNA。我们前期研究发现miR-135在海马神经元轴突表达，降低突触前末梢数量，抑制CA3-CA1投射突触前膜的成熟。故我们假设miR-135调节vHPC长程传出通路，从而参与调控情感和记忆。我们已构建Camk2a-tTA/miR-135TG小鼠，可在兴奋性神经元诱导miR-135表达。结合病毒示踪，计算机三维重构，光遗传学和电生理手段，将阐明miR-135调控海马神经元突触前末梢发育和功能的机理；明确miR-135在vHPC传出投射构建及情绪和记忆中的作用。本研究将揭示早期基因改变对成体大脑环路构建和功能的影响，发现神经精神疾病中认知受损和情感障碍的分子环路机制。

The wiring of neural circuit is a critical step during brain development. The precise wiring during neural development underlies cognition, emotion, and circuit pathology of brain disorders. Ventral Hippocampus (vHPC) and the connected neural networks, such as projections from vHPC to medial prefrontal cortex (mPFC), nucleus accumbens (NAc), and amygdala (AMY) play important role in emotion, stress response, learning and memory. The disturbance in vHPC efferent pathway is involved in mood and cognitive disorders associated with many neuropsychiatric diseases. However, the molecular mechanisms for the establishment and fine-tuning of vHPC projection pathways remain largely unknown. Our recent research showed that miR-135, a brain enriched microRNA, locates on axon, and it restricts the presynaptic site development in hippocampal neuron and maturation of hippocampal CA3-CA1 pathway. During the period of synaptogenesis, a reduction in miR-135 leads to increased expression of its target genes complexin-1 and -2, and the complexins in turn promote presynaptic site development in ventral hippocampus. Based on these findings, we propose that miR-135 is involved in the establishment of efferent long-term projections of vHPC and the associated behavioral responses, such as emotion, learning and memory. We have generated the Camk2a-tTA/miR-135TG mouse, in which miR-135 is overexpressed in the forebrain excitatory neuron. We will also use viral genetic tools to fulfil brain region-specific and circuit-specific manipulation of miR-135 and its targets in wild type mouse. With these animal models, we aim to investigate whether and how miR-135 regulates vHPC-mPFC, vHPC-NAc, and vHPC-AMY pathways, as well as the underling emotion and cognition. This microRNA-dependent presynaptic modulation of vHPC projections will provide novel insight to understand the mechanism of development and organization of brain circuit. Moreover, this proposal will elucidate the neurobiological basis for circuitry psychopathologies and provide the novel clinical interventions for treatment of emotional and cognitive dysfunction in neuropsychiatric disorders.