Optogenetic activation of receptors has advantages compared with chemical or ligand treatment because of its high spatial and temporal precision. Especially in the brain, the use of a genetically encoded light-tunable receptor is superior to direct infusion or systemic drug treatment. We applied light-activatable TrkB receptors in the mouse brain with reduced basal activity by incorporating Cry2PHR mutant, Opto-cytTrkB(E281A). Upon AAV mediated gene delivery, this form was expressed at sufficient levels in the mouse hippocampus (HPC) and medial entorhinal cortex (MEC) retaining normal canonical signal transduction by the blue light stimulus, even by delivery of noninvasive LED light on the mouse head. Within target cells, where its expression was driven by a cell type-specific promoter, Opto-cytTrkB(E281A)-mediated TrkB signaling could be controlled by adjusting light-stimulating conditions. We further demonstrated that Opto-cytTrkB(E281A) could locally induce TrkB signaling in axon terminals in the MEC-HPC. In summary, Opto-cytTrkB(E281A) will be useful for elucidating time- and region-specific roles of TrkB signaling ranging from cellular function to neural circuit mechanisms.

中文翻译：

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小鼠脑中TrkB信号的光遗传调控。

受体的光遗传激活与化学或配体处理相比具有优势，因为它具有很高的时空精度。特别是在大脑中，使用基因编码的光可调受体优于直接输注或全身药物治疗。我们通过掺入Cry2PHR突变体Opto-cytTrkB（E281A）在小鼠脑中应用了光激活性TrkB受体，降低了基础活动。在AAV介导的基因传递后，这种形式在小鼠海马（HPC）和内侧内嗅皮层（MEC）中以足够的水平表达，即使通过在小鼠头上传递无创LED光，也可以通过蓝光刺激保持正常的规范信号转导。在靶细胞中，其表达受细胞类型特异性启动子驱动，光cytTrkB（E281A）介导的TrkB信号可以通过调节光刺激条件来控制。我们进一步证明，Opty-cytTrkB（E281A）可以在MEC-HPC的轴突末端局部诱导TrkB信号传导。总之，Opty-cytTrkB（E281A）对于阐明从细胞功能到神经回路机制的TrkB信号在时间和区域上的特定作用将非常有用。