Visualizing BDNF cell-to-cell transfer and its effects on synapse and circuit function

可视化 BDNF 细胞间转移及其对突触和电路功能的影响

• 批准号: 422153908
• 负责人: Dr. Camin Dean
• 金额: --
• 依托单位: Standort Berlin
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/422153908?language=en
• 关键词: Visualizing; BDNF; cell; transfer; its

Brain-derived neurotrophic factor (BDNF) is essential for neuronal growth, differentiation, and synaptic plasticity. The release of BDNF from neurons, and the effects of BDNF on neuron and circuit function, have both been well-studied separately, where transfer of BDNF from neurons to other neurons has been assumed. But to date, the transfer of BDNF between cells has not been directly visualized and investigated. Using a four-fluorophore imaging approach to identify both the cell of origin and target cells, we quantified the transfer of BDNF between cells. Surprisingly, in preliminary data, we found that astrocytes appear to be the main recipient of neuronally expressed BDNF. We further found that astrocytes specifically take up mature (not pro) BDNF that is released by neurons. Over-expression of the TrkB receptor in neurons redirected released BDNF from astrocytes to neurons, suggesting that TrkB levels determine neuronal versus astrocytic BDNF uptake. In addition, increased neuronal activity further increased astrocytic (but not neuronal) uptake of neuronally expressed BDNF. Finally, we also found in preliminary experiments, that astrocytes do not simply act as a sink or buffer for excess BDNF, as previously proposed, but rather that BDNF taken up by astrocytes mediates physiological effects by increasing astrocytic territory. The goal of this project is to extend these initial observations to, 1) examine and quantify the transfer of endogenous BDNF from neurons to astrocytes in vivo - using CRISPR/Cas9 to label endogenous BDNF in the brain, 2) determine if astrocytic uptake of neuronal BDNF, and subsequent increases in astrocytic territory, are mediated by the TrkB.T1 receptor (the main BDNF receptor expressed in astrocytes) - using astrocyte-specific TrkB.T1 knockout mice, and 3) determine if the transfer of BDNF from neurons to astrocytes is necessary for aspects of synapse and circuit function - using optical readouts of synaptic strength and electrophysiological recordings. Together the proposed experiments will confirm and substantiate an unexpected function of BDNF, whereby it can affect synapse and circuit function in the brain via astrocytes, by changing astrocyte morphology.

脑源性神经营养因子 (BDNF) 对于神经元生长、分化和突触可塑性至关重要。神经元释放 BDNF 以及 BDNF 对神经元和回路功能的影响都已分别得到充分研究，其中假设 BDNF 从神经元转移到其他神经元。但迄今为止，细胞间 BDNF 的转移尚未被直接观察和研究。 使用四荧光团成像方法来识别起源细胞和靶细胞，我们量化了 BDNF 在细胞之间的转移。令人惊讶的是，在初步数据中，我们发现星形胶质细胞似乎是神经元表达的 BDNF 的主要受体。我们进一步发现星形胶质细胞特异性吸收神经元释放的成熟（而非原）BDNF。神经元中 TrkB 受体的过度表达将释放的 BDNF 从星形胶质细胞重新定向到神经元，这表明 TrkB 水平决定神经元与星形胶质细胞的 BDNF 摄取。此外，神经元活动的增加进一步增加了星形胶质细胞（但不是神经元）对神经元表达的 BDNF 的摄取。最后，我们在初步实验中还发现，星形胶质细胞并不像之前提出的那样简单地充当过量 BDNF 的接收器或缓冲器，而是星形胶质细胞吸收的 BDNF 通过增加星形胶质细胞的区域来介导生理效应。 该项目的目标是将这些初步观察扩展到，1）检查和量化体内内源性 BDNF 从神经元到星形胶质细胞的转移 - 使用 CRISPR/Cas9 标记大脑中的内源性 BDNF，2）确定星形胶质细胞对神经元 BDNF 的摄取以及随后星形胶质细胞区域的增加是否由 TrkB.T1 受体（主要 星形胶质细胞中表达的 BDNF 受体） - 使用星形胶质细胞特异性 TrkB.T1 敲除小鼠，3）确定 BDNF 从神经元到星形胶质细胞的转移对于突触和电路功能方面是否是必要的 - 使用突触强度的光学读数和电生理记录。这些实验将共同证实和证实 BDNF 的意想不到的功能，即它可以通过星形胶质细胞改变星形胶质细胞的形态来影响大脑中的突触和回路功能。