改造MCMV建立神经胶质特异示踪工具病毒

Neural tropic viral tools have particular advantages in neural circuit tracing. The labeling signal amplified by virus replication guarantees the good tracing effect; the viruses spreading through synapses makes it the perfect candidate for transsynaptic tracing; and the cell type specificity for virus infection provides superior potential to label specific types of neural cell. Multiple neuron tropic viral tools are applied in neural researches, but so far there is still no available glia tropic viral tool suitable for glia researches. Our previous work has demonstrated glia infection preference of murine cytomegalovirus (MCMV). The study of murine brain neural circuit tracing with MCMV-GFP also indicated their strong signal intensity, sparse labelling density and low toxicity. In addition, MCMV has other unique advantages to be developed as a glia specific tracing tool. Its large genome provides possibility for further modification, the strict infection species-specificity against murine guarantees the safety of researchers, and the combination of different MCMV derived viral tools and various Cre-transgenic mouse models further expands the application. This project is to achieve the followings: 1) using in vitro neural cell culture, microfluidic chamber and brain slice culturing system, to elucidate the infection and transporting features of the MCMV viral tool, including infection cell type preference, spreading characteristics, transsynapse ability and directions; 2) to construct a serial of MCMV derived viral tools with different labelling tags for various study purposes; 3) to establish the standard operation protocol (SOP) for glia specific labelling and glia-associated circuits tracing with MCMV derived viral tools. The successful accomplishment of this project will fill the gap in neural tracing viral tools. Our work will also provide powerful novel tools and contribute in mapping neural circuits in the brain.

嗜神经工具病毒标记神经环路具独特优势：病毒复制能放大信号，标记效果好；病毒可沿神经突触传播，实现能跨突触示踪；病毒感染有细胞选择性，适于细胞类型特异性标记。现有工具病毒均偏嗜神经元，尚缺乏适用于胶质细胞研究的工具病毒。前期工作表明鼠巨细胞病毒（MCMV）偏嗜感染胶质，MCMV-GFP可在鼠脑内清晰的标记神经胶质细胞，其信号强标记稀疏，且毒性低。此外，MCMV基因组大，提供较大改造空间；只特异性感染鼠，保障研究人员安全；可利用Cre/LoxP系统与各种Cre转基因鼠模型结合应用。本项目拟通过体外神经细胞培养、微流控培养系统、脑片培养体系，明确MCMV的细胞嗜性、传播特性、跨突触能力和方向等；基于现有的MCMV-BAC遗传改造平台，构建一系列带不同标记、适用于不同研究目的的MCMV工具病毒，并建立MCMV工具病毒示踪胶质环路的标准化方法；填补胶质研究工具的空白，为绘制脑功能联结图谱提供新工具。

嗜神经病毒可以感染神经细胞，在造成神经系统疾病的同时，也为向神经细胞转导外源基因提供了可能。多种嗜神经病毒已经被用作基因转移载体或示踪工具广泛应用于神经科学研究。但现有工具不能满足于神经科学研究的需求，顺向环路示踪工具和胶质细胞特异性转导工具仍然缺乏。因此，我们需要尝试发展满足不同科学研究需求的新的病毒工具和载体。.本研究从小鼠巨细胞病毒（MCMV）对神经细胞的高效感染能力出发，系统的比较了MCMV感染对于小鼠品系和细胞类型的偏好。发现MCMV-K181株偏嗜胶质，但对C57BL/6易感性较差。在通过基因改造构建了C57BL/6易感的MCMV重组病毒后，我们通过体外和体内测试明确了MCMV不适合作为神经环路示踪工具，但有望成为胶质细胞特异的标记和基因转移工具病毒；最后基于MCNV遗传改造平台构建了一系列MCMV重组病毒，证实了将MCMV改造为基因转移工具用于胶质细胞标记和转导的可行性；目前正在着手优化该系列工具以减小对细胞的毒性并提高病毒生产的滴度。.该项研究有望解决神经科学领域对胶质细胞难标记难转导的现状，在减毒改造成功之后有望提供一种新的病毒工具，满足神经科学对胶质细胞的研究需求。