BRAIN EAGER: Novel Targeting Strategies for Projection-specific Mapping of Neurons

神经科学的一个中心目标是从特定神经元的活动和连接性方面理解行为。解剖学追踪揭示了大脑中的中尺度连接，但这个数据集缺乏功能实用性，无法从行为上研究与其他大脑区域有特定连接的神经元。最近，许多技术进步使这些类型的实验成为可能，包括重新设计病毒以靶向特定神经元类型并传递感兴趣的基因。这种方法很重要，因为特定神经元的遗传靶向允许人们在神经元的解剖结构（它投射到的区域）和它的功能（它编码的信息）之间建立联系。该项目将探索新工具的工程设计，这些工具将显着改善现有的逆行追踪技术，从而将行为功能映射到特定的神经元类型。由此产生的工具将广泛提供给社区，以增加其影响和utility.As系统神经科学正在采用来自分子生物学的工具，有一个电路特定的技术的重要性越来越多的赞赏，例如针对神经元类型定义的预测使用逆行病毒策略的解剖和遗传标记。这些工具对于使用遗传活性指标进行细胞类型特异性记录或使用光遗传学致动器进行控制至关重要。然而，现有逆行病毒的效率和可变向性（即不能靶向所有细胞类型）对这些实验方法提出了挑战。为了克服这一挑战，提出了两种方法来产生将提供无毒特性同时最大化目标群体的有效标记的试剂。这些方法将利用病毒内化的分子机制来克服向性，以及使用新的蛋白质连接技术改进的经典示踪剂。这些试剂将适用于精确和稳健的解剖学追踪，用于诱导光致和化学致动器。因此，我们期望这些改进的试剂将允许更有效和更少可变的基于投射的靶向具有分子货物的神经元，并促进新型的基于电路的映射实验。

A central goal in neuroscience is to understand behavior in terms of the activity and connectivity of specific neurons. Anatomical tracings have revealed the mesoscale connections in the brain, but this dataset lacks functional utility without the ability to behaviorally study neurons with specific connections to other brain regions. Recently, a number of technological advances have enabled these types of experiments, including re-engineered viruses to target specific neuron types and deliver genes of interests. This methodology is important because genetic targeting of specific neurons allows one to draw a link between a neurons's anatomy (the regions it projects to) and its function (the information it encodes). This project will explore the engineering of novel tools that will significantly improve existing retrograde tracing techniques and thereby enable mapping behavioral functions to specific neuron types. The resulting tools will be made broadly available to the community to increase their impact and utility.As systems neuroscience is adopting tools from molecular biology there is an increasing appreciation for the importance of circuit-specific technologies, for instance targeting neuron-types defined by their projections using retrograde viral strategies for anatomical and genetic labeling. These tools have been critical for cell-type specific recordings using genetic activity indicators, or control using optogenetic actuators. Nevertheless, the efficiency and variable tropism (i.e. inability to target all cell types) of existing retrograde viruses presents a challenge for these experimental approaches. To overcome this challenge, two methods are proposed to generate reagents that will provide a non-toxic profile while maximizing efficient labeling of the targeted population. The methods will exploit well-understood molecular mechanisms for viral internalization to overcome tropisms, as well as classic tracers improved using a novel protein ligation technique. These reagents will be suitable for precise and robust anatomical tracing, for induction of opto- and chemicogenetic actuators. Therefore we expect that these improved reagents will allow for more efficient and less variable projection-based targeting of neurons with molecular cargo and facilitate new types of circuit-based mapping experiments.