Wireless Optogenetics by relay nano-illuminators

描述（由申请人提供）：由于光遗传学工具的突破性发展，最近朝着更好地理解神经回路功能迈出了重要的一步。在这种方法中，微生物视蛋白基因[最值得注意的是，通道视紫红质（ChR-2）和盐视紫红质（NpHR）]通过病毒转导或转基因在神经元中表达。表达视蛋白的神经元可以被特定波长的光激活或抑制。由于其巨大的时空分辨率，光遗传学能够从功能上解剖大脑回路，并为大脑之间的因果关系提供新的见解

DESCRIPTION (provided by applicant): An important step toward better understanding neural circuit function was recently made possible thanks to the breakthrough development of optogenetic tools. In this approach, the microbial opsin genes [most notable, Channelrhodopsin (ChR-2) and halorhodopsin (NpHR)] are expressed in neurons either by viral transduction or transgenesis. Neurons expressing opsin can then be activated or inhibited by light at specific wavelengths. Due to its great spatiotemporal resolution, optogenetics is able to functionally dissect brain circuits, as well as to offer new insights into the causal relationship between brain activity and behavior and, possibly, lead to therapies for neuropsychiatric diseases. However, due to the limited tissue penetration of light at the wavelengths necessary to activate optogenetic constructs, the stimulation of behaving animals has to rely on chronically implanted, fiber-optics or mounted LEDs to deliver light into deep brain tissues. Although this method is very useful and has yielded a wealth of information about brain circuits, stimulation via fiber-optics also has important limitations, particularly in regard to chronic stimulation in awake animals. To address this challenging issue, we propose to develop a wireless optogenetic strategy to remotely activate opsins in vivo using a relay nano- illuminator. This approach is buil upon key technologic advances recently made in our laboratory in lanthanide-doped upconversion nanoparticles (UCNPs), a new generation of nanoparticles with unexpected properties. The most significant advantage of UCNPs is their unnatural inverse excitation and emission profiles; i.e., they are excited using biocompatible, low power, deep tissue-penetrant, near infrared radiation that is effectively converted to a higher energy output emission at various shorter wavelengths, including visible light for activation of opsins. We propose two specific aims. For Aim 1, we will characterize the ability of UNCPs to act as "relay illuminators" in vitro and in vivo. We will initially focus on the first generation of UCNP nanoparticles (CaF2 coated core/shell UCNP) that our preliminary experiments have demonstrated to exhibit robust emission from deep brain tissue. In Aim2, we will develop novel combinatorial synthesis to enhance optogenetic performance of lanthanide-doped UCNPs. This new strategy will overcome many of the limitations of current fiber-optic based approaches, and will enable new applications in both fundamental science and human health.