title: Non-invasive activation of optogenetic actuators.
abstract: The manipulation of genetically targeted neurons with light (optogenetics) continues to provide unprecedented avenues into studying the function of the mammalian brain. However, potential translation into the clinical arena faces a number of significant hurdles, foremost among them the need for insertion of optical fibers into the brain to deliver light to opsins expressed on neuronal membranes. In order to overcome these hardware-related problems, we have developed an alternative strategy for delivering light to opsins which does not involve fiber implants. Rather, the light is produced by a protein, luciferase, which oxidizes intravenously applied substrate, thereby emitting bioluminescence. In proof-of-principle studies employing a fusion protein of a light-generating luciferase to a light-sensing opsin (luminopsin), we showed that light emitted byGaussialuciferase is indeed able to activate channelrhodopsin, allowing modulation of neuronal activity when expressed in cultured neurons. Here we assessed applicability of the conceptin vivoin mice expressing luminopsins from viral vectors and from genetically engineered transgenes. The experiments demonstrate that intravenously applied substrate reaches neurons in the brain, causing the luciferase to produce bioluminescence which can be imagedin vivo, and that activation of channelrhodopsin by bioluminescence is sufficient to affect behavior. Further developments of such technology based on combining optogenetics with bioluminescence - i.e. combining light-sensing molecules with biologically produced light through luciferases - should bring optogenetics closer to clinical applications.
authors.affiliation: Neurotransgenic Laboratory, Duke University, Durham, NC, USA.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Birkner
authors.affiliation: Department of Neurobiology, Duke University, Durham, NC, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Berglund
authors.affiliation: Neurotransgenic Laboratory, Duke University, Durham, NC, USA.
authors.forename: Marguerita E
authors.initials: ME
authors.lastname: Klein
authors.affiliation: Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore; Institute of Molecular and Cell Biology, Singapore; Center for Functional Connectomics, Korea Institute of Science and Technology, Seoul, Republic of Korea.
authors.forename: George J
authors.initials: GJ
authors.lastname: Augustine
authors.affiliation: Neurotransgenic Laboratory, Duke University, Durham, NC, USA; Department of Neurobiology, Duke University, Durham, NC, USA.
authors.forename: Ute
authors.initials: U
authors.lastname: Hochgeschwender
keywords: Gaussia luciferase; bioluminescence; channelrhodopsin; coelenterazine; imaging; in vivo; transgenic mice; viral vectors