Strategies for optogenetic stimulation of deep tissue peripheral nerves

Abstract

Optogenetic technologies have been the subject of great excitement within the scientific community for their ability to demystify complex neurophysiological pathways in the central and peripheral nervous systems. Optogenetics refers to the transduction of mammalian cells with a light-sensitive transmembrane protein, called an opsin, such that illumination of the target tissue initiates depolarization; in the case of a neuron, illumination results in the firing of an action potential that can control downstream physiology. The excitement surrounding optogenetics has also extended to the clinic with a human trial using the opsin ChR2 in the treatment of retinitis pigmentosa currently underway and several more trials potentially planned for the near future. In this thesis, we focus on the use of viral techniques to transduce peripheral nerve tissue to be responsive to light. We characterize the properties of optogenetic peripheral nerve transduction, optimizing for variables such as expression strength, wavelength specificity, and time-course of expression. Within the scope of this thesis, three new methods for optogenetic peripheral nerve stimulation are described: (1) a method for optogenetic motor nerve control using transdermal illumination, (2) a method employing unique wavelengths to selectively target optogenetic subsets of motor nerves, and (3) a method for extending optogenetic expression strength and timecourse. The work is important because it lays the foundation for future advancements in optogenetic peripheral nerve stimulation in both a scientific and clinical context.