Multidimensional screening yields channelrhodopsin variants having improved photocurrent and order-of-magnitude reductions in calcium and proton currents.

Channelrhodopsins (ChRs) are light-gated ion channels in widespread use in neuroscience for mediating the genetically targetable optical control of neurons (optogenetics). ChRs pass multiple kinds of ions, and although nonspecific ChR-mediated conductance is not an issue in many neuroscience studies, conductance of calcium and protons, which can mediate diverse cellular signals, may be undesirable in some instances. Here, we turned our attention to the creation of ChRs that have high cation photocurrent but pass fewer calcium ions and protons.

Noninvasive optical inhibition with a red-shifted microbial rhodopsin.

Optogenetic inhibition of the electrical activity of neurons enables the causal assessment of their contributions to brain functions. Red light penetrates deeper into tissue than other visible wavelengths. We present a red-shifted cruxhalorhodopsin, Jaws, derived from Haloarcula (Halobacterium) salinarum (strain Shark) and engineered to result in red light-induced photocurrents three times those of earlier silencers.

Independent optical excitation of distinct neural populations.

Optogenetic tools enable examination of how specific cell types contribute to brain circuit functions. A long-standing question is whether it is possible to independently activate two distinct neural populations in mammalian brain tissue. Such a capability would enable the study of how different synapses or pathways interact to encode information in the brain.

Synthetic physiology strategies for adapting tools from nature for genetically targeted control of fast biological processes.

The life and operation of cells involve many physiological processes that take place over fast timescales of milliseconds to minutes. Genetically encoded technologies for driving or suppressing specific fast physiological processes in intact cells, perhaps embedded within intact tissues in living organisms, are critical for the ability to understand how these physiological processes contribute to emergent cellular and organismal functions and behaviors. Such "synthetic physiology" tools are often incredibly complex molecular machines, in part because they must operate at high speeds, without causing side effects.

High-performance genetically targetable optical neural silencing by light-driven proton pumps.

The ability to silence the activity of genetically specified neurons in a temporally precise fashion would provide the opportunity to investigate the causal role of specific cell classes in neural computations, behaviours and pathologies. Here we show that members of the class of light-driven outward proton pumps can mediate powerful, safe, multiple-colour silencing of neural activity. The gene archaerhodopsin-3 (Arch) from Halorubrum sodomense enables near-100% silencing of neurons in the awake brain when virally expressed in the mouse cortex and illuminated with yellow light.

Informational lesions: optical perturbation of spike timing and neural synchrony via microbial opsin gene fusions.

Synchronous neural activity occurs throughout the brain in association with normal and pathological brain functions. Despite theoretical work exploring how such neural coordination might facilitate neural computation and be corrupted in disease states, it has proven difficult to test experimentally the causal role of synchrony in such phenomena. Attempts to manipulate neural synchrony often alter other features of neural activity such as firing rate.