Optogenetics in Neural Systems Yizhar, Ofer; Fenno, Lief E.; Davidson, Thomas J. ...
Neuron (Cambridge, Mass.),
07/2011, Letnik:
71, Številka:
1
Journal Article
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Both observational and perturbational technologies are essential for advancing the understanding of brain function and dysfunction. But while observational techniques have greatly advanced in the ...last century, techniques for perturbation that are matched to the speed and heterogeneity of neural systems have lagged behind. The technology of optogenetics represents a step toward addressing this disparity. Reliable and targetable single-component tools (which encompass both light sensation and effector function within a single protein) have enabled versatile new classes of investigation in the study of neural systems. Here we provide a primer on the application of optogenetics in neuroscience, focusing on the single-component tools and highlighting important problems, challenges, and technical considerations.
Social interaction is a complex behavior essential for many species and is impaired in major neuropsychiatric disorders. Pharmacological studies have implicated certain neurotransmitter systems in ...social behavior, but circuit-level understanding of endogenous neural activity during social interaction is lacking. We therefore developed and applied a new methodology, termed fiber photometry, to optically record natural neural activity in genetically and connectivity-defined projections to elucidate the real-time role of specified pathways in mammalian behavior. Fiber photometry revealed that activity dynamics of a ventral tegmental area (VTA)-to-nucleus accumbens (NAc) projection could encode and predict key features of social, but not novel object, interaction. Consistent with this observation, optogenetic control of cells specifically contributing to this projection was sufficient to modulate social behavior, which was mediated by type 1 dopamine receptor signaling downstream in the NAc. Direct observation of deep projection-specific activity in this way captures a fundamental and previously inaccessible dimension of mammalian circuit dynamics.
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•Fiber photometry enables recording of neural projection activity in behaving mice•VTA-NAc projection activity encodes and predicts social interaction•Optogenetic control of VTA DA neurons bidirectionally modulates social behavior•Elevating VTA-NAc activity and NAc D1R signaling increases social behavior
A new method called fiber photometry allows recording of the natural neuronal activity of neuronal projections in behaving mice. Such recordings in mice partaking in social interactions reveal that the dynamics of a neural projection between the ventral tegmental area (VTA) and nucleus accumbens (NAc) encode and predict key features of social behavior.
Water deprivation produces a drive to seek and consume water. How neural activity creates this motivation remains poorly understood. We used activity-dependent genetic labeling to characterize ...neurons activated by water deprivation in the hypothalamic median preoptic nucleus (MnPO). Single-cell transcriptional profiling revealed that dehydration-activated MnPO neurons consist of a single excitatory cell type. After optogenetic activation of these neurons, mice drank water and performed an operant lever-pressing task for water reward with rates that scaled with stimulation frequency. This stimulation was aversive, and instrumentally pausing stimulation could reinforce lever-pressing. Activity of these neurons gradually decreased over the course of an operant session. Thus, the activity of dehydration-activated MnPO neurons establishes a scalable, persistent, and aversive internal state that dynamically controls thirst-motivated behavior.
In vivo experimental evidence indicates that acute neuronal activation increases Aβ release from presynaptic terminals, whereas long-term effects of chronic synaptic activation on Aβ pathology remain ...unclear. To address this issue, we adopted optogenetics and transduced stabilized step-function opsin, a channelrhodopsin engineered to elicit a long-lasting neuronal hyperexcitability, into the hippocampal perforant pathway of APP transgenic mice. In vivo microdialysis revealed a ∼24% increase in the hippocampal interstitial fluid Aβ42 levels immediately after acute light activation. Five months of chronic optogenetic stimulation increased Aβ burden specifically in the projection area of the perforant pathway (i.e., outer molecular layer of the dentate gyrus) of the stimulated side by ∼2.5-fold compared with that in the contralateral side. Epileptic seizures were observed during the course of chronic stimulation, which might have partly contributed to the Aβ pathology. These findings implicate functional abnormalities of specific neuronal circuitry in Aβ pathology and Alzheimer disease.
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•Perforant pathway is chronically activated with stabilized step-function opsin•Acute optogenetic activation increases the interstitial fluid Aβ42 level•Five months of chronic activation increases Aβ deposition in the projection area
Neuronal or synaptic activity has been implicated in the pathogenesis of Alzheimer disease. Yamamoto et al. show that chronic activation of the hippocampal perforant pathway in APP transgenic mice, using optogenetics, augments Aβ pathology within the presynaptic projection area in the dentate gyrus of the hippocampus.
Severe behavioural deficits in psychiatric diseases such as autism and schizophrenia have been hypothesized to arise from elevations in the cellular balance of excitation and inhibition (E/I balance) ...within neural microcircuitry. This hypothesis could unify diverse streams of pathophysiological and genetic evidence, but has not been susceptible to direct testing. Here we design and use several novel optogenetic tools to causally investigate the cellular E/I balance hypothesis in freely moving mammals, and explore the associated circuit physiology. Elevation, but not reduction, of cellular E/I balance within the mouse medial prefrontal cortex was found to elicit a profound impairment in cellular information processing, associated with specific behavioural impairments and increased high-frequency power in the 30-80 Hz range, which have both been observed in clinical conditions in humans. Consistent with the E/I balance hypothesis, compensatory elevation of inhibitory cell excitability partially rescued social deficits caused by E/I balance elevation. These results provide support for the elevated cellular E/I balance hypothesis of severe neuropsychiatric disease-related symptoms.
The resolution and dimensionality with which biologists can characterize cell types have expanded dramatically in recent years, and intersectional consideration of such features (e.g., multiple gene ...expression and anatomical parameters) is increasingly understood to be essential. At the same time, genetically targeted technology for writing in and reading out activity patterns for cells in living organisms has enabled causal investigation in physiology and behavior; however, cell-type-specific delivery of these tools (including microbial opsins for optogenetics and genetically encoded Ca2+ indicators) has thus far fallen short of versatile targeting to cells jointly defined by many individually selected features. Here, we develop a comprehensive intersectional targeting toolbox including 39 novel vectors for joint-feature-targeted delivery of 13 molecular payloads (including opsins, indicators, and fluorophores), systematic approaches for development and optimization of new intersectional tools, hardware for in vivo monitoring of expression dynamics, and the first versatile single-virus tools (Triplesect) that enable targeting of triply defined cell types.
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•Multiple recombinase-dependent expression of 15 new molecular payloads in single AAVs•Intersectional Ca2+ imaging, cell labeling, and optogenetic inhibition or excitation•Creation and in vivo validation of triple-feature-dependent viruses (Triplesect)•Design of a widely adaptable in vivo quantitative expression tracking system
Fenno et al. enable versatile functional access to cell types defined by the presence of multiple (2 or 3) features, creating diverse expression-control logic contained in single viruses. This result is a comprehensive toolset enabling multiple-feature-dependent optogenetic inhibition and excitation and structure- or activity-based fluorescence imaging with diverse new indicators.
The capture and utilization of light is an exquisitely evolved process. The single-component microbial opsins, although more limited than multicomponent cascades in processing, display unparalleled ...compactness and speed. Recent advances in understanding microbial opsins have been driven by molecular engineering for optogenetics and by comparative genomics. Here we provide a Primer on these light-activated ion channels and pumps, describe a group of opsins bridging prior categories, and explore the convergence of molecular engineering and genomic discovery for the utilization and understanding of these remarkable molecular machines.
The lateral hypothalamic area (LHA) regulates feeding- and reward-related behavior, but because of its molecular and anatomical heterogeneity, the functions of defined neuronal populations are ...largely unclear. Glutamatergic neurons within the LHA (LHAVglut2) negatively regulate feeding and appetitive behavior. However, this population comprises transcriptionally distinct and functionally diverse neurons that project to diverse brain regions, including the lateral habenula (LHb) and ventral tegmental area (VTA). To resolve the function of distinct LHAVglut2 populations, we systematically compared projections to the LHb and VTA using viral tracing, single-cell sequencing, electrophysiology, and in vivo calcium imaging. LHAVglut2 neurons projecting to the LHb or VTA are anatomically, transcriptionally, electrophysiologically, and functionally distinct. While both populations encode appetitive and aversive stimuli, LHb projecting neurons are especially sensitive to satiety state and feeding hormones. These data illuminate the functional heterogeneity of LHAVglut2 neurons, suggesting that reward and aversion are differentially processed in divergent efferent pathways.
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•LHA glutamate projections to LHb and VTA are anatomically and molecularly distinct•LHb projectors are more active and excitable than VTA projectors•LHb and VTA projections discern appetitive and aversive tastes and satiety states•Leptin and Ghrelin differentially influence LHb and VTA projection reward encoding
Rossi et al. systematically compare lateral hypothalamic glutamatergic neurons projecting to LHb and VTA using viral tracing, single-cell sequencing, electrophysiology, and in vivo calcium imaging. The two populations are anatomically, transcriptionally, and functionally distinct. In vivo dynamics are modified by stimulus valance, satiety, and the feeding hormones leptin and ghrelin.
The naturally occurring channelrhodopsin variant anion channelrhodopsin-1 (ACR1), discovered in the cryptophyte algae Guillardia theta, exhibits large light-gated anion conductance and high ...anion selectivity when expressed in heterologous settings, properties that support its use as an optogenetic tool to inhibit neuronal firing with light. However, molecular insight into ACR1 is lacking owing to the absence of structural information underlying light-gated anion conductance. Here we present the crystal structure of G. theta ACR1 at 2.9 Å resolution. The structure reveals unusual architectural features that span the extracellular domain, retinal-binding pocket, Schiff-base region, and anion-conduction pathway. Together with electrophysiological and spectroscopic analyses, these findings reveal the fundamental molecular basis of naturally occurring light-gated anion conductance, and provide a framework for designing the next generation of optogenetic tools.
Significance Stroke is the leading cause of disability in the United States and has very limited treatment options. Brain stimulation techniques that promote recovery after stroke are a promising ...area of research; however, current stimulation techniques nonspecifically activate/inhibit the target area, which not only leads to undesired side effects but also makes it difficult to understand which cell types and mechanisms drive recovery. We used the optogenetic technique to specifically stimulate only neurons after stroke and demonstrate that selective neuronal stimulations can activate beneficial mechanisms and promote recovery. Understanding the cell type and mechanisms driving recovery may identify potential drug targets for stroke treatment, as well as ultimately help develop precise brain stimulation techniques for stroke therapy.
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