Curated Optogenetic Publication Database

Abstract: The SpyCatcher/SpyTag protein conjugation system has recently exploded in popularity due to its fast kinetics and high yield under biologically favorable conditions in both in vitro and intracellular settings. The utility of this system could be expanded by introducing the ability to spatially and temporally control the conjugation event. Taking inspiration from photoreceptor proteins in nature, we designed a method to integrate light dependency into the protein conjugation reaction. The light-oxygen-voltage domain 2 of Avena sativa (AsLOV2) undergoes a dramatic conformational change in its c-terminal Jα-helix in response to blue light. By inserting SpyTag into the different locations of the Jα-helix, we created a blue light inducible SpyTag system (BLISS). In this design, the SpyTag is blocked from reacting with the SpyCatcher in the dark, but upon irradiation with blue light, the Jα-helix of the AsLOV2 undocks to expose the SpyTag. We tested several insertion sites and characterized the kinetics. We found three variants with dynamic ranges over 15, which were active within different concentration ranges. These could be tuned using SpyCatcher variants with different reaction kinetics. Further, the reaction could be instantaneously quenched by removing light. We demonstrated the spatial aspect of this light control mechanism through photopatterning of two fluorescent proteins. This system offers opportunities for many other biofabrication and optogenetics applications.

Abstract: The shuttling of transcription factors and transcriptional regulators into and out of the nucleus is central to the regulation of many biological processes. Here we describe a new method for studying the rates of nuclear entry and exit of transcriptional regulators. A photo-responsive AsLOV (Avena sativa Light Oxygen Voltage) domain is used to sequester fluorescently-labelled transcriptional regulators YAP1 and TAZ/WWTR1 on the surface of mitochondria and reversibly release them upon blue light illumination. After dissociation, fluorescent signals from mitochondria, cytoplasm and nucleus are extracted with a bespoke app and used to generate rates of nuclear entry and exit. Using this method, we demonstrate that phosphorylation of YAP1 on canonical sites enhances its rate of nuclear export. Moreover, we provide evidence that, despite high intercellular variability, YAP1 import and export rates correlated within the same cell. By simultaneously releasing YAP1 and TAZ from sequestration, we show that their rates of entry and exit are correlated. Furthermore, combining the optogenetic release of YAP1 with lattice light-sheet microscopy revealed high heterogeneity of YAP1 dynamics within different cytoplasmic regions, demonstrating the utility and versatility of our tool to study protein dynamics.

Abstract: Using the optogenetic photo-manipulation of photoactivatable (PA)-Rac1, remarkable cell surface ruffling and the formation of a macropinocytic cup (premacropinosome) could be induced in the region of RAW264 macrophages irradiated with blue light due to the activation of PA-Rac1. However, the completion of macropinosome formation did not occur until Rac1 was deactivated by the removal of the light stimulus. Following PA-Rac1 deactivation, some premacropinosomes closed into intracellular macropinosomes, whereas many others transformed into long Rab10-positive tubules without forming typical macropinosomes. These Rab10-positive tubules moved centripetally towards the perinuclear Golgi region along microtubules. Surprisingly, these Rab10-positive tubules did not contain any endosome/lysosome compartment markers, such as Rab5, Rab7, or LAMP1, suggesting that the Rab10-positive tubules were not part of the degradation pathway for lysosomes. These Rab10-positive tubules were distinct from recycling endosomal compartments, which are labeled with Rab4, Rab11, or SNX1. These findings suggested that these Rab10-positive tubules may be a part of non-degradative endocytic pathway that has never been known. The formation of Rab10-positive tubules from premacropinosomes was also observed in control and phorbol myristate acetate (PMA)-stimulated macrophages, although their frequencies were low. Interestingly, the formation of Rab10-positive premacropinosomes and tubules was not inhibited by phosphoinositide 3-kinase (PI3K) inhibitors, while the classical macropinosome formation requires PI3K activity. Thus, this study provides evidence to support the existence of Rab10-positive tubules as a novel endocytic pathway that diverges from canonical macropinocytosis.

Abstract: Development of regulated cellular processes and signaling methods in synthetic cells is essential for their integration with living materials. Light is an attractive tool to achieve this, but the limited penetration depth into tissue of visible light restricts its usability for in-vivo applications. Here, we describe the synthesis and application of blue-light-generating synthetic cells using bioluminescence, dismissing the need for an external light source. First, the lipid membrane and internal composition of light-producing synthetic cells were optimized to enable high-intensity emission. Next, we show these cells’ capacity for triggering bioprocesses in natural cells by initiating asexual sporulation of dark-grown mycelial cells of the fungus Trichoderma atroviride in a quorum-sensing like mechanism. Finally, we demonstrate regulated transcription and membrane recruitment in synthetic cells using bioluminescent self-activating fusion proteins. These functionalities pave the way for deploying synthetic cells as embeddable microscale light sources that are capable of activating engineered processes inside tissues.

Abstract: Materials in nature have fascinating properties that serve as a continuous source of inspiration for materials scientists. Accordingly, bio-mimetic and bio-inspired approaches have yielded remarkable structural and functional materials for a plethora of applications. Despite these advances, many properties of natural materials remain challenging or yet impossible to incorporate into synthetic materials. Natural materials are produced by living cells, which sense and process environmental cues and conditions by means of signaling and genetic programs, thereby controlling the biosynthesis, remodeling, functionalization, or degradation of the natural material. In this context, synthetic biology offers unique opportunities in materials sciences by providing direct access to the rational engineering of how a cell senses and processes environmental information and translates them into the properties and functions of materials. Here, we identify and review two main directions by which synthetic biology can be harnessed to provide new impulses for the biologization of the materials sciences: first, the engineering of cells to produce precursors for the subsequent synthesis of materials. This includes materials that are otherwise produced from petrochemical resources, but also materials where the bio-produced substances contribute unique properties and functions not existing in traditional materials. Second, engineered living materials that are formed or assembled by cells or in which cells contribute specific functions while remaining an integral part of the living composite material. We finally provide a perspective of future scientific directions of this promising area of research and discuss science policy that would be required to support research and development in this field.

Abstract: For various research questions in metabolism, it is highly desirable to have means available, with which the flux through specific pathways can be perturbed dynamically, in a reversible manner, and at a timescale that is consistent with the fast turnover rates of metabolism. Optogenetics, in principle, offers such possibility. Here, we developed an initial version of a photo-switchable isocitrate dehydrogenase (IDH) aimed at controlling the metabolic flux through the citric acid cycle in budding yeast. By inserting a protein-based light switch (LOV2) into computationally identified active/regulatory-coupled sites of IDH and by using in vivo screening in Saccharomyces cerevisiae, we obtained a number of IDH enzymes whose activity can be switched by light. Subsequent in-vivo characterization and optimization resulted in an initial version of photo-switchable (PS) IDH. While further improvements of the enzyme are necessary, our study demonstrates the efficacy of the overall approach from computational design, via in vivo screening and characterization. It also represents one of the first few examples, where optogenetics were used to control the activity of a metabolic enzyme.

Abstract: Fibrodysplasia ossificans progressiva (FOP) and diffuse intrinsic pontine glioma (DIPG) are debilitating diseases that share causal mutations in ACVR1, a TGF-β family type I receptor. ACVR1R206H is a frequent mutation in both diseases. Pathogenic signaling via the SMAD1/5 pathway is mediated by Activin A, but how the mutation triggers aberrant signaling is not known. We show that ACVR1 is essential for Activin A-mediated SMAD1/5 phosphorylation and is activated by two distinct mechanisms. Wild-type ACVR1 is activated by the Activin type I receptors, ACVR1B/C. In contrast, ACVR1R206H activation does not require upstream kinases, but is predominantly activated via Activin A-dependent receptor clustering, which induces its auto-activation. We use optogenetics and live-imaging approaches to demonstrate Activin A-induced receptor clustering and show it requires the type II receptors ACVR2A/B. Our data provide molecular mechanistic insight into the pathogenesis of FOP and DIPG by linking the causal activating genetic mutation to disrupted signaling.

Abstract: Biological signals are sensed by their respective receptors and are transduced and processed by a sophisticated intracellular signaling network leading to a signal-specific cellular response. Thereby, the response to the signal depends on the strength, the frequency, and the duration of the stimulus as well as on the subcellular signal progression. Optogenetic tools are based on genetically encoded light-sensing proteins facilitating the precise spatiotemporal control of signal transduction pathways and cell fate decisions in the absence of natural ligands. In this review, we provide an overview of optogenetic approaches connecting light-regulated protein-protein interaction or caging/uncaging events with steering the function of signaling proteins. We briefly discuss the most common optogenetic switches and their mode of action. The main part deals with the engineering and application of optogenetic tools for the control of transmembrane receptors including receptor tyrosine kinases, the T cell receptor and integrins, and their effector proteins. We also address the hallmarks of optogenetics, the spatial and temporal control of signaling events.

Abstract: Here we describe the development and characterization of the photo-N-degron, a peptide tag that can be used in optogenetic studies of protein function in vivo. The photo-N-degron can be expressed as a genetic fusion to the amino termini of other proteins, where it undergoes a blue light-dependent conformational change that exposes a signal for the class of ubiquitin ligases, the N-recognins, which mediate the N-end rule mechanism of proteasomal degradation. We demonstrate that the photo-N-degron can be used to direct light-mediated degradation of proteins in Saccharomyces cerevisiae and Drosophila melanogaster with fine temporal control. In addition, we compare the effectiveness of the photo-N-degron with that of two other light-dependent degrons that have been developed in their abilities to mediate the loss of function of Cactus, a component of the dorsal-ventral patterning system in the Drosophila embryo. We find that like the photo-N-degron, the blue light-inducible degradation (B-LID) domain, a light-activated degron that must be placed at the carboxy terminus of targeted proteins, is also effective in eliciting light-dependent loss of Cactus function, as determined by embryonic dorsal-ventral patterning phenotypes. In contrast, another previously described photosensitive degron (psd), which also must be located at the carboxy terminus of associated proteins, has little effect on Cactus-dependent phenotypes in response to illumination of developing embryos. These and other observations indicate that care must be taken in the selection and application of light-dependent and other inducible degrons for use in studies of protein function in vivo, but importantly demonstrate that N- and C-terminal fusions to the photo-N-degron and the B-LID domain, respectively, support light-dependent degradation in vivo.

Abstract: Herein, a set of optogenetic tools (designated LiPOP) that enable photoswitchable necroptosis and pyroptosis in live cells with varying kinetics, is introduced. The LiPOP tools allow reconstruction of the key molecular steps involved in these two non-apoptotic cell death pathways by harnessing the power of light. Further, the use of LiPOPs coupled with upconversion nanoparticles or bioluminescence is demonstrated to achieve wireless optogenetic or chemo-optogenetic killing of cancer cells in multiple mouse tumor models. LiPOPs can trigger necroptotic and pyroptotic cell death in cultured prokaryotic or eukaryotic cells and in living animals, and set the stage for studying the role of non-apoptotic cell death pathways during microbial infection and anti-tumor immunity.

Abstract: Plant-based photosensors, such as the light-oxygen-voltage sensing domain 2 (LOV2) from oat phototropin 1, can be modularly wired into cell signaling networks to remotely control protein activity and physiological processes. However, the applicability of LOV2 is hampered by the limited choice of available caging surfaces and its preference to accommodate the effector domains downstream of the C-terminal Jα helix. Here, we engineered a set of LOV2 circular permutants (cpLOV2) with additional caging capabilities, thereby expanding the repertoire of genetically encoded photoswitches to accelerate the design of optogenetic devices. We demonstrate the use of cpLOV2-based optogenetic tools to reversibly gate ion channels, antagonize CRISPR-Cas9-mediated genome engineering, control protein subcellular localization, reprogram transcriptional outputs, elicit cell suicide and generate photoactivatable chimeric antigen receptor T cells for inducible tumor cell killing. Our approach is widely applicable for engineering other photoreceptors to meet the growing need of optogenetic tools tailored for biomedical and biotechnological applications.

Abstract: Sprouting angiogenesis is fundamental for development and contributes to cancer, diabetic retinopathy, and cardiovascular diseases. Sprouting angiogenesis depends on the invasive properties of endothelial tip cells. However, there is very limited knowledge on how tip cells invade into tissues. Here, we show that endothelial tip cells use dactylopodia as the main cellular protrusion for invasion into nonvascular extracellular matrix. We show that dactylopodia and filopodia protrusions are balanced by myosin IIA (NMIIA) and actin-related protein 2/3 (Arp2/3) activity. Endothelial cell-autonomous ablation of NMIIA promotes excessive dactylopodia formation in detriment of filopodia. Conversely, endothelial cell-autonomous ablation of Arp2/3 prevents dactylopodia development and leads to excessive filopodia formation. We further show that NMIIA inhibits Rac1-dependent activation of Arp2/3 by regulating the maturation state of focal adhesions. Our discoveries establish a comprehensive model of how endothelial tip cells regulate its protrusive activity and will pave the way toward strategies to block invasive tip cells during sprouting angiogenesis.

Abstract: T cells discriminate between healthy and infected cells with remarkable sensitivity when mounting an immune response, which is hypothesized to depend on T cells combining stimuli from multiple antigen-presenting cell interactions into a more potent response. To quantify the capacity for T cells to accomplish this, we have developed an antigen receptor that is optically tunable within cell conjugates, providing control over the duration, and intensity of intracellular T-cell signaling. We observe limited persistence within the T-cell intracellular network on disruption of receptor input, with signals dissipating entirely in ~15 min, and directly show sustained proximal receptor signaling is required to maintain gene transcription. T cells thus primarily accumulate the outputs of gene expression rather than integrate discrete intracellular signals. Engineering optical control in a clinically relevant chimeric antigen receptor (CAR), we show that this limited signal persistence can be exploited to increase CAR-T cell activation threefold using pulsatile stimulation. Our results are likely to apply more generally to the signaling dynamics of other cellular networks.

Abstract: Abstract not available.

Abstract: Many canonical signaling pathways exhibit complex time-varying responses, yet how minutes-timescale pulses of signaling interact with the dynamics of transcription and gene expression remains poorly understood. Erk-induced immediate early gene (IEG) expression is a model of this interface, exemplifying both dynamic pathway activity and a rapid, potent transcriptional response. Here, we quantitatively characterize IEG expression downstream of dynamic Erk stimuli in individual cells. We find that IEG expression responds rapidly to acute changes in Erk activity, but only in a sub-population of stimulus-responsive cells. We find that while Erk activity partially predicts IEG expression, a majority of response heterogeneity is independent of Erk and can be rapidly tuned by different mitogenic stimuli and parallel signaling pathways. We extend our findings to an in vivo context, the mouse epidermis, where we observe heterogenous immediate-early gene accumulation in both fixed tissue and single-cell RNA-sequencing data. Our results demonstrate that signaling dynamics can be faithfully transmitted to gene expression and suggest that the signaling-responsive population is an important parameter for interpreting gene expression responses.

Abstract: The L-arabinose-responsive AraC and its cognate PBAD promoter underlie one of the most often used chemically inducible prokaryotic gene expression systems in microbiology and synthetic biology. Here, we change the sensing capability of AraC from L-arabinose to blue light, making its dimerization and the resulting PBAD activation light-inducible. We engineer an entire family of blue light-inducible AraC dimers in Escherichia coli (BLADE) to control gene expression in space and time. We show that BLADE can be used with pre-existing L-arabinose-responsive plasmids and strains, enabling optogenetic experiments without the need to clone. Furthermore, we apply BLADE to control, with light, the catabolism of L-arabinose, thus externally steering bacterial growth with a simple transformation step. Our work establishes BLADE as a highly practical and effective optogenetic tool with plug-and-play functionality-features that we hope will accelerate the broader adoption of optogenetics and the realization of its vast potential in microbiology, synthetic biology and biotechnology.

Abstract: Compartmentation of proteins into biomolecular condensates or membraneless organelles formed by phase separation is an emerging principle for the regulation of cellular processes. Creating synthetic condensates that accommodate specific intracellular proteins on demand would have various applications in chemical biology, cell engineering, and synthetic biology. Here, we report the construction of synthetic protein condensates capable of recruiting and/or releasing proteins of interest in living mammalian cells in response to a small molecule or light. By a modular combination of a tandem fusion of two oligomeric proteins, which forms phase-separated synthetic protein condensates in cells, with a chemically induced dimerization tool, we first created a chemogenetic protein condensate system that can rapidly recruit target proteins from the cytoplasm to the condensates by addition of a small-molecule dimerizer. We next coupled the protein-recruiting condensate system with an engineered proximity-dependent protease, which gave a second protein condensate system wherein target proteins previously expressed inside the condensates are released into the cytoplasm by small-molecule-triggered protease recruitment. Furthermore, an optogenetic condensate system that allows reversible release and sequestration of protein activity in a repeatable manner using light was constructed successfully. These condensate systems were applicable to control protein activity and cellular processes such as membrane ruffling and ERK signaling in a time scale of minutes. This proof-of-principle work provides a new platform for chemogenetic and optogenetic control of protein activity in mammalian cells and represents a step toward tailor-made engineering of synthetic protein condensate-based soft materials with various functionalities for biological and biomedical applications.

Abstract: Optogenetics has been harnessed to shed new mechanistic light on current and future therapeutic strategies. This has been to date achieved by the regulation of ion flow and electrical signals in neuronal cells and neural circuits that are known to be affected by disease. In contrast, the optogenetic delivery of trophic biochemical signals, which support cell survival and are implicated in degenerative disorders, has never been demonstrated in an animal model of disease. Here, we reengineered the human and Drosophila melanogaster REarranged during Transfection (hRET and dRET) receptors to be activated by light, creating one-component optogenetic tools termed Opto-hRET and Opto-dRET. Upon blue light stimulation, these receptors robustly induced the MAPK/ERK proliferative signaling pathway in cultured cells. In PINK1B9 flies that exhibit loss of PTEN-induced putative kinase 1 (PINK1), a kinase associated with familial Parkinson's disease (PD), light activation of Opto-dRET suppressed mitochondrial defects, tissue degeneration and behavioral deficits. In human cells with PINK1 loss-of-function, mitochondrial fragmentation was rescued using Opto-dRET via the PI3K/NF-кB pathway. Our results demonstrate that a light-activated receptor can ameliorate disease hallmarks in a genetic model of PD. The optogenetic delivery of trophic signals is cell type-specific and reversible and thus has the potential to inspire novel strategies towards a spatio-temporal regulation of tissue repair.

Abstract: Membrane protrusions that occur on the dorsal surface of a cell are an excellent experimental system to study actin machinery at work in a living cell. Small GTPase Rac1 controls the membrane protrusions that form and encapsulate extracellular volumes to perform pinocytic or phagocytic functions.

Abstract: Optogenetic protein dimerization systems are powerful tools to investigate the biochemical networks that cells use to make decisions and coordinate their activities. These tools, including the improved Light-Inducible Dimer (iLID) system, offer the ability to selectively recruit components to subcellular locations, such as micron-scale regions of the plasma membrane. In this way, the role of individual proteins within signaling networks can be examined with high spatiotemporal resolution. Currently, consistent recruitment is limited by heterogeneous optogenetic component expression, and spatial precision is diminished by protein diffusion, especially over long time scales. Here, we address these challenges within the iLID system with alternative membrane anchoring domains and fusion configurations. Using live cell imaging and mathematical modeling, we demonstrate that the anchoring strategy affects both component expression and diffusion, which in turn impact recruitment strength, kinetics, and spatial dynamics. Compared to the commonly used C-terminal iLID fusion, fusion proteins with large N-terminal anchors show stronger local recruitment, slower diffusion of recruited components, efficient recruitment over wider gene expression ranges, and improved spatial control over signaling outputs. We also define guidelines for component expression regimes for optimal recruitment for both cell-wide and subcellular recruitment strategies. Our findings highlight key sources of imprecision within light-inducible dimer systems and provide tools that allow greater control of subcellular protein localization across diverse cell biological applications.

Abstract: Dynamic control of microbial metabolism is an effective strategy to improve chemical production in fermentations. While dynamic control is most often implemented using chemical inducers, optogenetics offers an attractive alternative due to the high tunability and reversibility afforded by light. However, a major concern of applying optogenetics in metabolic engineering is the risk of insufficient light penetration at high cell densities, especially in large bioreactors. Here, we present a new series of optogenetic circuits we call OptoAMP, which amplify the transcriptional response to blue light by as much as 23-fold compared to the basal circuit (OptoEXP). These circuits show as much as a 41-fold induction between dark and light conditions, efficient activation at light duty cycles as low as ∼1%, and strong homogeneous light-induction in bioreactors of at least 5 L, with limited illumination at cell densities above 40 OD600. We demonstrate the ability of OptoAMP circuits to control engineered metabolic pathways in novel three-phase fermentations using different light schedules to control enzyme expression and improve production of lactic acid, isobutanol, and naringenin. These circuits expand the applicability of optogenetics to metabolic engineering.

Abstract: Ulcerative colitis (UC) is a relapsing disorder characterized by chronic inflammation of the intestinal tract. However, the home care of UC based on remote monitoring, due to the operational complexity and time-consuming procedure, restrain its widespread applications. Here we constructed an optotheranostic nanosystem for self-diagnosis and long-acting mitigations of UC at home. The system included two major modules: (i) A disease prescreening module mediated by smartphone optical sensing. (ii) Disease real-time intervention module mediated by an optogenetic engineered bacteria system. Recombinant Escherichia coli Nissle 1917 (EcN) secreted interleukin-10 (IL-10) could downregulate inflammatory cascades and matrix metalloproteinases; it is a candidate for use in the therapeutic intervention of UC. The results showed that the Detector was able to analyze, report, and share the detection results in less than 1 min, and the limit of detection was 15 ng·mL-1. Besides, the IL-10-secreting EcN treatment suppressed the intestinal inflammatory response in UC mice and protected the intestinal mucosa against injury. The optotheranostic nanosystems enabled solutions to diagnose and treat disease at home, which promotes a mobile health service development.

Abstract: Molecular brain therapies require the development of molecular switches to control gene expression in a limited and regulated manner in time and space. Light-switchable gene systems allow precise control of gene expression with an enhanced spatio-temporal resolution compared to chemical inducers. In this work, we adapted the existing light-switchable Light-On system into a lentiviral platform, which consists of two modules: (i) one for the expression of the blue light-switchable trans-activator GAVPO and (ii) a second module containing an inducible-UAS promoter (UAS) modulated by a light-activated GAVPO.

Abstract: The phototropins (phots) are light-activated kinases that are critical for plant physiology and the many diverse optogenetic tools that they have inspired. Phototropins combine two blue light sensing Light-Oxygen-Voltage (LOV) domains (LOV1 and LOV2) and a C-terminal serine/threonine kinase domain, using the LOV domains to control the catalytic activity of the kinase. While much is known about the structure and photochemistry of the light-perceiving LOV domains, particularly in how activation of the LOV2 domain triggers the unfolding of alpha helices that communicate the light signal to the kinase domain, many questions about phot structure and mechanism remain. Recent studies have made progress addressing these questions by utilizing small angle X-ray scattering (SAXS) and other biophysical approaches to study multidomain phots from Chlamydomonas and Arabidopsis, leading to models where the domains have an extended linear arrangement, with the activating LOV2 domain contacting the kinase domain N-lobe. We discuss this and other advances which have improved structural and mechanistic understanding of phot regulation in this review, along with the challenges that will have to be overcome to obtain high-resolution structural information on these exciting photoreceptors. Such information will be essential to advancing fundamental understanding of plant physiology while enabling engineering efforts at both the whole plant and molecular levels.

Abstract: Voltage-gated potassium (Kv) channels regulate the membrane potential and conductance of excitable cells to control the firing rate and waveform of action potentials. Even though Kv channels have been intensely studied for over 70 year, surprisingly little is known about how specific channels expressed in various neurons and their functional properties impact neuronal network activity and behavior in vivo. Although many in vivo genetic manipulations of ion channels have been tried, interpretation of these results is complicated by powerful homeostatic plasticity mechanisms that act to maintain function following perturbations in excitability. To better understand how Kv channels shape network function and behavior, we have developed a novel optogenetic technology to acutely regulate Kv channel expression with light by fusing the light-sensitive LOV domain of Vaucheria frigida Aureochrome 1 to the N-terminus of the Kv1 subunit protein to make an Opto-Kv1 channel. Recording of Opto-Kv1 channels expressed in Xenopus oocytes, mammalian cells, and neurons show that blue light strongly induces the current expression of Opto-Kv1 channels in all systems tested. We also find that an Opto-Kv1 construct containing a dominant-negative pore mutation (Opto-Kv1(V400D)) can be used to down-regulate Kv1 currents in a blue light-dependent manner. Finally, to determine whether Opto-Kv1 channels can elicit light-dependent behavioral effect in vivo, we targeted Opto-Kv1 (V400D) expression to Kv1.3-expressing mitral cells of the olfactory bulb in mice. Exposure of the bulb to blue light for 2-3 hours produced a significant increase in sensitivity to novel odors after initial habituation to a similar odor, comparable to behavioral changes seen in Kv1.3 knockout animals. In summary, we have developed novel photoactivatable Kv channels that provide new ways to interrogate neural circuits in vivo and to examine the roles of normal and disease-causing mutant Kv channels in brain function and behavior.