Curated Optogenetic Publication Database

Abstract: Biological imaging based on light microscopy comes at the core of the methods that let us understanding morphology and its dynamics in synergy to the spatiotemporal distribution of cellular and molecular activities as the organism develops and becomes functional. Non-linear optical tools and superesolution methodologies are under constant development and their applications to live imaging of whole organisms keep improving as we speak. Genetically coded biosensors, multicolor clonal methods and optogenetics in different organisms and, in particular, in Drosophila follow equivalent paths. We anticipate a brilliant future for live imaging providing the roots for the holistic understanding, rather than for individual parts, of development and function at the whole-organism level.

Abstract: Reactive Oxygen Species (ROS) are known to cause oxidative damage to DNA, proteins and lipids. In addition, recent evidence suggests that ROS can also initiate signaling cascades that respond to stress and modify specific redox-sensitive moieties as a regulatory mechanism. This suggests that ROS are physiologically-relevant signaling molecules. However, these sensor/effector molecules are not uniformly distributed throughout the cell. Moreover, localized ROS damage may elicit site-specific compensatory measures. Thus, the impact of ROS can be likened to that of calcium, a ubiquitous second messenger, leading to the prediction that their effects are exquisitely dependent upon their location, quantity and even the timing of generation. Despite this prediction, ROS signaling is most commonly intuited through the global administration of chemicals that produce ROS or by ROS quenching through global application of antioxidants. Optogenetics, which uses light to control the activity of genetically-encoded effector proteins, provides a means of circumventing this limitation. Photo-inducible genetically-encoded ROS-generating proteins (RGPs) were originally employed for their phototoxic effects and cell ablation. However, reducing irradiance and/or fluence can achieve sub-lethal levels of ROS that may mediate subtle signaling effects. Hence, transgenic expression of RGPs as fusions to native proteins gives researchers a new tool to exert spatial and temporal control over ROS production. This review will focus on the new frontier defined by the experimental use of RGPs to study ROS signaling.

Abstract: Low doses of UV-B light (280 to 315 nm) elicit photomorphogenic responses in plants that modify biochemical composition, photosynthetic competence, morphogenesis, and defense. UV RESISTANCE LOCUS8 (UVR8) mediates photomorphogenic responses to UV-B by regulating transcription of a set of target genes. UVR8 differs from other known photoreceptors in that it uses specific Trp amino acids instead of a prosthetic chromophore for light absorption during UV-B photoreception. Absorption of UV-B dissociates the UVR8 dimer into monomers, initiating signal transduction through interaction with CONSTITUTIVELY PHOTOMORPHOGENIC1. However, much remains to be learned about the physiological role of UVR8 and its interaction with other signaling pathways, the molecular mechanism of UVR8 photoreception, how the UVR8 protein initiates signaling, how it is regulated, and how UVR8 regulates transcription of its target genes.

Abstract: The brain is a large network of interconnected neurons where each cell functions as a nonlinear processing element. Unraveling the mysteries of information processing in the complex networks of the brain requires versatile neurostimulation and imaging techniques. Optogenetics is a new stimulation method which allows the activity of neurons to be modulated by light. For this purpose, the cell-types of interest are genetically targeted to produce light-sensitive proteins. Once these proteins are expressed, neural activity can be controlled by exposing the cells to light of appropriate wavelengths. Optogenetics provides a unique combination of features, including multimodal control over neural function and genetic targeting of specific cell-types. Together, these versatile features combine to a powerful experimental approach, suitable for the study of the circuitry of psychiatric and neurological disorders. The advent of optogenetics was followed by extensive research aimed to produce new lines of light-sensitive proteins and to develop new technologies: for example, to control the distribution of light inside the brain tissue or to combine optogenetics with other modalities including electrophysiology, electrocorticography, nonlinear microscopy, and functional magnetic resonance imaging. In this paper, the authors review some of the recent advances in the field of optogenetics and related technologies and provide their vision for the future of the field.

Abstract: Enabling optical control over biological processes is a defining goal of the new field of optogenetics. Control of membrane voltage by natural rhodopsin family ion channels has found widespread acceptance in neuroscience, due to the fact that these natural proteins control membrane voltage without further engineering. In contrast, optical control of intracellular biological processes has been a fragmented effort, with various laboratories engineering light-responsive properties into proteins in different manners. In the present article, we review the various systems that have been developed for controlling protein functions with light based on vertebrate rhodopsins, plant photoregulatory proteins and, most recently, the photoswitchable fluorescent protein Dronpa. By allowing biology to be controlled with spatiotemporal specificity and tunable dynamics, light-controllable proteins will find applications in the understanding of cellular and organismal biology and in synthetic biology.

Abstract: Abstract not available.

Abstract: Ultraviolet-B radiation (UV-B) is an intrinsic part of sunlight that is accompanied by significant biological effects. Plants are able to perceive UV-B using the UV-B photoreceptor UVR8 which is linked to a specific molecular signaling pathway and leads to UV-B acclimation. Herein we review the biological process in plants from initial UV-B perception and signal transduction through to the known UV-B responses that promote survival in sunlight. The UVR8 UV-B photoreceptor exists as a homodimer that instantly monomerises upon UV-B absorption via specific intrinsic tryptophans which act as UV-B chromophores. The UVR8 monomer interacts with COP1, an E3 ubiquitin ligase, initiating a molecular signaling pathway that leads to gene expression changes. This signaling output leads to UVR8-dependent responses including UV-B-induced photomorphogenesis and the accumulation of UV-B-absorbing flavonols. Negative feedback regulation of the pathway is provided by the WD40-repeat proteins RUP1 and RUP2, which facilitate UVR8 redimerization, disrupting the UVR8-COP1 interaction. Despite rapid advancements in the field of recent years, further components of UVR8 UV-B signaling are constantly emerging, and the precise interplay of these and the established players UVR8, COP1, RUP1, RUP2 and HY5 needs to be defined. UVR8 UV-B signaling represents our further understanding of how plants are able to sense their light environment and adjust their growth accordingly.

Abstract: Phytochromes are plant photoreceptors that perceive red and far-red light. Upon the perception of light in Arabidopsis, light-activated phytochromes enter the nucleus and act on a set of interacting proteins, modulating their activities and thereby altering the expression levels of ∼10% of the organism's entire gene complement. Phytochromeinteracting factors (PIFs) belonging to Arabidopsis basic helix-loop-helix (bHLH) subgroup 15 are key interacting proteins that play negative roles in light responses. Their activities are post-translationally countered by light-activated phytochromes, which promote the degradation of PIFs and directly or indirectly inhibit their binding to DNA. The PIFs share a high degree of similarity, but examinations of pif single and multiple mutants have indicated that they have shared and distinct functions in various developmental and physiological processes. These are believed to stem from differences in both intrinsic protein properties and their gene expression patterns. In an effort to clarify the basis of these shared and distinct functions, we compared recently published genome-wide ChIP data, developmental gene expression maps, and responses to various stimuli for the various PIFs. Based on our observations, we propose that the biological roles of PIFs stem from their shared and distinct DNA binding targets and specific gene expression patterns.

Abstract: The development and progress in synthetic biology has been remarkable. Although still in its infancy, synthetic biology has achieved much during the past decade. Improvements in genetic circuit design have increased the potential for clinical applicability of synthetic biology research. What began as simple transcriptional gene switches has rapidly developed into a variety of complex regulatory circuits based on the transcriptional, translational and post-translational regulation. Instead of compounds with potential pharmacologic side effects, the inducer molecules now used are metabolites of the human body and even members of native cell signaling pathways. In this review, we address recent progress in mammalian synthetic biology circuit design and focus on how novel designs push synthetic biology toward clinical implementation. Groundbreaking research on the implementation of optogenetics and intercellular communications is addressed, as particularly optogenetics provides unprecedented opportunities for clinical application. Along with an increase in synthetic network complexity, multicellular systems are now being used to provide a platform for next-generation circuit design.

Abstract: In this issue of Chemistry & Biology, Renicke et al. report a photosensitive degron (psd) consisting of the LOV2 domain fused to a protein degradation sequence. This design enabled light-dependent protein degradation in yeast. When psd was fused to cell-cycle-dependent proteins, it controlled cell cycle by light with spatiotemporal precision.

Abstract: Light is fundamental to life on earth. Therefore, nature has evolved a multitude of photoreceptors that sense light across all kingdoms. This natural resource provides synthetic biology with a vast pool of light-sensing components with distinct spectral properties that can be harnessed to engineer novel optogenetic tools. These devices enable control over gene expression, cell morphology and signaling pathways with superior spatiotemporal resolution and are maturing towards elaborate applications in basic research, in the production of biopharmaceuticals and in biomedicine. This article provides a summary of the recent advances in optogenetics that use light for the precise control of biological functions in mammalian cells.

Abstract: Optogenetics arises from the innovative application of microbial opsins in mammalian neurons and has since been a powerful technology that fuels the advance of our knowledge in neuroscience. In recent years, there has been growing interest in designing optogenetic tools extendable to broader cell types and biochemical signals. To date, a variety of photoactivatable proteins (refers to induction of protein activity in contrast to fluorescence) have been developed based on the understanding of plant and microbial photoreceptors including phototropins, blue light sensors using flavin adenine dinucleotide proteins, cryptochromes, and phytochromes. Such tools offered researchers reversible, quantitative, and precise spatiotemporal control of enzymatic activity, protein-protein interaction, protein translocation, as well as gene transcription in cells and in whole animals. In this review, we will briefly introduce these photosensory proteins, describe recent developments in optogenetics, and compare and contrast different methods based on their advantages and limitations.

Abstract: Near-infrared light is favourable for imaging in mammalian tissues due to low absorbance of hemoglobin, melanin, and water. Therefore, fluorescent proteins, biosensors and optogenetic constructs for optimal imaging, optical readout and light manipulation in mammals should have fluorescence and action spectra within the near-infrared window. Interestingly, natural Bacterial Phytochrome Photoreceptors (BphPs) utilize the low molecular weight biliverdin, found in most mammalian tissues, as a photoreactive chromophore. Due to their near-infrared absorbance BphPs are preferred templates for designing optical molecular tools for applications in mammals. Moreover, BphPs spectrally complement existing genetically-encoded probes. Several BphPs were already developed into the near-infrared fluorescent variants. Based on the analysis of the photochemistry and structure of BphPs we suggest a variety of possible BphP-based fluorescent proteins, biosensors, and optogenetic tools. Putative design strategies and experimental considerations for such probes are discussed.

Abstract: Over the past decades, there has been growing recognition that light can provide a powerful stimulus for biological interrogation. Light-actuated tools allow manipulation of molecular events with ultra-fine spatial and fast temporal resolution, as light can be rapidly delivered and focused with sub-micrometre precision within cells. While light-actuated chemicals such as photolabile 'caged' compounds have been in existence for decades, the use of genetically encoded natural photoreceptors for optical control of biological processes has recently emerged as a powerful new approach with several advantages over traditional methods. Here, we review recent advances using light to control basic cellular functions and discuss the engineering challenges that lie ahead for improving and expanding the ever-growing optogenetic toolkit.

Abstract: BLUF (sensor of blue light using FAD) domain-containing proteins are one of three types of flavin-binding, blue-light-sensing proteins found in many bacteria and some algae. The other types of blue-light-sensing proteins are the cryptochromes and the light, oxygen, voltage (LOV) domain-containing proteins. BLUF proteins control a wide variety of light-dependent physiological activities including photosystem synthesis, biofilm formation and the photoavoidance response. The BLUF domain photochemical reaction is unique in that only small chromophore structural changes are involved in the light activation process, because the rigid flavin moiety is involved, rather than an isomerizable chromophore (e.g. phytochromobilin in phytochromes and retinal in rhodopsins). Recent spectroscopic, biochemical and structural studies have begun to elucidate how BLUF domains transmit the light-induced signal and identify related, subsequent changes in the domain structures. Herein, I review progress made to date concerning the physiological functions and the phototransduction mechanism of BLUF proteins.

Abstract: The survey focuses on recent aspects of photochemical reactions to cellular DNA that are implicated through the predominant formation of mostly bipyrimidine photoproducts in deleterious effects of human exposure to sunlight. Recent developments in analytical methods have allowed accurate and quantitative measurements of the main DNA photoproducts in cells and human skin. Highly mutagenic CC and CT bipyrimidine photoproducts, including cyclobutane pyrimidine dimers and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) are generated in low yields with respect to TT and TC photoproducts. Another striking finding deals with the formation of Dewar valence isomers, the third class of bipyrimidine photoproducts that is accounted for by UVA-mediated isomerization of initially UVB generated 6-4PPs. Cyclobutadithymine (T<>T) has been unambiguously shown to be involved in the genotoxicity of UVA radiation. Thus, T<>T is formed in UVA-irradiated cellular DNA according to a direct excitation mechanism with a higher efficiency than oxidatively generated DNA damage that arises mostly through the Type II photosensitization mechanism. C<>C and C<>T are repaired at rates intermediate between those of T<>T and 6-4TT. Evidence has been also provided for the occurrence of photosensitized reactions mediated by exogenous agents that act either in an independent way or through photodynamic effects.

Abstract: Highly complex synthetic gene circuits have been engineered in living organisms to develop systems with new biological properties. A precise trigger to activate or deactivate these complex systems is desired in order to tightly control different parts of a synthetic or natural network. Light represents an excellent tool to achieve this goal as it can be regulated in timing, location, intensity, and wavelength, which allows for precise spatiotemporal control over genetic circuits. Recently, light has been used as a trigger to control the biological function of small molecules, oligonucleotides, and proteins involved as parts in gene circuits. Light activation has enabled the construction of unique systems in living organisms such as band-pass filters and edge-detectors in bacterial cells. Additionally, light also allows for the regulation of intermediate steps of complex dynamic pathways in mammalian cells such as those involved in kinase networks. Herein we describe recent advancements in the area of light-controlled synthetic networks.

Abstract: Optogenetics is an emerging field that combines optical and genetic approaches to non-invasively interfere with cellular events with exquisite spatiotemporal control. Although it arose originally from neuroscience, optogenetics is widely applicable to the study of many different biological systems and the range of applications arising from this technology continues to increase. Moreover, the repertoire of light-sensitive proteins used for devising new optogenetic tools is rapidly expanding. Light, Oxygen, or Voltage sensing (LOV) and Blue-Light-Utilizing flavin adenine dinucleotide (FAD) (BLUF) domains represent new contributors to the optogenetic toolkit. These small (100-140-amino acids) flavoprotein modules are derived from plant and bacterial photoreceptors that respond to UV-A/blue light. In recent years, considerable progress has been made in uncovering the photoactivation mechanisms of both LOV and BLUF domains. This knowledge has been applied in the design of synthetic photoswitches and fluorescent reporters with applications in cell biology and biotechnology. In this review, we summarize the photochemical properties of LOV and BLUF photosensors and highlight some of the recent advances in how these flavoproteins are being employed to artificially regulate and image a variety of biological processes.

Abstract: Plants constantly survey the surrounding environment using several sets of photoreceptors. They can sense changes in the quantity (=intensity) and quality (=wavelength) of light and use this information to adjust their physiological responses, growth, and developmental patterns. In addition to the classical photoreceptors, such as phytochromes, cryptochromes, and phototropins, ZEITLUPE (ZTL), FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1), and LOV KELCH PROTEIN 2 (LKP2) proteins have been recently identified as blue-light photoreceptors that are important for regulation of the circadian clock and photoperiodic flowering. The ZTL/FKF1/LKP2 protein family possesses a unique combination of domains: a blue-light-absorbing LOV (Light, Oxygen, or Voltage) domain along with domains involved in protein degradation. Here, we summarize recent advances in our understanding of the function of the Arabidopsis ZTL/FKF1/LKP2 proteins. We summarize the distinct photochemical properties of their LOV domains and discuss the molecular mechanisms by which the ZTL/FKF1/LKP2 proteins regulate the circadian clock and photoperiodic flowering by controlling blue-light-dependent protein degradation.

Abstract: Molecular switches are the fundamental building blocks in the field of synthetic biology. The majority of these switches is based on protein-protein, protein-DNA or protein-RNA interactions that are responsive towards endogenous metabolites or external stimuli like small molecules or light. By the rational and predictive reassembling of multiple compatible molecular switches, complex synthetic signaling networks can be engineered. Here we review how these switches were used for the regulation of important cellular processes at every level of the signaling cascade. In the second part we review how these switches can be assembled to open- and closed-loop control signaling networks and how these networks can be applied to facilitate cattle reproduction, to treat diabetes or to autonomously detect and cure disease states like gouty arthritis or cancer.

Abstract: Tools for optical control of proteins offer an unprecedented level of spatiotemporal control over biological processes, adding a new layer of experimental opportunity. While use of light-activated cation channels and anion pumps has already revolutionized neurobiology, an emerging class of more general optogenetic tools may have similar transformative effects. These tools consist of light-dependent protein interaction modules that allow control of target protein interactions and localization with light. Such tools are modular and can be applied to regulate a wide variety of biological activities. This chapter reviews the different properties of light-induced dimerization systems, based on plant phytochromes, cryptochromes, and light-oxygen-voltage domain proteins, exploring advantages and limitations of the different systems and practical considerations related to their use. Potential applications of these tools within the neurobiology field, including light control of various signaling pathways, neuronal activity, and DNA recombination and transcription, are discussed.

Abstract: Could combating incurable diseases lie in something as simple as light? This scenario might not be too farfetched due to groundbreaking research in optogenetics. This novel scientific area, where genetically encoded photosensors transform light energy into specifically engineered biological processes, has shown enormous potential. Cell morphology can be changed, signaling pathways can be reprogrammed, and gene expression can be regulated all by the control of light. In biomedical applications where precise cell targeting is essential, non-invasive light has shown great promise. This article provides a summary of the recent advances that utilize light in genetic programming and precise control of engineered biological functions.

Abstract: Photoreceptor flavoproteins of the LOV, BLUF, and cryptochrome families are ubiquitous among the three domains of life and are configured as UVA/blue-light systems not only in plants-their original arena-but also in prokaryotes and microscopic algae. Here, we review these proteins' structure and function, their biological roles, and their evolution and impact in the living world, and underline their growing application in biotechnologies. We present novel developments such as the interplay of light and redox stimuli, emerging enzymatic and biological functions, lessons on evolution from picoalgae, metagenomics analysis, and optogenetics applications.

Abstract: Cryptochromes (CRY) are blue-light receptors that mediate various light responses in plants. The photoexcited CRY molecules undergo several biophysical and biochemical changes, including electron transfer, phosphorylation and ubiquitination, resulting in conformational changes to propagate light signals. Two modes of CRY signal transduction have recently been discovered: the cryptochrome-interacting basic-helix-loop-helix 1 (CIB)-dependent CRY2 regulation of transcription; and the SUPPRESSOR OF PHYA1/CONSTITUTIVELY PHOTOMORPHOGENIC1 (SPA1/COP1)-dependent cryptochrome regulation of proteolysis. Both CRY signaling pathways rely on blue light-dependent interactions between the CRY photoreceptor and its signaling proteins to modulate gene expression changes in response to blue light, leading to altered developmental programs in plants.

Abstract: Synthetic biology aims at the rational design and construction of devices, systems and organisms with desired functionality based on modular well-characterized biological building blocks. Based on first proof-of-concept studies in bacteria a decade ago, synthetic biology strategies have rapidly entered mammalian cell technology providing novel therapeutic solutions. Here we review how biological building blocks can be rewired to interactive regulatory genetic networks in mammalian cells and how these networks can be transformed into open- and closed-loop control configurations for autonomously managing disease phenotypes. In the second part of this tutorial review we describe how the regulatory biological sensors and switches can be transferred from mammalian cell synthetic biology to materials sciences in order to develop interactive biohybrid materials with similar (therapeutic) functionality as their synthetic biological archetypes. We develop a perspective of how the convergence of synthetic biology with materials sciences might contribute to the development of truly interactive and adaptive materials for autonomous operation in a complex environment.