Showing 1 - 25 of 121 results
Optogenetic regulation of transcription.
Optogenetics has become widely recognized for its success in real-time control of brain neurons by utilizing nonmammalian photosensitive proteins to open or close membrane channels. Here we review a less well known type of optogenetic constructs that employs photosensitive proteins to transduce the signal to regulate gene transcription, and its possible use in medicine. One of the problems with existing gene therapies is that they could remain active indefnitely while not allowing regulated transgene production on demand. Optogenetic regulation of transcription (ORT) could potentially be used to regulate the production of a biological drug in situ, by repeatedly applying light to the tissue, and inducing expression of therapeutic transgenes when needed. Red and near infrared wavelengths, which are capable of penetration into tissues, have potential for therapeutic applications. Existing ORT systems are reviewed herein with these considerations in mind.
Optogenetics: A Primer for Chemists.
The field of optogenetics uses genetically encoded, light-responsive proteins to control physiological processes. This technology has been hailed as the one of the ten big ideas in brain science in the past decade, the breakthrough of the decade, and the method of the year in 2010 and again in 2014. The excitement evidenced by these proclamations is confirmed by a couple of impressive numbers. The term "optogenetics" was coined in 2006. As of December 2017, "optogenetics" is found in the title or abstract of almost 1600 currently funded National Institutes of Health grants. In addition, nearly 600 reviews on optogenetics have appeared since 2006, which averages out to approximately one review per week! However, in spite of these impressive numbers, the potential applications and implications of optogenetics are not even close to being fully realized. This is due, in large part, to the challenges associated with the design of optogenetic analogs of endogenous proteins. This review is written from a chemist's perspective, with a focus on the molecular strategies that have been developed for the construction of optogenetic proteins.
New approaches for solving old problems in neuronal protein trafficking.
Fundamental cellular properties are determined by the repertoire and abundance of proteins displayed on the cell surface. As such, the trafficking mechanisms for establishing and maintaining the surface proteome must be tightly regulated for cells to respond appropriately to extracellular cues, yet plastic enough to adapt to ever-changing environments. Not only are the identity and abundance of surface proteins critical, but in many cases, their regulated spatial positioning within surface nanodomains can greatly impact their function. In the context of neuronal cell biology, surface levels and positioning of ion channels and neurotransmitter receptors play essential roles in establishing important properties, including cellular excitability and synaptic strength. Here we review our current understanding of the trafficking pathways that control the abundance and localization of proteins important for synaptic function and plasticity, as well as recent technological advances that are allowing the field to investigate protein trafficking with increasing spatiotemporal precision.
Induction of signal transduction using non-channelrhodopsin-type optogenetic tools.
Signal transductions are the basis for all cellular functions. Previous studies investigating signal transductions mainly relied on pharmacological inhibition, RNA interference, and constitutive active/dominant negative protein expression systems. However, such studies do not allow the modulation of protein activity in cells, tissues, and organs in animals with high spatial and temporal precision. Recently, non-channelrhodopsin-type optogenetic tools for regulating signal transduction have emerged. These photoswitches address several disadvantages of previous techniques, and allow us to control a variety of signal transductions such as cell membrane dynamics, calcium signaling, lipid signaling, and apoptosis. In this review, we summarize recent advances in the development of such photoswitches and how these optotools are applied to signaling processes.
Illuminating developmental biology with cellular optogenetics.
In developmental biology, localization is everything. The same stimulus-cell signaling event or expression of a gene-can have dramatically different effects depending on the time, spatial position, and cell types in which it is applied. Yet the field has long lacked the ability to deliver localized perturbations with high specificity in vivo. The advent of optogenetic tools, capable of delivering highly localized stimuli, is thus poised to profoundly expand our understanding of development. We describe the current state-of-the-art in cellular optogenetic tools, review the first wave of major studies showcasing their application in vivo, and discuss major obstacles that must be overcome if the promise of developmental optogenetics is to be fully realized.
Optogenetically controlled protein kinases for regulation of cellular signaling.
Protein kinases are involved in the regulation of many cellular processes including cell differentiation, survival, migration, axon guidance and neuronal plasticity. A growing set of optogenetic tools, termed opto-kinases, allows activation and inhibition of different protein kinases with light. The optogenetic regulation enables fast, reversible and non-invasive manipulation of protein kinase activities, complementing traditional methods, such as treatment with growth factors, protein kinase inhibitors or chemical dimerizers. In this review, we summarize the properties of the existing optogenetic tools for controlling tyrosine kinases and serine-threonine kinases. We discuss how the opto-kinases can be applied for studies of spatial and temporal aspects of protein kinase signaling in cells and organisms. We compare approaches for chemical and optogenetic regulation of protein kinase activity and present guidelines for selection of opto-kinases and equipment to control them with light. We also describe strategies to engineer novel opto-kinases on the basis of various photoreceptors.
Optogenetics in cancer drug discovery.
The discovery and domestication of biomolecules that respond to light has taken a light of its own, providing new molecular tools with incredible spatio-temporal resolution to manipulate cellular behavior. Areas covered: The authors herein analyze the current optogenetic tools in light of their current, and potential, uses in cancer drug discovery, biosafety and cancer biology. Expert opinion: The pipeline from drug discovery to the clinic is plagued with drawbacks, where most drugs fail in either efficacy or safety. These issues require the redesign of the pipeline and the development of more controllable/personalized therapies. Light is, aside from inexpensive, almost harmless if used appropriately, can be directed to single cells or organs with controllable penetration, and comes in a variety of wavelengths. Light-responsive systems can activate, inhibit or compensate cell signaling pathways or specific cellular events, allowing the specific control of the genome and epigenome, and modulate cell fate and transformation. These synthetic molecular tools have the potential to revolutionize drug discovery and cancer research.
Optogenetic Reconstitution for Determining the Form and Function of Membraneless Organelles.
It has recently become clear that large-scale macromolecular self-assembly is a rule, rather than an exception, of intracellular organization. A growing number of proteins and RNAs have been shown to self-assemble into micrometer-scale clusters that exhibit either liquid-like or gel-like properties. Given their proposed roles in intracellular regulation, embryo development, and human disease, it is becoming increasingly important to understand how these membraneless organelles form and to map their functional consequences for the cell. Recently developed optogenetic systems make it possible to acutely control cluster assembly and disassembly in live cells, driving the separation of proteins of interest into liquid droplets, hydrogels, or solid aggregates. Here we propose that these approaches, as well as their evolution into the next generation of optogenetic biophysical tools, will allow biologists to determine how the self-assembly of membraneless organelles modulates diverse biochemical processes.
Split Cas9, not hairs - advancing the therapeutic index of CRISPR technology.
The discovery that the bacterial CRISPR/Cas9 system can be translated into mammalian cells continues to have an unprecedented impact on the biomedical research community, as it largely facilitates efforts to experimentally interrogate or therapeutically modify the cellular genome. In particular, CRISPR promises the ability to correct disease-associated genetic defects, or to target and destroy invading foreign DNA, in a simple, efficient and selective manner directly in affected human cells or tissues. Here, we highlight a set of exciting new strategies that aim at further increasing the therapeutic index of CRISPR technologies, by reducing the size of Cas9 expression cassettes and thus enhancing their compatibility with viral gene delivery vectors. Specifically, we discuss the concept of splitCas9 whereby the Cas9 holo-protein is segregated into two parts that are expressed individually and reunited in the cell by various means, including use of (i) the gRNA as a scaffold for Cas9 assembly, (ii) the rapamycin-controlled FKBP/FRB system, (iii) the light-regulated Magnet system, or (iv) inteins. We describe how these avenues, despite pursuing the identical aim, differ in critical features comprising the extent of spatio-temporal control of CRISPR activity, and discuss additional improvements to their efficiency or specificity that should foster their clinical translation.
CRISPR/dCas9 Switch Systems for Temporal Transcriptional Control.
In a swift revolution, CRISPR/Cas9 has reshaped the means and ease of interrogating biological questions. Particularly, mutants that result in a nuclease-deactivated Cas9 (dCas9) provide scientists with tools to modulate transcription of genomic loci at will by targeting transcriptional effector domains. To interrogate the temporal order of events during transcriptional regulation, rapidly inducible CRISPR/dCas9 systems provide previously unmet molecular tools. In only a few years of time, numerous light and chemical-inducible switches have been applied to CRISPR/dCas9 to generate dCas9 switches. As these inducible switch systems are able to modulate dCas9 directly at the protein level, they rapidly affect dCas9 stability, activity, or target binding and subsequently rapidly influence downstream transcriptional events. Here we review the current state of such biotechnological CRISPR/dCas9 enhancements. Specifically we provide details on their flaws and strengths and on the differences in molecular design between the switch systems. With this we aim to provide a selection guide for researchers with keen interest in rapid temporal control over transcriptional modulation through the CRISPR/dCas9 system.
Light-induced chromophore and protein responses and mechanical signal transduction of BLUF proteins.
Photoreceptor proteins have been used to study how protein conformational changes are induced by alterations in their environments and how their signals are transmitted to downstream factors to dictate physiological responses. These proteins are attractive models because their signal transduction aspects and structural changes can be precisely regulated in vivo and in vitro based on light intensity. Among the known photoreceptors, members of the blue light-using flavin (BLUF) protein family have been well characterized with regard to how they control various light-dependent physiological responses in several microorganisms. Herein, we summarize our current understanding of their photoactivation and signal-transduction mechanisms. For signal transduction, we review recent studies concerning how the BLUF protein, PixD, transmits a light-induced signal to its downstream factor, PixE, to modulate phototaxis of the cyanobacterium Synechocystis sp. PCC6803.
Optogenetic tools for cell biological applications.
Abstract not available.
Illuminating information transfer in signaling dynamics by optogenetics.
Cells receive diverse signaling cues from their environment that trigger cascades of biochemical reactions in a dynamic manner. Single-cell imaging technologies have revealed that not only molecular species but also dynamic patterns of signaling inputs determine the fates of signal-receiving cells; however it has been challenging to elucidate how such dynamic information is delivered and decoded in complex networks of inter-cellular and inter-molecular interactions. The recent development of optogenetic technology with photo-sensitive proteins has changed this situation; the combination of microscopy and optogenetics provides fruitful insights into the mechanism of dynamic information processing at the single-cell level. Here, we review recent efforts to visualize the flows of dynamic patterns in signaling pathways, which utilize methods integrating single-cell imaging and optogenetics.
Emerging approaches for spatiotemporal control of targeted genome with inducible CRISPR-Cas9.
The breakthrough CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 (CRISPR-associated protein 9) nuclease has revolutionized our ability in genome engineering. Although Cas9 is already a powerful tool for simple and efficient target endogenous gene manipulation, further engineering of Cas9 will improve the performance of Cas9, such as gene-editing efficiency and accuracy in vivo, and expand the application possibility of this Cas9 technology. The emerging inducible Cas9 methods, which can control the activity of Cas9 using an external stimulus such as chemicals and light, have the potential to provide spatiotemporal gene manipulation in user-defined cell population at a specific time and improve the accuracy of Cas9-mediated genome editing. In this review, we focus on the recent advance in inducible Cas9 technologies, especially light-inducible Cas9, and related methodologies, and also discuss future directions of this emerging tools.
New Developments in CRISPR/Cas-based Functional Genomics and their Implications for Research using Zebrafish.
Genome editing using CRISPR/Cas9 has advanced very rapidly in its scope, versatility and ease of use. Zebrafish (Danio rerio) has been one of the vertebrate model species where CRISPR/Cas9 has been applied very extensively for many different purposes and with great success. In particular, disease modeling in zebrafish is useful for testing specific gene variants for pathogenicity in a preclinical setting. Here we describe multiple advances in diverse species and systems that can improve genome editing in zebrafish. To achieve temporal and spatial precision of genome editing, many new technologies can be applied in zebrafish such as artificial transcription factors, drug-inducible or optogenetically-driven expression of Cas9, or chemically-inducible activation of Cas9. Moreover, chemically- or optogenetically-inducible reconstitution of dead Cas9 (catalytically inactive, dCas9) can enable spatiotemporal control of gene regulation. In addition to controlling where and when genome editing occurs, using oligonucleotides allows for the introduction (knock-in) of precise modifications of the genome. We review recent trends to improve the precision and efficiency of oligo-based point mutation knock-ins and discuss how these improvements can apply to work in zebrafish. Similarly to how chemical mutagenesis enabled the first genetic screens in zebrafish, multiplexed sgRNA libraries and Cas9 can enable the next revolutionary transition in how genetic screens are performed in this species. We discuss the first examples and prospects of approaches using sgRNAs as specific and effective mutagens. Moreover, we have reviewed methods aimed at measuring the phenotypes of single cells after their mutagenic perturbation with vectors encoding individual sgRNAs. These methods can range from different cell-based reporters to single-cell RNA sequencing and can serve as great tools for high-throughput genetic screens.
Cell membrane dynamics induction using optogenetic tools.
Structures arising from actin-based cell membrane movements, including ruffles, lamellipodia, and filopodia, play important roles in a broad spectrum of cellular functions, such as cell motility, axon guidance in neurons, wound healing, and micropinocytosis. Previous studies investigating these cell membrane dynamics often relied on pharmacological inhibition, RNA interference, and constitutive active/dominant negative protein expression systems. However, such studies did not allow the modulation of protein activity at specific regions of cells, tissues, and organs in animals with high spatial and temporal precision. Recently, optogenetic tools for inducing cell membrane dynamics have been developed which address several of the disadvantages of previous techniques. In a recent study, we developed a powerful optogenetic tool, called the Magnet system, to change cell membrane dynamics through Tiam1 and PIP3 signal transductions with high spatial and temporal resolution. In this review, we summarize recent advances in optogenetic tools that allow us to induce actin-regulated cell membrane dynamics and unique membrane ruffles that we discovered using our Magnet system.
Shedding light on the role of cAMP in mammalian sperm physiology.
Mammalian fertilization relies on sperm finding the egg and penetrating the egg vestments. All steps in a sperm's lifetime crucially rely on changes in the second messenger cAMP (cyclic adenosine monophosphate). In recent years, it has become clear that signal transduction in sperm is not a continuum, but rather organized in subcellular domains, e.g. the sperm head and the sperm flagellum, with the latter being further separated into the midpiece, principal piece, and endpiece. To understand the underlying signaling pathways controlling sperm function in more detail, experimental approaches are needed that allow to study sperm signaling with spatial and temporal precision. Here, we will give a comprehensive overview on cAMP signaling in mammalian sperm, describing the molecular players involved in these pathways and the sperm functions that are controlled by cAMP. Furthermore, we will highlight recent advances in analyzing and manipulating sperm signaling with spatio-temporal precision using light.
Optogenetic Tools for Subcellular Applications in Neuroscience.
The ability to study cellular physiology using photosensitive, genetically encoded molecules has profoundly transformed neuroscience. The modern optogenetic toolbox includes fluorescent sensors to visualize signaling events in living cells and optogenetic actuators enabling manipulation of numerous cellular activities. Most optogenetic tools are not targeted to specific subcellular compartments but are localized with limited discrimination throughout the cell. Therefore, optogenetic activation often does not reflect context-dependent effects of highly localized intracellular signaling events. Subcellular targeting is required to achieve more specific optogenetic readouts and photomanipulation. Here we first provide a detailed overview of the available optogenetic tools with a focus on optogenetic actuators. Second, we review established strategies for targeting these tools to specific subcellular compartments. Finally, we discuss useful tools and targeting strategies that are currently missing from the optogenetics repertoire and provide suggestions for novel subcellular optogenetic applications.
Applications of optobiology in intact cells and multi-cellular organisms.
Temporal kinetics and spatial coordination of signal transduction in cells are vital for cell fate determination. Tools that allow for precise modulation of spatiotemporal regulation of intracellular signaling in intact cells and multicellular organisms remain limited. The emerging optobiological approaches use light to control protein-protein interaction in live cells and multicellular organisms. Optobiology empowers light-mediated control of diverse cellular and organismal functions such as neuronal activity, intracellular signaling, gene expression, cell proliferation, differentiation, migration, and apoptosis. In this review, we highlight recent developments in optobiology, focusing on new features of second-generation optobiological tools. We cover applications of optobiological approaches in the study of cellular and organismal functions, discuss current challenges, and present our outlook. Taking advantage of the high spatial and temporal resolution of light control, optobiology promises to provide new insights into the coordination of signaling circuits in intact cells and multicellular organisms.
Genetically Encoded Photoactuators and Photosensors for Characterization and Manipulation of Pluripotent Stem Cells.
Our knowledge of pluripotent stem cell biology has advanced considerably in the past four decades, but it has yet to deliver on the great promise of regenerative medicine. The slow progress can be mainly attributed to our incomplete understanding of the complex biologic processes regulating the dynamic developmental pathways from pluripotency to fully-differentiated states of functional somatic cells. Much of the difficulty arises from our lack of specific tools to query, or manipulate, the molecular scale circuitry on both single-cell and organismal levels. Fortunately, the last two decades of progress in the field of optogenetics have produced a variety of genetically encoded, light-mediated tools that enable visualization and control of the spatiotemporal regulation of cellular function. The merging of optogenetics and pluripotent stem cell biology could thus be an important step toward realization of the clinical potential of pluripotent stem cells. In this review, we have surveyed available genetically encoded photoactuators and photosensors, a rapidly expanding toolbox, with particular attention to those with utility for studying pluripotent stem cells.
Synthetic biological approaches to optogenetically control cell signaling.
Precise spatial and temporal control of cellular processes is in life sciences a highly sought-after capability. In the recent years, this goal has become progressively achievable through the field of optogenetics, which utilizes light as a non-invasive means to control genetically encoded light-responsive proteins. The latest optogenetic systems, such as those for control of subcellular localization or cellular decision-making and tissue morphogenesis provide us with insights to gain a deeper understanding of the cellular inner workings. Besides, they hold a potential for further development into biomedical applications, from in vitro optogenetics-assisted drug candidate screenings to light-controlled gene therapy and tissue engineering.
At Light Speed: Advances in Optogenetic Systems for Regulating Cell Signaling and Behavior.
Cells are bombarded by extrinsic signals that dynamically change in time and space. Such dynamic variations can exert profound effects on behaviors, including cellular signaling, organismal development, stem cell differentiation, normal tissue function, and disease processes such as cancer. Although classical genetic tools are well suited to introduce binary perturbations, new approaches have been necessary to investigate how dynamic signal variation may regulate cell behavior. This fundamental question is increasingly being addressed with optogenetics, a field focused on engineering and harnessing light-sensitive proteins to interface with cellular signaling pathways. Channelrhodopsins initially defined optogenetics; however, through recent use of light-responsive proteins with myriad spectral and functional properties, practical applications of optogenetics currently encompass cell signaling, subcellular localization, and gene regulation. Now, important questions regarding signal integration within branch points of signaling networks, asymmetric cell responses to spatially restricted signals, and effects of signal dosage versus duration can be addressed. This review summarizes emerging technologies and applications within the expanding field of optogenetics.
Engineering genetically-encoded tools for optogenetic control of protein activity.
Optogenetic tools offer fast and reversible control of protein activity with subcellular spatial precision. In the past few years, remarkable progress has been made in engineering photoactivatable systems regulating the activity of cellular proteins. In this review, we discuss general strategies in designing and optimizing such optogenetic tools and highlight recent advances in the field, with specific focus on applications regulating protein catalytic activity.
Illuminating developmental biology through photochemistry.
Developmental biology has been continually shaped by technological advances, evolving from a descriptive science into one immersed in molecular and cellular mechanisms. Most recently, genome sequencing and 'omics' profiling have provided developmental biologists with a wealth of genetic and biochemical information; however, fully translating this knowledge into functional understanding will require new experimental capabilities. Photoactivatable probes have emerged as particularly valuable tools for investigating developmental mechanisms, as they can enable rapid, specific manipulations of DNA, RNA, proteins, and cells with spatiotemporal precision. In this Perspective, we describe optochemical and optogenetic systems that have been applied in multicellular organisms, insights gained through the use of these probes, and their current limitations. We also suggest how chemical biologists can expand the reach of photoactivatable technologies and bring new depth to our understanding of organismal development.
Optogenetics: Switching with red and blue.
Abstract not available.