Curated Optogenetic Publication Database

Abstract: Biological systems assemble living materials that are autonomously patterned, can self-repair and can sense and respond to their environment. The field of engineered living materials aims to create novel materials with properties similar to those of natural biomaterials using genetically engineered organisms. Here, we describe an approach to fabricating functional bacterial cellulose-based living materials using a stable co-culture of Saccharomyces cerevisiae yeast and bacterial cellulose-producing Komagataeibacter rhaeticus bacteria. Yeast strains can be engineered to secrete enzymes into bacterial cellulose, generating autonomously grown catalytic materials and enabling DNA-encoded modification of bacterial cellulose bulk properties. Alternatively, engineered yeast can be incorporated within the growing cellulose matrix, creating living materials that can sense and respond to chemical and optical stimuli. This symbiotic culture of bacteria and yeast is a flexible platform for the production of bacterial cellulose-based engineered living materials with potential applications in biosensing and biocatalysis.

Abstract: The current optogenetic toolkit lacks a robust single-component Ca2+-selective ion channel tailored for remote control of Ca2+ signaling in mammals. Existing tools are either derived from engineered channelrhodopsin variants without strict Ca2+ selectivity or based on the stromal interaction molecule 1 (STIM1) that might crosstalk with other targets. Here, we describe the design of a light-operated Ca2+ channel (designated LOCa) by inserting a plant-derived photosensory module into the intracellular loop of an engineered ORAI1 channel. LOCa displays biophysical features reminiscent of the ORAI1 channel, which enables precise optical control over Ca2+ signals and hallmark Ca2+-dependent physiological responses. Furthermore, we demonstrate the use of LOCa to modulate aberrant hematopoietic stem cell self-renewal, transcriptional programming, cell suicide, as well as neurodegeneration in a Drosophila model of amyloidosis.

Abstract: There are several paths when excited molecules return to the ground state. In the case of fluorescent molecules, the dominant path is fluorescence emission that is greatly contributing to bioimaging. Meanwhile, photosensitizers transfer electron or energy from chromophore to the surrounding molecules, including molecular oxygen. Generated reactive oxygen species has potency to attack other molecules by oxidation. In this chapter, we introduce the chromophore-assisted light inactivation (CALI) method using a photosensitizer to inactivate proteins in a spatiotemporal manner and development of CALI tools, which is useful for investigation of protein functions and dynamics, by inactivation of the target molecules. Moreover, photosensitizers with high efficiency make it possible optogenetic control of cell ablation in living organisms and photodynamic therapy. Further development of photosensitizers with different excitation wavelengths will contribute to the investigation of multiple proteins or cell functions through inactivation in the different positions and timings.

Abstract: Photoactivated adenylyl cyclase (PAC) was first discovered to be a sensor for photoavoidance in the flagellate Euglena gracilis. PAC is a flavoprotein that catalyzes the production of cAMP upon illumination with blue light, which enables us to optogenetically manipulate intracellular cAMP levels in various biological systems. Recent progress in genome sequencing has revealed several related proteins in bacteria and ameboflagellates. Among them, the PACs from sulfur bacterium Beggiatoa sp. and cyanobacterium Oscillatoria acuminata have been well characterized, including their crystalline structure. Although there have not been many reported optogenetic applications of PACs so far, they have the potential to be used in various fields within bioscience.

Abstract: Optogenetic systems have been increasingly investigated in the field of biomedicine. Previous studies had found the inhibitory effect of the light-inducible genetic circuits on cancer cell growth. In our study, we applied an AND logic gates to the light-inducible genetic circuits to inhibit the cancer cells more specifically. The circuit would only be activated in the presence of both the human telomerase reverse transcriptase (hTERT) and the human uroplakin II (hUPII) promoter. The activated logic gate led to the expression of the p53 or E-cadherin protein, which could inhibit the biological function of tumor cells. In addition, we split the dCas9 protein to reduce the size of the synthetic circuit compared to the full-length dCas9. This light-inducible system provides a potential therapeutic strategy for future bladder cancer.

Abstract: Membrane receptors play a crucial role in transmitting external signals inside cells. Signal molecule-bound receptors activate multiple downstream pathways, the dynamics of which are modulated by intracellular trafficking. A significant contribution of β-arrestin to intracellular trafficking has been suggested, but the underlying mechanism is poorly understood. Here, we describe a protocol for manipulating β-arrestin-regulated membrane receptor trafficking using photo-induced dimerization of cryptochrome-2 from Arabidopsis thaliana and its binding partner CIBN. Additionally, the protocol guides analytical methods to quantify the changes in localization and modification of membrane receptors during trafficking.

Abstract: Phagophore closure is a critical step during macroautophagy. However, the proteins and mechanisms to regulate this step have been elusive for a long time. In 2017, Rab5 was affirmed to play a role in phagophore closure in yeast. Furthermore, in mammalian cells, ESCRT III was reported to have roles in phagophore closure and mitophagosome closure in vivo in 2018 and 2019, respectively. The role of ESCRT in phagophore closure was confirmed in yeast, both in vivo and in vitro, in 2019. Most importantly, the latter paper found that Atg17 recruited the ESCRT III subunit Snf7 to the phagophore to close it under the control of Rab5. To determine the closure characteristics of autophagosome-like membrane structures in ESCRT mutants, a traditional protease protection assay with immunoblotting was used, accompanied by new techniques that were developed, including immunofluorescence assays, autophagosome completion assays, and the optogenetic closure assay. This study delivered our current understanding of phagophore closure and provided more reference methods to detect membrane closure.

Abstract: The CRISPR-Cas9 system offers targeted genome manipulation with simplicity. Combining the CRISPR-Cas9 with optogenetics technology, we have engineered photoactivatable Cas9 to precisely control the genome sequence in a spatiotemporal manner. Here we provide a detailed protocol for optogenetic genome editing experiments using photoactivatable Cas9, including that for the generation of guide RNA vectors, light-mediated Cas9 activation, and quantification of genome editing efficiency in mammalian cells.

Abstract: Light-inducible gene switches represent a key strategy for the precise manipulation of cellular events in fundamental and applied research. However, the performance of widely used gene switches is limited due to low tissue penetrance and possible phototoxicity of the light stimulus. To overcome these limitations, we engineer optogenetic synthetic transcription factors to undergo liquid-liquid phase separation in close spatial proximity to promoters. Phase separation of constitutive and optogenetic synthetic transcription factors was achieved by incorporation of intrinsically disordered regions. Supported by a quantitative mathematical model, we demonstrate that engineered transcription factor droplets form at target promoters and increase gene expression up to fivefold. This increase in performance was observed in multiple mammalian cells lines as well as in mice following in situ transfection. The results of this work suggest that the introduction of intrinsically disordered domains is a simple yet effective means to boost synthetic transcription factor activity.

Abstract: Dissection of cell signaling requires tools that can mimic spatiotemporal dynamics of individual pathways in living cells. Optogenetic methods enable manipulation of signaling processes with precise timing and local control. In this review, we describe recent optogenetic approaches for regulation of cell signaling, highlight their advantages and limitations, and discuss examples of their application.

Abstract: The extracellular matrix (ECM) comprises a meshwork of biomacromolecules whose composition, architecture, and macroscopic properties, such as mechanics, instruct cell fate decisions during development and disease progression. Current methods implemented in mechanotransduction studies either fail to capture real-time mechanical dynamics or utilize synthetic polymers that lack the fibrillar nature of their natural counterparts. Here we present an optogenetic-inspired tool to construct light-responsive ECM mimetic hydrogels comprised exclusively of natural ECM proteins. Optogenetic tools offer seconds temporal resolution and submicron spatial resolution, permitting researchers to probe cell signaling dynamics with unprecedented precision. Here we demonstrated our approach of using SNAP-tag and its thiol-targeted substrate, benzylguanine-maleimide, to covalently attach blue-light-responsive proteins to collagen hydrogels. The resulting material (OptoGel), in addition to encompassing the native biological activity of collagen, stiffens upon exposure to blue light and softens in the dark. Optogels have immediate use in dissecting the cellular response to acute mechanical inputs and may also have applications in next-generation biointerfacing prosthetics.

Abstract: In nature, photoreceptor proteins undergo molecular responses to light, that exhibit supreme fidelity in time and space and generally occur under mild reaction conditions. To unlock these traits for material science, the light‐induced homodimerization of light‐oxygen‐voltage (LOV) photoreceptors is leveraged to control the assembly of gold nanoparticles. Conjugated to genetically encodable LOV proteins, the nanoparticles are monodispersed in darkness but rapidly assemble into large aggregates upon blue‐light exposure. The work establishes a new modality for reaction control in macromolecular chemistry and thus augurs enhanced precision in space and time in diverse applications of gold nanoparticles.

Abstract: The spatiotemporal organization of oligomeric protein complexes, such as the supramolecular organizing centers (SMOCs) made of MyDDosome and MAVSome, is essential for transcriptional activation of host inflammatory responses and immunometabolism. Light‐inducible assembly of MyDDosome and MAVSome is presented herein to induce activation of nuclear factor‐kB and type‐I interferons. Engineering of SMOCs and the downstream transcription factor permits programmable and customized innate immune operations in a light‐dependent manner. These synthetic molecular tools will likely enable optical and user‐defined modulation of innate immunity at a high spatiotemporal resolution to facilitate mechanistic studies of distinct modes of innate immune activations and potential intervention of immune disorders and cancer.

Abstract: Microbial synthesis of chemicals typically requires the redistribution of metabolic flux toward the synthesis of targeted products. Dynamic control is emerging as an effective approach for solving the hurdles mentioned above. As light could control the cell behavior in a spatial and temporal manner, the optogenetic-CRISPR interference (opto-CRISPRi) technique that allocates the metabolic resources according to different optical signal frequencies will enable bacteria to be controlled between the growth phase and the production stage. In this study, we applied a blue light-sensitive protein EL222 to regulate the expression of the dCpf1-mediated CRISPRi system that turns off the competitive pathways and redirects the metabolic flux toward the heterologous muconic acid synthesis in Escherichia coli. We found that the opto-CRISPRi system dynamically regulating the suppression of the central metabolism and competitive pathways could increase the muconic acid production by 130%. These results demonstrated that the opto-CRISPRi platform is an effective method for enhancing chemical synthesis with broad utilities.

Abstract: Irf6 and Esrp1 are important for palate development across vertebrates. In zebrafish, we found that irf6 regulates the expression of esrp1 We detailed overlapping Irf6 and Esrp1/2 expression in mouse orofacial epithelium. In zebrafish, irf6 and esrp1/2 share expression in periderm, frontonasal ectoderm and oral epithelium. Genetic disruption of irf6 and esrp1/2 in zebrafish resulted in cleft of the anterior neurocranium. The esrp1/2 mutant also developed cleft of the mouth opening. Lineage tracing of cranial neural crest cells revealed that the cleft resulted not from migration defect, but from impaired chondrogenesis. Analysis of aberrant cells within the cleft revealed expression of sox10, col1a1 and irf6, and these cells were adjacent to krt4 + and krt5 + cells. Breeding of mouse Irf6; Esrp1; Esrp2 compound mutants suggested genetic interaction, as the triple homozygote and the Irf6; Esrp1 double homozygote were not observed. Further, Irf6 heterozygosity reduced Esrp1/2 cleft severity. These studies highlight the complementary analysis of Irf6 and Esrp1/2 in mouse and zebrafish, and identify a unique aberrant cell population in zebrafish expressing sox10, col1a1 and irf6 Future work characterizing this cell population will yield additional insight into cleft pathogenesis.

Abstract: Living organisms have evolved sophisticated cell-mediated biomineralization mechanisms to build structurally ordered, environmentally adaptive composite materials. Despite advances in biomimetic mineralization research, it remains difficult to produce mineralized composites that integrate the structural features and 'living' attributes of their natural counterparts. Here, inspired by natural graded materials, we developed living patterned and gradient composites by coupling light-inducible bacterial biofilm formation with biomimetic hydroxyapatite (HA) mineralization. We showed that both the location and the degree of mineralization could be regulated by tailoring functional biofilm growth with spatial and biomass density control. The cells in the composites remained viable and could sense and respond to environmental signals. Additionally, the composites exhibited a maximum 15-fold increase in Young's modulus after mineralization and could be applied to repair damage in a spatially controlled manner. Beyond insights into the mechanism of formation of natural graded composites, our study provides a viable means of fabricating living composites with dynamic responsiveness and environmental adaptability.

Abstract: Plants measure light quality, intensity, and duration to coordinate growth and development with daily and seasonal changes in environmental conditions; however, the molecular details linking photochemistry to signal transduction remain incomplete. Two closely related light, oxygen, or voltage (LOV) domain-containing photoreceptor proteins, ZEITLUPE (ZTL) and FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1), divergently regulate the protein stability of circadian clock and photoperiodic flowering components to mediate daily and seasonal development. Using structural approaches, we identified that mutations at the Gly46 position led to global rearrangements of the ZTL dimer interface in the isolated ZTL-LOV domain. Specifically, G46S and G46A variants induce a 180° rotation about the ZTL-LOV dimer interface that is coupled to ordering of N- and C-terminal signaling elements. These conformational changes hinge upon rotation of a C-terminal Gln residue (Gln154) analogous to that present in light-state structures of ZTL. In contrast to other LOV proteins, a Q154L variant retains light-state interactions with GIGANTEA (GI), thereby indicating N5 protonation is not required for ZTL signaling. The results presented herein confirm a divergent signaling mechanism within ZTL, whereby steric and electronic effects following adduct formation can be sufficient for signal propagation in LOV proteins containing a Gly residue at position 46. Examination of bacterial LOV structures with Gly residues at the equivalent position suggests that mechanisms of signal transduction in LOV proteins may be fluid across the LOV protein family.

Abstract: Precise genetic engineering in specific cell types within an intact organism is intriguing yet challenging, especially in a spatiotemporal manner without the interference caused by chemical inducers. Here we engineered a photoactivatable Dre recombinase based on the identification of an optimal split site and demonstrated that it efficiently regulated transgene expression in mouse tissues spatiotemporally upon blue light illumination. Moreover, through a double-floxed inverted open reading frame strategy, we developed a Cre-activated light-inducible Dre (CALID) system. Taking advantage of well-defined cell-type-specific promoters or a well-established Cre transgenic mouse strain, we demonstrated that the CALID system was able to activate endogenous reporter expression for either bulk or sparse labeling of CaMKIIα-positive excitatory neurons and parvalbumin interneurons in the brain. This flexible and tunable system could be a powerful tool for the dissection and modulation of developmental and genetic complexity in a wide range of biological systems.

Abstract: The small GTPases Rac1 and Rap1 can fulfill multiple cellular functions because their activation kinetics and localization are precisely controlled. To probe the role of their spatio-temporal dynamics, we generated optogenetic tools that activate or inhibit endogenous Rac and Rap1 in living cells. An improved version of the light-induced dimerization (iLID) system [1] was used to control plasma membrane localization of protein domains that specifically activate or inactivate Rap1 and Rac (Tiam1 and Chimerin for Rac, RasGRP2 and Rap1GAP for Rap1 [2–5]). Irradiation yielded a 50-230% increase in the concentration of these domains at the membrane, leading to effects on cell morphodynamics consistent with the known roles of Rac1 and Rap1.

Abstract: Eukaryotic cells typically form a single, round nucleus after mitosis, and failures to do so can compromise genomic integrity. How mammalian cells form such a nucleus remains incompletely understood. NuMA is a spindle protein whose disruption results in nuclear fragmentation. What role NuMA plays in nuclear integrity, and whether its perceived role stems from its spindle function, are unclear. Here, we use live imaging to demonstrate that NuMA plays a spindle-independent role in forming a single, round nucleus. NuMA keeps the decondensing chromosome mass compact at mitotic exit and promotes a mechanically robust nucleus. NuMA's C terminus binds DNA in vitro and chromosomes in interphase, while its coiled-coil acts as a central regulatory and structural element: it prevents NuMA from binding chromosomes at mitosis, regulates its nuclear mobility, and is essential for nuclear formation. Thus, NuMA plays a structural role over the cell cycle, building and maintaining the spindle and nucleus, two of the cell's largest structures.

Abstract: Heterotrimeric G proteins are central mediators of cellular signal transduction. They receive, process, and transduce signals from G protein-coupled receptors to downstream effectors. Since their discovery, a number of optical sensors of G protein localization and function have been developed and applied in living systems. In this minireview, we provide an overview of existing G protein-based sensors and the experimental approaches they utilize, with emphasis on live-cell imaging techniques. We outline recent advances, as well as identify current challenges and likely future directions in the field of G protein sensor development.

Abstract: Alzheimer's Disease (AD) has long been associated with accumulation of extracellular amyloid plaques (Aβ) originating from the Amyloid Precursor Protein. Plaques have, however, been discovered in healthy individuals and not all AD brains show plaques, suggesting that extracellular Aβ aggregates may play a smaller role than anticipated. One limitation to studying Aβ peptide in vivo during disease progression is the inability to induce aggregation in a controlled manner. We developed an optogenetic method to induce Aβ aggregation and tested its biological influence in three model organisms-D. melanogaster, C. elegans and D. rerio. We generated a fluorescently labeled, optogenetic Aβ peptide that oligomerizes rapidly in vivo in the presence of blue light in all organisms. Here, we detail the procedures for expressing this fusion protein in animal models, investigating the effects on the nervous system using time lapse light-sheet microscopy, and performing metabolic assays to measure changes due to intracellular Aβ aggregation. This method, employing optogenetics to study the pathology of AD, allows spatial and temporal control in vivo that cannot be achieved by any other method at present.

Abstract: The folding of epithelial sheets is important for tissues, organs and embryos to attain their proper shapes. Epithelial folding requires subcellular modulations of mechanical forces in cells. Fold formation has mainly been attributed to mechanical force generation at apical cell sides, but several studies indicate a role of mechanical tension at lateral cell sides in this process. However, whether lateral tension increase is sufficient to drive epithelial folding remains unclear. Here, we have used optogenetics to locally increase mechanical force generation at apical, lateral or basal sides of epithelial Drosophila wing disc cells, an important model for studying morphogenesis. We show that optogenetic recruitment of RhoGEF2 to apical, lateral or basal cell sides leads to local accumulation of F-actin and increase in mechanical tension. Increased lateral tension, but not increased apical or basal tension, results in sizeable fold formation. Our results stress the diversification of folding mechanisms between different tissues and highlight the importance of lateral tension increase for epithelial folding.

Abstract: Local cell contraction pulses play important roles in tissue and cell morphogenesis. Here, we improve a chemo-optogenetic approach and apply it to investigate the signal network that generates these pulses. We use these measurements to derive and parameterize a system of ordinary differential equations describing temporal signal network dynamics. Bifurcation analysis and numerical simulations predict a strong dependence of oscillatory system dynamics on the concentration of GEF-H1, an Lbc-type RhoGEF, which mediates the positive feedback amplification of Rho activity. This prediction is confirmed experimentally via optogenetic tuning of the effective GEF-H1 concentration in individual living cells. Numerical simulations show that pulse amplitude is most sensitive to external inputs into the myosin component at low GEF-H1 concentrations and that the spatial pulse width is dependent on GEF-H1 diffusion. Our study offers a theoretical framework to explain the emergence of local cell contraction pulses and their modulation by biochemical and mechanical signals.

Abstract: Enzymatic reactions in cells are well organized into different compartments, among which protein-based membraneless compartments formed through liquid-liquid phase separation (LLPS) are believed to play important roles1,2. Hijacking them for our own purpose has promising applications in metabolic engineering3. Yet, it is still hard to precisely and dynamically control target enzymatic reactions in those compartments4. To address those problems, we developed Photo-Activated Switch in E. coli (PhASE), based on phase separating scaffold proteins and optogenetic tools. In this system, a protein of interest (POI) can be enriched up to 15-fold by LLPS-based compartments from cytosol within only a few seconds once activated by light, and become fully dispersed again within 15 minutes. Furthermore, we explored the potentiality of the LLPS-based compartment in enriching small organic molecules directly via chemical-scaffold interaction. With enzymes and substrates co-localized under light induction, the overall reaction efficiency could be enhanced. Using luciferin and catechol oxidation as model enzymatic reactions, we found that they could accelerate 2.3-fold and 1.6-fold, respectively, when regulated by PhASE. We anticipate our system to be an extension of the synthetic biology toolkit, facilitating rapid recruitment and release of POIs, and reversible regulation of enzymatic reactions.