Curated Optogenetic Publication Database

Abstract: Light as an environmental signal can effectively regulate various biological processes in microbial systems. Optical and optogenetic tools are able to utilize light for precise control methods with minimal interference. Recently, research on these tools has extended to the field of microbiology. Distinguishing from existing reviews, this review narrows the scope of application into food sector, focusing on advances in optical and optogenetic tools for microbial control, including optical tools targeting pathogenic or probiotic bacteria for non-thermal sterilization, antimicrobial photodynamic therapy, or photobiomodulation, combined with nanomaterials as photosensors for food analysis. As well as using optogenetic tools for more convenient and precise control in food production processes, covering reversible induction, metabolic flux regulation, biofilm formation, and inhibition. These tools offer new solutions to goals that cannot be achieved by traditional methods, and they are still maturing to explore other uses in the food field.

Abstract: Abstract Tauopathy is a spectrum of diseases characterized by fibrillary tau aggregate formation in neurons and glial cells in the brain. Tau aggregation originates in the brainstem and entorhinal cortex and then spreads throughout the brain in Alzheimer’s disease (AD), which is the most prevalent type of tauopathy. Understanding the mechanism by which locally developed tau pathology propagates throughout the brain is crucial for comprehending AD pathogenesis. Therefore, a novel model of tau pathology that artificially induces tau aggregation in targeted cells at specific times is essential. This study describes a novel optogenetic module, OptoTau, which is a human tau with the P301L mutation fused with a photosensitive protein CRY2olig, inducing various forms of tau according to the temporal pattern of blue light illumination pattern. Continuous blue light illumination for 12 h to Neuro2a cells that stably express OptoTau (OptoTauKI cells) formed clusters along microtubules, many of which eventually accumulated in aggresomes. Conversely, methanol-resistant tau aggregation was formed when alternating light exposure and darkness in 30-min cycles for 8 sets per day were repeated over 8 days. Methanol-resistant tau was induced more rapidly by repeating 5-min illumination followed by 25-min darkness over 24 h. These results indicate that OptoTau induced various tau aggregation stages based on the temporal pattern of blue light exposure. Thus, this technique exhibits potential as a novel approach to developing specific tau aggregation in targeted cells at desired time points.

Abstract: Research for biopharmaceutical production processes with mammalian cells steadily aims to enhance the cell-specific productivity as a means for optimizing total productivities of bioreactors. Whereas current technologies such as pH, temperature, and osmolality shift require modifications of the cultivation medium, the use of optogenetic switches in recombinant producer cells might be a promising contact-free alternative. However, the proper application of optogenetically engineered cells requires a detailed understanding of basic cellular responses of cells that do not yet contain the optogenetic switches. The knowhow of ideal light exposure to enable the optimum use of related approaches is missing so far. Consequently, the current study set out to find optimum conditions for IgG1 producing Chinese hamster ovary (CHO) cells which were exposed to blue LED light. Growth characteristics, cell-specific productivity using enzyme-linked immunosorbent assay, as well as cell cycle distribution using flow cytometry were analyzed. Whereas too harsh light exposure causes detrimental growth effects that could be compensated with antioxidants, a surprising boost of cell-specific productivity by 57% occurred at optimum high light doses. The increase coincided with an increased number of cells in the G1 phase of the cell cycle after 72 h of illumination. The results present a promising new approach to boost biopharmaceutical productivity of mammalian cells simply by proper light exposure without any further optogenetic engineering. KEY POINTS: • Blue LED light hinders growth in CHO DP-12 cells • Antioxidants protect to a certain degree from blue light effects • Illumination with blue LED light raises cell-specific productivity.

Abstract: The use of optogenetic tools offers an excellent method for spatially and temporally regulated gene and protein expression in cell therapeutic approaches. This could be useful as a concomitant therapeutic measure, especially in small body compartments such as the inner ear, for example, during cochlea implantation, to enhance neuronal cell survival and function. Here, we used the blue light activatable CRY2/CIB system to induce transcription of brain-derived neurotrophic factor (BDNF) in human cells. Transfection with three plasmids, encoding for the optogenetic system and the target, as well as illumination protocols were optimized with luciferase as a reporter to achieve the highest protein expression in human embryonic kidney cells 293. Illumination was performed either with a light-emitting diode or with a scanning laser setup. The optimized protocols were applied for the production of BDNF. We could demonstrate a 64.7-fold increase of BNDF expression upon light induction compared to the basal level. Light-induced BDNF was biologically active and enhanced survival and neurite growth of spiral ganglion neurons. The optogenetic approach can be transferred to autologous cell systems, such as bone marrow-derived mesenchymal stem cells, and thus represents the first optogenetic neurotrophic therapy for the inner ear.

Abstract: Post-translational modifications (PTMs) are indispensable modulators of protein activity. Most cellular behaviours, from cell division to cytoskeletal organization, are controlled by PTMs, their miss-regulation being associated with a plethora of human diseases. Traditionally, the role of PTMs has been studied employing biochemical techniques. However, these approaches fall short when studying PTM dynamics in vivo. In recent years, functionalized protein binders have allowed the post-translational modification of endogenous proteins by bringing an enzymatic domain in close proximity to the protein they recognize. To date, most of these methods lack the temporal control necessary to understand the complex effects triggered by PTMs. In this study, we have developed a method to phosphorylate endogenous Myosin in a light-inducible manner. The method relies both on nanobody-targeting and light-inducible activation in order to achieve both tight specificity and temporal control. We demonstrate that this technology is able to disrupt cytoskeletal dynamics during Drosophila embryonic development. Together, our results highlight the potential of combining optogenetics and protein binders for the study of the proteome in multicellular systems.

Abstract: Mutations of the cyclin-dependent kinase-like 5 (CDKL5) gene, which encodes a serine/threonine protein kinase, can cause the CDKL5 deficiency disorder (CDD), a severe neurodevelopmental disease characterized by epileptic encephalopathy and neurocognitive impairment. The CDKL5 kinase consists of a catalytic N-terminal domain (NTD) and a less characterized C-terminal domain (CTD). Numerous disease-related mutations truncate CDKL5, leaving the NTD intact while variably shortening the CTD, which highlights the importance of the CTD for CDKL5 function. By systematically analyzing CDKL5 compositional features and evolutionary dynamics, we found that the CTD is a low-complexity region (LCR) highly enriched in serine residues and with a high propensity to undergo liquid-liquid phase separation (LLPS), a biophysical process of condensation controlling protein localization and function. Using a combination of super-resolution imaging, electron microscopy, and molecular and cellular approaches, including optogenetic LLPS induction, we discovered that CDKL5 undergoes LLPS, predominantly driven by its CTD, forming membraneless condensates in neuronal and non-neuronal cells. A CTD internal fragment (CTIF) plays a pivotal LLPS-promoting role, along with the distal portion of the protein. Indeed, two disease-related truncating mutations (S726X and R781X), eliding variable portions of the CTIF, significantly impair LLPS. This impairment is paralleled at the functional level by a reduction in the CDKL5-dependent phosphorylation of EB2, a known CDKL5 target. These findings demonstrate that CDKL5 undergoes LLPS, driven by a CTD region elided by most disease-related truncating mutations. Its loss––through the impairment of CDKL5 LLPS and functional activity––may play a key role in the molecular pathogenesis of CDD.

Abstract: Gene delivery is fundamentally crucial for the genetic manipulation of stem cells. Here, we present a straightforward approach to create a library of charge-neutralized polyethylenimine (PEI)-lipid nanoparticles designed for stem cell transfection. These lipid nanoparticles were formulated using small, branched PEI and lipidic anhydrides. Remarkably, over 15% of the lipid nanoparticles demonstrated high transfection efficiency across various cell types, surpassing the efficiency of both Lipofectamine 2000 and FuGENE HD. A structure-activity analysis indicated that the length and ratio of hydrophobic alkyl substitutions were critical parameters for efficient gene delivery. Notably, the transfection efficiency was higher than that of the original cation PEI. Our optimized PEI-lipid system enabled highly effective plasmid DNA delivery and successfully co-transferred two plasmid DNAs into difficult-to-transfect human embryonic stem cells (hESCs), facilitating optogenetic manipulation within these cells.

Abstract: Collective cell migration is key during development, wound healing, and metastasis and relies on coordinated cell behaviors at the group level. Src kinase is a key signalling protein for the physiological functions of epithelia, as it regulates many cellular processes, including adhesion, motility, and mechanotransduction. Its overactivation is associated with cancer aggressiveness. Here, we take advantage of optogenetics to precisely control Src activation in time and show that its pathological-like activation slows the collective rotation of epithelial cells confined into circular adhesive patches. We interpret velocity, force, and stress data during period of non-activation and period of activation of Src thanks to a hydrodynamic description of the cell assembly as a polar active fluid. Src activation leads to a 2-fold decrease in the ratio of polar angle to friction, which could result from increased adhesiveness at the cell-substrate interface. Measuring internal stress allows us to show that active stresses are subdominant compared to traction forces. Our work reveals the importance of fine-tuning the level of Src activity for coordinated collective behaviors.

Abstract: The post-translational modification of intracellular proteins through O-linked β-N-acetylglucosamine (O-GlcNAc) is a conserved regulatory mechanism in multicellular organisms. Catalyzed by O-GlcNAc transferase (OGT), this dynamic modification has an essential role in signal transduction, gene expression, organelle function and systemic physiology. Here, we present Opto-OGT, an optogenetic probe that allows for precise spatiotemporal control of OGT activity through light stimulation. By fusing a photosensitive cryptochrome protein to OGT, Opto-OGT can be robustly and reversibly activated with high temporal resolution by blue light and exhibits minimal background activity without illumination. Transient activation of Opto-OGT results in mTORC activation and AMPK suppression, which recapitulate nutrient-sensing signaling. Furthermore, Opto-OGT can be customized to localize to specific subcellular sites. By targeting OGT to the plasma membrane, we demonstrate the downregulation of site-specific AKT phosphorylation and signaling outputs in response to insulin stimulation. Thus, Opto-OGT is a powerful tool for defining the role of O-GlcNAcylation in cell signaling and physiology.

Abstract: Epithelia are polarized layers of cells that line the outer and inner surfaces of organs. At the basal side, the epithelial cell layer is supported by a basement membrane, which is a thin polymeric layer of self-assembled extracellular matrix (ECM) that tightly adheres to the basal cell surface. Proper shaping of epithelial layers is an important prerequisite for the development of healthy organs during the morphogenesis of an organism. Experimental evidence suggests that local degradation of the basement membrane is one of the mechanisms that can drive epithelial folding. However, how folding emerges in the absence of tissue growth remains elusive. Here, we present a coarse-grained plate theory model of the basement membrane that assumes force balance between i) cell-transduced active forces and ii) deformation-induced elastic forces. We verify key assumptions of this model through experiments in the Drosophila wing disc epithelium and demonstrate that the model can explain the emergence of outward epithelial folds upon local plate degradation. The model accounts for local degradation of the basement membrane as a mechanism for the generation of epithelial folds in the absence of epithelial growth.

Abstract: Hsp70 prevents protein aggregation and is cytoprotective, but sustained Hsp70 overexpression is problematic. Therefore, we characterized small molecule agonists that augment Hsp70 activity. Because cumbersome assays were required to assay agonists, we developed cell-based and in vivo assays in which disease-associated consequences of Hsp70 activation can be quantified. One assay uses an optogenetic system in which the formation of TDP-43 inclusions can be controlled, and the second assay employs a zebrafish model for acute kidney injury (AKI). These complementary assays will facilitate future work to identify new Hsp70 agonists as well as optimized agonist derivatives.

Abstract: Dysfunction of the RNA binding protein heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) contributes to neurodegeneration, the primary cause of permanent disability in multiple sclerosis (MS). To better understand the role of hnRNP A1 dysfunction in the pathogenesis of neurodegeneration, we utilized optogenetics-driven hnRNP A1 clustering to model its dysfunction in neuron-like differentiated Neuro-2A cells. hnRNP A1 clustering activates the integrated stress response (ISR) and results in a neurodegenerative phenotype marked by decreased neuronal protein translation and neurite loss. Small molecule inhibition of the ISR with either PERKi (GSK2606414) or ISRIB (integrated stress response inhibitor) attenuated both the decrease in neuronal translation and neurite loss, without affecting hnRNP A1 clustering. We then confirmed a strong association between hnRNP A1 clustering and ISR activation in neurons from MS brains. These data illustrate that hnRNP A1 dysfunction promotes neurodegeneration by activation of the ISR in vitro and in vivo, thus revealing a novel therapeutic target to reduce neurodegeneration and subsequent disability in MS.

Abstract: Biomolecular condensates (BMCs), play significant roles in organizing cellular functions in the absence of membranes through phase separation events involving RNA, proteins, and RNA-protein complexes. These membrane-less organelles form dynamic multivalent weak interactions, often involving intrinsically disordered proteins or regions (IDPs/IDRs). However, the nature of these crucial interactions, how most of these organelles are organized and are functional, remains unknown. Aberrant condensates have been implicated in neurodegenerative diseases and various cancers, presenting novel therapeutic opportunities for small molecule condensate modulators. Recent advancements in optogenetic technologies, particularly Corelet, enable precise manipulation of BMC dynamics within living cells, facilitating high-throughput screening for small molecules that target these complex structures. By elucidating the molecular mechanisms governing BMC formation and function, this innovative approach holds promise to unlock therapeutic strategies against previously "undruggable" protein targets, paving the way for effective interventions in disease.

Abstract: Alternative splicing is a fundamental process that contributes to the functional diversity and complexity of proteins. The regulation of each alternative splicing event involves the coordinated action of multiple RNA-binding proteins, creating a diverse array of alternatively spliced products. Dysregulation of alternative splicing is associated with various diseases, including neurodegeneration. Here we demonstrate that CELF2, a splicing regulator and a GWAS-identified risk factor for Alzheimer’s disease, binds to mRNAs associated with neurodegenerative diseases, with a specific interaction observed in the intron adjacent to exon 10 on Tau mRNA. Loss of CELF2 in the mouse brain results in a decreased inclusion of Tau exon 10, leading to a reduced 4R:3R ratio. Further exploration shows that the hinge domain of CELF2 possesses an intrinsically disordered region (IDR), which mediates CELF2 condensation and function. The functionality of IDR in regulating CELF2 function is underscored by its substitutability with IDRs from FUS and TAF15. Using TurboID we identified proteins that interact with CELF2 through its IDR. We revealed that CELF2 co-condensate with NOVA2 and SFPQ, which coordinate with CELF2 to regulate the alternative splicing of Tau exon 10. A negatively charged residue within the IDR (D388), which is conserved among CELF proteins, is critical for CELF2 condensate formation, interactions with NOVA2 and SFPQ, and function in regulating tau exon 10 splicing. Our data allow us to propose that CELF2 regulates Tau alternative splicing by forming condensates through its IDR with other splicing factors, and that the composition of the proteins within the condensates determines the outcomes of alternative splicing events.

Abstract: Cells use signalling pathways as windows into the environment to gather information, transduce it into their interior, and use it to drive behaviours. MAPK (ERK) is a highly conserved signalling pathway in eukaryotes, directing multiple fundamental cellular behaviours such as proliferation, migration, and differentiation, making it of few central hubs in the signalling circuitry of cells. Despite this versatility of behaviors, population-level measurements have reported low information content (< 1 bit) relayed through the ERK pathway, rendering the population barely able to distinguish the presence or absence of stimuli. Here, we contrast the information transmitted by a single cell and a population of cells. Using a combination of optogenetic experiments, data analysis based on information theory framework, and numerical simulations we quantify the amount of information transduced from the receptor to ERK, from responses to singular, brief and sparse input pulses. We show that single cells are indeed able to resolve between graded stimuli, yielding over 2 bit of information, however showing a large population heterogeneity

Abstract: Biomolecular condensates appear throughout cell physiology and pathology, but the specific role of condensation or its dynamics is often difficult to determine. Optogenetics offers an expanding toolset to address these challenges, providing tools to directly control condensation of arbitrary proteins with precision over their formation, dissolution, and patterning in space and time. In this review, we describe the current state of the field for optogenetic control of condensation. We survey the proteins and their derivatives that form the foundation of this toolset, and we discuss the factors that distinguish them to enable appropriate selection for a given application. We also describe recent examples of the ways in which optogenetic condensation has been used in both basic and applied studies. Finally, we discuss important design considerations when engineering new proteins for optogenetic condensation, and we preview future innovations that will further empower this toolset in the coming years.

Abstract: Alpha-synuclein (α-syn) aggregation is a defining feature of Parkinson's disease (PD) and related synucleinopathies. Despite significant research efforts focused on understanding α-syn aggregation mechanisms, the early stages of this process remain elusive, largely due to limitations in experimental tools that lack the temporal resolution to capture these dynamic events. Here, we introduce UltraID-LIPA, an innovative platform that combines the Light-Inducible Protein Aggregation (LIPA) system with the UltraID proximity-dependent biotinylation assay to identify α-syn-interacting proteins and uncover key mechanisms driving its oligomerization. UltraID-LIPA successfully identified 38 α-syn-interacting proteins, including both established and novel candidates, highlighting the accuracy and robustness of the approach. Notably, a strong interaction with endolysosomal and membrane-associated proteins was observed, supporting the hypothesis that interactions with membrane-bound organelles are pivotal in the early stages of α-syn aggregation. This powerful platform provides new insights into dynamic protein aggregation events, enhancing our understanding of synucleinopathies and other proteinopathies.

Abstract: Synucleinopathies, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are triggered by α-synuclein aggregation, triggering progressive neurodegeneration. However, the intracellular α-synuclein aggregation mechanism remains unclear. Herein, we demonstrate that RNA G-quadruplex assembly forms scaffolds for α-synuclein aggregation, contributing to neurodegeneration. Purified α-synuclein binds RNA G-quadruplexes directly through the N terminus. RNA G-quadruplexes undergo Ca2+-induced phase separation and assembly, accelerating α-synuclein sol-gel phase transition. In α-synuclein preformed fibril-treated neurons, RNA G-quadruplex assembly comprising synaptic mRNAs co-aggregates with α-synuclein upon excess cytoplasmic Ca2+ influx, eliciting synaptic dysfunction. Forced RNA G-quadruplex assembly using an optogenetic approach evokes α-synuclein aggregation, causing neuronal dysfunction and neurodegeneration. The administration of 5-aminolevulinic acid, a protoporphyrin IX prodrug, prevents RNA G-quadruplex phase separation, thereby attenuating α-synuclein aggregation, neurodegeneration, and progressive motor deficits in α-synuclein preformed fibril-injected synucleinopathic mice. Therefore, Ca2+ influx-induced RNA G-quadruplex assembly accelerates α-synuclein phase transition and aggregation, potentially contributing to synucleinopathies.

Abstract: Intracellular trafficking, an extremely complex network, dynamically orchestrates nearly all cellular activities. A versatile method that enables the manipulation of target transport pathways with high spatiotemporal accuracy in vitro and in vivo is required to study how this network coordinates its functions. Here, a new method called RIVET (Rapid Immobilization of target Vesicles on Engaged Tracks) is presented. Utilizing inducible dimerization between target vesicles and selective cytoskeletons, RIVET can spatiotemporally halt numerous intracellular trafficking pathways within seconds in a reversible manner. Its highly specific perturbations allow for the real-time dissection of the dynamic relationships among different trafficking pathways. Moreover, RIVET is capable of inhibiting receptor-mediated endocytosis. This versatile system can be applied from the cellular level to whole organisms. RIVET opens up new avenues for studying intracellular trafficking under various physiological and pathological conditions and offers potential strategies for treating trafficking-related disorders.

Abstract: Centrosomes ensure accurate chromosome segregation during cell division. Although the regulation of centrosome number is well-established, less is known about the suppression of non-centrosomal MTOCs (ncMTOCs). The E3 ligase TRIM37, implicated in Mulibrey nanism and 17q23-amplified cancers, has emerged as a key regulator of both centrosomes and ncMTOCs. Yet, the mechanism by which TRIM37 achieves enzymatic activation to target these mesoscale structures had remained unknown. Here, we elucidate TRIM37’s activation process, beginning with TRAF domain-directed substrate recognition, progressing through B-box domain-mediated oligomerization, and culminating in RING domain dimerization. Using optogenetics, we demonstrate that TRIM37’s E3 activity is directly coupled to the assembly state of its substrates, activating only when centrosomal proteins cluster into higher-order assemblies resembling MTOCs. This regulatory framework provides a mechanistic basis for understanding TRIM37-driven pathologies and, by echoing TRIM5’s restriction of the HIV capsid, unveils a conserved activation blueprint among TRIM proteins for controlling mesoscale assembly turnover.

Abstract: Mitochondria provide cells with energy and regulate the cellular metabolism. Almost all mitochondrial proteins are nuclear-encoded, translated on ribosomes in the cytoplasm, and subsequently transferred to the different subcellular compartments of mitochondria. Here, we developed OptoMitoImport, an optogenetic tool to control the import of proteins into the mitochondrial matrix via the presequence pathway on demand. OptoMitoImport is based on a two-step process: first, light-induced cleavage by a TEV protease cuts off a plasma membrane-anchored fusion construct in close proximity to a mitochondrial targeting sequence; second, the mitochondrial targeting sequence preceding the protein of interest recruits to the outer mitochondrial membrane and imports the protein fused to it into mitochondria. Upon reaching the mitochondrial matrix, the matrix processing peptidase cuts off the mitochondrial targeting sequence and releases the protein of interest. OptoMitoImport is available as a two-plasmid system as well as a P2A peptide or IRES sequence-based bicistronic system. Fluorescence studies demonstrate the release of the plasma membrane-anchored protein of interest through light-induced TEV protease cleavage and its localization to mitochondria. Cell fractionation experiments confirm the presence of the peptidase-cleaved protein of interest in the mitochondrial fraction. The processed product is protected from proteinase K treatment. Depletion of the membrane potential across the inner mitochondria membrane prevents the mitochondrial protein import, indicating an import of the protein of interest by the presequence pathway. These data demonstrate the functionality of OptoMitoImport as a generic system with which to control the post-translational mitochondrial import of proteins via the presequence pathway.

Abstract: When mammalian cells are exposed to extracellular stress, they coordinate the condensation of stress granules (SGs) through the action of key nucleating proteins G3BP1 and G3BP2 (G3BPs) and, simultaneously, undergo a massive reduction in translation.1-5 Although SGs and G3BPs have been linked to this translation response, their overall impact has been unclear. Here, we investigate the longstanding question of how, and indeed whether, G3BPs and SGs shape the stress translation response. We find that SGs are enriched for mRNAs that are resistant to the stress-induced translation shutdown. Although the accurate recruitment of these stress-resistant mRNAs does require the context of stress, a combination of optogenetic tools and spike-normalized ribosome profiling demonstrates that G3BPs and SGs are necessary and sufficient to both help prioritize the translation of their enriched mRNAs and help suppress cytosolic translation. Together these results support a model in which G3BPs and SGs reinforce the stress translation program by prioritizing the translation of their resident mRNAs.

Abstract: Immediately after fertilization the genome is transcriptionally quiescent. Maternally encoded pioneer transcription factors reprogram the chromatin state and facilitate the transcription of the zygotic genome. In Drosophila, transcription is initiated by the pioneer factor Zelda. While Zelda-occupied sites are enriched with histone acetylation, a post-translational mark associated with active cis-regulatory regions, the functional relationship between Zelda and histone acetylation in zygotic genome activation remained unclear. We show that Zelda-mediated recruitment of the histone acetyltransferase CBP is essential for zygotic transcription. CBP catalytic activity is necessary for release of RNA Polymerase II (Pol II) into transcription elongation and for embryonic development. However, CBP also activates zygotic transcription independent of acetylation through Pol II recruitment. Neither acetylation nor CBP are required for the pioneering function of Zelda. Our data suggest that pioneer factor-mediated recruitment of CBP is a conserved mechanism required to activate zygotic transcription but that this role is separable from the function of pioneer factors in restructuring chromatin accessibility.

Abstract: Cell contacts in epithelia are remodeled to regulate paracellular permeability and to control passage of migrating cells, but how barrier function is modulated while preserving epithelial integrity is not clear. In the follicular epithelium of Drosophila ovaries, tricellular junctions (TCJs) open transiently in a process termed patency to allow passage of externally produced yolk proteins for uptake by the oocyte. Here we show that modulation of actomyosin contractility at cell vertices controls TCJ permeability. Before patency, circumferential actomyosin bundles are anchored at apical follicle cell vertices, where tension-sensing junctional proteins, Rho-associated kinase (Rok), and active Myosin II accumulate and maintain vertices closed. TCJ opening is initiated by redistribution of Myosin II from circumferential bundles to a medial pool, accompanied by decreasing tension on vertices. This transition requires activation of Cofilin-dependent F-actin disassembly by the phosphatase Slingshot and Myosin II inactivation by Myosin light chain phosphatase, and is counteracted by Rok. Accordingly, constitutive activation of Myosin or of Rho signaling prevent vertex opening, whereas reduced Myosin II or Rok activity cause excessive and premature vertex opening. Thus, opening of intercellular gaps in the follicular epithelium does not require actomyosin-based forces, but relies on a reduction of actomyosin contractility. Conversely, F-actin assembly is required for closing intercellular gaps after patency. Our findings are consistent with a force transduction model in which TCJ integrity is maintained by vertex-anchored contractile actomyosin. We propose that the cell-type-specific organization of actomyosin at cell vertices determines the mode of contractility-dependent regulation of epithelial permeability.

Abstract: RNA molecules play a vital role in linking genetic information with various cellular processes. In recent years, a variety of optogenetic tools have been engineered for regulating cellular RNA metabolism and functions. These highly desirable tools can offer non-intrusive control with spatial precision, remote operation, and biocompatibility. Here, we would like to review these currently available approaches that can regulate RNAs with light: from non-genetically encodable chemically modified oligonucleotides to genetically encoded RNA aptamers that recognize photosensitive small-molecule or protein ligands. Some key applications of these optogenetic tools will also be highlighted to illustrate how they have been used for regulating all aspects of the RNA life cycle: from RNA synthesis, maturation, modification, and translation to their degradation, localization, and phase separation control. Some current challenges and potential practical utilizations of these RNA optogenetic tools will also be discussed.