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1.
An optogenetic smart microscopy platform reveals signaling dynamics-dependent control over collective cell migration.
Abstract:
In cell biology, optical techniques can measure cells' internal states (biosensors) and stimulate cellular responses (optogenetics). Yet the design of all-optical experiments is often manual: a predetermined stimulus pattern is applied to cells, biosensors are measured over time, and data are processed offline. Here, we develop PyCLM, a Python-based suite enabling closed-loop measurement, image segmentation, and optogenetic control of thousands of cells per experiment. We showcase PyCLM on diverse applications, including performing feedback control on single cells and delivering developmental signaling patterns to Drosophila embryos. We compare single-cell versus tissue-scale optogenetic control of epithelial migration, revealing that fast and slow waves of receptor tyrosine kinase activity determine the direction of tissue movement, matching prior in vivo observations in zebrafish and mouse. PyCLM enables simple setup of dynamic experiments to probe cell and tissue properties and provides a first step toward real-time control of single-cell states at the tissue scale.
2.
CD44 restricts EGFR mobility to polarize cytoskeletal signalling modules driving bleb-based migration.
Abstract:
Cells under high confinement migrate efficiently in low-adhesion environments by forming stable, polarized, hydrostatic pressure-driven leader blebs. Here we investigated the basis of polarized bleb morphology in metastatic melanoma cells migrating under low-adhesive and highly confined microenvironments. Using high-resolution live imaging, molecular perturbations and biosensors, we show that EGF signalling through PI3K stabilizes and maintains polarized leader blebs. EGFR and PI3K activities form a gradient within leader blebs that decreases from rear to front, promoting phosphatidylinositol 3,4,5-trisphosphate and Rac1-GTP accumulation at the bleb rear, whereas phosphatidylinositol 4,5-bisphosphate and RhoA-GTP concentrate at the bleb tip, the inverse of the organization observed in integrin-dependent mesenchymal migration. Optogenetic disruption of this gradient triggers bleb retraction, underscoring its functional importance. Mathematical modelling and experiments identified a mechanism whereby during bleb initiation, CD44 and ERM proteins restrict EGFR mobility within a membrane-apposed cortical actin meshwork at the bleb rear, establishing the EGFR-PI3K-Rac gradient. Together, these findings define the biophysical and molecular mechanisms that underlie polarity in bleb-based migration and highlight how alternative spatial organization of signalling modules supports distinct migration modes in different microenvironments.
3.
Mapping the GDF15 arm of the integrated stress response in human cells and tissues.
Abstract:
Mitochondrial stress activates the integrated stress response (ISR) and triggers cell-cell communication through the secretion of the metabokine growth differentiation factor 15 (GDF15). However, the gene network underlying the ISR remains poorly defined across metabolically diverse cellular states and tissues. Using RNAseq data from fibroblasts subjected to eleven metabolic perturbations, including genetic and pharmacological mitochondrial OxPhos defects, we show that the ISR has multiple arms. To quantify the GDF15 arm of ISR activation in human cells, we developed an ISRGDF15 index. We validate the ISRGDF15 index in datasets from optogenetic and small molecule activation of ISR kinases, demonstrating its rapid kinetics preceding to GDF15 gene expression. We then deploy the ISRGDF15 index across 44 postmortem human tissues, confirm its correlation with age, and report that the ISRGDF15 is upregulated in the heart of individuals with acute causes of death in the emergency room, whereas it was upregulated in the brain of individuals who died after protracted hospital inpatient stays. These data highlight distinct arms of the ISR and clarify genes related to the GDF15 ISR arm, yielding an ISRGDF15 index that can be used to investigate tissue-specific and age-related ISR activation in both in vitro cultures and human tissues.
4.
Short RNA chaperones promote aggregation-resistant TDP-43 conformers to mitigate neurodegeneration.
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Copley, KE
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Mauna, JC
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Danielson, HL
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Chen, Q
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Ozguney, B
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Ngo, M
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Xie, L
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Smirnov, A
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Davis, M
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Mayne, L
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Linsenmeier, M
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Rubien, JD
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Bergmann, CA
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Portz, B
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Lee, BL
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Odeh, HM
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Lai, L
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Chang, YW
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Hallegger, M
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Ule, J
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Pasinelli, P
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Poon, Y
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Mittal, J
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Fawzi, NL
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Black, BE
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Donnelly, CJ
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Jensen, BK
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Shorter, J
Abstract:
Aberrant aggregation of the prion-like RNA binding protein TDP-43 drives several fatal neurodegenerative proteinopathies, including amyotrophic lateral sclerosis (ALS). In this work, we define how short, specific RNAs solubilize TDP-43. These short RNAs engage and stabilize the TDP-43 RNA recognition motifs, which allosterically destabilizes a conserved helical region in the prion-like domain, thereby promoting aggregation-resistant conformers. Sequence-space mining identified short RNA chaperones with enhanced activity against TDP-43 and disease-linked variants. Enhanced short RNA chaperones mitigated aberrant TDP-43 phenotypes in optogenetic models and in ALS patient-derived and control motor neurons. In mice with cytoplasmic TDP-43 aggregation and motor neuron loss, an enhanced short RNA chaperone reduced pathological aggregation, restored TDP-43 function, and conferred neuroprotection. These results define a mechanistic and therapeutic framework for RNA-based strategies to counter TDP-43 proteinopathies.
5.
BMAL1 regulates circadian rhythms via phase separation-mediated transcriptional hub formation.
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Gao, W
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Zhu, L
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Wei, Y
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Luo, G
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Wang, J
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Wang, L
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Peng, Z
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Li, X
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Wu, Z
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Li, J
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Wu, Y
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Wang, X
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Jing, J
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Zou, S
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Zhao, Q
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Fan, Y
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Yuan, Q
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Zhou, C
Abstract:
The mechanisms by which core clock components are spatially organized to ensure robust oscillations in mammals remain unclear. Here, we identify the positive limb factor BMAL1 as a phase-separating protein that forms dynamic biomolecular condensates essential for circadian transcription and behavior. Endogenous BMAL1 forms nuclear puncta that oscillate in sync with the circadian cycle. Deletion analysis and optogenetic clustering identify an N-terminal 90-amino acid intrinsically disordered region whose phosphorylation state tunes BMAL1 phase separation. Besides, BMAL1 condensates behave as multi-molecular assemblies that selectively recruit CLOCK, p300, MED1, and are specifically promoted by E-box DNA. Functionally, an IDR-deleted BMAL1 mutant fails to rescue rhythmic transcription in Bmal1-KO cells and cannot restore locomotor rhythms when reintroduced into SCN-specific Bmal1‑KO mice. These findings establish BMAL1 condensates as dynamic transcriptional hubs that couple phase separation to circadian rhythm in cells and in vivo.
6.
Membranes arrest the coarsening of mitochondrial condensates in human cells.
Abstract:
Mitochondria contain double membranes that enclose their contents. Within their interior, the mitochondrial genome and its RNA products are condensed into ~100 nm sized (ribo)nucleoprotein complexes. How these endogenous condensates maintain their roughly uniform size and spatial distributions within mitochondria remains unclear. Here, we engineer optogenetic tools (mt-optoIDR) that enable controlled formation of synthetic condensates within live mitochondria upon light activation in HeLa cells. Using high-resolution microscopy, we visualize the nucleation of small, yet elongated condensates (mt-opto-condensates), which recapitulate the morphologies of endogenous mt-condensates. These narrow size distributions are independent of mt-optoIDR sequence features, suggesting the mitochondrial environment influences condensate formation. Consistently, mt-opto-condensates fluctuate within voids in between cristae in tubular mitochondria. To directly isolate the contribution of the mitochondrial membranes, we overexpress the dominant negative membrane fusion mutant (Drp1K38A), which results in the formation of bulbous mitochondria with restructured cristae. Based on quantitative particle tracking, bulbous mitochondria support significantly increased dynamics and rapid coarsening of mt-opto-condensates into a single, prominent droplet-in contrast to the membrane confinement observed in tubular mitochondria. Together, these observations inform how membranes can constrain the growth and dynamics of the condensates they enclose, without the need for additional regulatory mechanisms.
7.
Tau oligomerization induces nuclear lamina invagination and chromatin remodeling in Alzheimer's disease.
Abstract:
The aggregation of the microtubule-associated protein tau into oligomeric complexes is strongly correlated with the onset and progression of neurodegeneration in Alzheimer's disease (AD). Increasing evidence implicates nuclear membrane disruption in AD and related tauopathies; however, whether this is a cause or consequence of neurodegeneration remains unresolved. Here, we show that nuclear lamina disruption emerges at the early Braak stages, coinciding with the initial formation of pathological tau aggregates in post-mortem AD brain tissue. Using the tauopathy mouse model (P301S PS19), we demonstrate that oligomeric tau (oTau) directly binds to the Lamin B Receptor (LBR), inducing nuclear envelope invaginations as revealed by electron microscopy. These structural alterations are accompanied by chromatin remodeling and gene expression dysregulation. To dissect the underlying mechanism, we employed a light-inducible OptoTau system (4R1N Tau::mCherry::Cry2Olig) in human iPSC-derived neurons, enabling real-time visualization of tau aggregation dynamics. This system revealed selective recruitment of oTau to the nuclear envelope and direct interactions with LBR and Lamin B2, leading to nuclear deformation and activation of the protein translational stress response. Together, these findings identify nuclear membrane disruption as an early and potentially causative event in tau-mediated neurodegeneration, establishing a mechanistic link between tau oligomerization, nuclear stress, and chromatin remodeling. Targeting nuclear destabilization may offer new therapeutic avenues for mitigating AD pathogenesis.
8.
WDR44 drives de novo α-synuclein aggregation at the lysosomal membrane and promotes neuronal dysfunction in Parkinson's Disease.
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Teixeira, M
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Sheta, R
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Bérard, M
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Insinna, C
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Mahul-Mellier, AL
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Delmas, CVL
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Lépinay, E
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Idi, W
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Ricard, A
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Del Cid-Pellitero, E
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Trabolsi, C
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Gobeil, S
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Canron, MH
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Bézard, E
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Rajput, A
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Cicchetti, F
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Parent, M
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Fon, EA
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Ramalingam, N
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Dettmer, U
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Calon, F
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Westlake, C
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Lashuel, HA
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Oueslati, A
Abstract:
The aggregation of α-synuclein (α-SYN) into Lewy bodies (LBs) is a central event in the pathogenesis of Parkinson's disease (PD) and related synucleinopathies1,2. Despite significant advances in understanding α-SYN self-assembly, the precise sequence of early aggregation steps has not been directly visualized in living neurons. Here, we use an optogenetic-induced protein aggregation system with a high temporal resolution to monitor the onset of α-SYN assembly in neurons. We found that the initiation and accumulation of α-SYN aggregates occur predominantly at the lysosomal membrane, an event driven by the α-SYN N-terminus and modulated by the membrane-associated adaptor protein WD repeat-containing protein 44 (WDR44). Remarkably, we demonstrate that WDR44 knockdown markedly reduced de novo α-SYN aggregation in both neuronal cultures and in vivo, whereas WDR44 overexpression enhances α-SYN aggregation in PD patient-derived iPSC neurons. Consistent with its potential pathogenic involvement, WDR44 aberrantly accumulates in vivo and in the brains of PD patients, where it colocalizes with LB inclusions. Finally, we show that lysosome-associated α-SYN aggregates compromised lysosomal structure and function, leading to neuronal impairment, a phenotype worsened by WDR44 overexpression, linking early aggregation events to downstream toxicity. Together, these findings reveal the earliest dynamic stages of α-SYN oligomerization in living neurons and identify the WDR44-α-SYN interaction as a promising therapeutic target for reducing α-SYN pathology and enabling early intervention in PD.
9.
Optogenetic Control of the Integrated Stress Response Limits Glioblastoma Invasion.
Abstract:
The integrated stress response (ISR) is a highly conserved signaling network, allowing cells to adapt and respond to various stressors. With its aggressive spread and high recurrence rates, glioblastoma multiforme (GBM) is one of the toughest cancers to date, yet the role of the ISR is still to be well understood, whether activation may suppress or promote this disease, and drug-treatment of GBM has thus far shown inconclusive results. In this work, we use an optogenetic tool, opto-PKR, to specifically trigger ISR activation via light-induced oligomerizing PKR-kinases, offering high spatiotemporal and reversible control, while avoiding potential upstream damage or side effects from drugs. Using immunofluorescence and RNA-sequencing, we show that targeted ISR activation reaching levels where both adaptive (ATF4) and terminal responses (CHOP) are activated results in subsequent downregulation of genes associated with the extracellular environment and glial cell migration, further supported by ECM-stain and scratch assays. Next, we show inhibition of aggressive spread for ISR-activated GBM spheroids in collagen 3D culture. Photopatterning of ISR activation in spheroids demonstrates a cell-intrinsic effect at the tissue scale, and recovery studies indicate a tunable, non-ablative intervention space. These findings suggest a route to containment and motivate ISR-activating small molecule screening in GBM models.
10.
OptoLoop - an optogenetic tool to probe the functional role of genome organization.
Abstract:
The genome folds inside the cell nucleus into hierarchical architectural features, such as chromatin loops and domains. If and how this genome organization influences the regulation of gene expression remains only partially understood. The structure-function relationship of genomes has traditionally been probed by population-wide measurements after mutation of crucial DNA elements or by perturbation of chromatin-associated proteins. To circumvent possible pleiotropic effects of such approaches, we have developed OptoLoop, an optogenetic system that allows direct manipulation of chromatin contacts by light in a controlled fashion. OptoLoop is based on the fusion between a nuclease-dead SpCas9 protein and the light-inducible oligomerizing protein CRY2. We demonstrate that OptoLoop can bring together genomically distant, repetitive DNA loci. As a proof-of-principle application of OptoLoop, we probed the functional role of DNA looping in the regulation of the human telomerase gene TERT. By analyzing the extent of chromatin looping and nascent RNA production at individual alleles, we find evidence for looping-mediated repression of TERT. In sum, OptoLoop represents a novel means for the interrogation of structure-function relationships in the genome.
11.
Optogenetic Translocation to Subcellular Compartments through Regulation of Protein Avidity.
Abstract:
Inducible translocation to subcellular compartments is a common strategy for protein switches that control a variety of cell behaviors. However, existing switches achieve translocation through induced dimerization, requiring constitutive anchoring of one component into the target compartment and optimization of relative expression levels between the two components. We present a simpler, single-component strategy called Avidity-assisted targeting (Aviatar). Aviatar achieves translocation with only a single protein by converting low-affinity monomers into high-avidity assemblies through inducible clustering. We demonstrated the Aviatar concept and its generality using optogenetic clustering to drive translocation to the plasma membrane, endosomes, golgi, endoplasmic reticulum, and microtubules using binding domains for lipids or endogenous proteins that were specific to those compartments. Aviatar recruitment regulated actin polymerization at the cell periphery and revealed compartment-specific signaling of receptor tyrosine kinase fusions associated with cancer. Finally, GFP-targeting Aviatar probes allowed inducible localization to any GFP-tagged target, including endogenously tagged stress granule proteins. Aviatar is a straightforward platform that can be rapidly adapted to a broad array of targets without the need for their prior modification or disruption.
12.
Defining RNA oligonucleotides that reverse deleterious phase transitions of RNA-binding proteins with prion-like domains.
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Guo, L
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Mann, JR
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Mauna, JC
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Copley, KE
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Wang, H
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Rubien, JD
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Bergmann, CA
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Carey, JL
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Merjane, J
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Ngo, M
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Xu, J
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Odeh, HM
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Lin, J
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Lee, BL
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Ganser, L
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Robinson, E
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Kim, KM
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Murthy, AC
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Paul, T
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Portz, B
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Gleixner, AM
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Diaz, Z
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Smirnov, A
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Padilla, G
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Lavorando, E
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Espy, C
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Shang, Y
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Huang, EJ
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Chesi, A
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Fawzi, NL
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Myong, S
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Donnelly, CJ
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Shorter, J
Abstract:
RNA-binding proteins (RBPs) with prion-like domains (PrLDs), such as FUS and TDP-43, condense into functional liquids, which can transform into pathological fibrils that underpin fatal neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD). Here, we define short RNAs that prevent FUS fibrillization by promoting liquid phases and distinct short RNAs that prevent and reverse FUS condensation and fibrillization. These activities require interactions with multiple RNA-binding domains of FUS and are encoded by RNA sequence, length, and structure. We define a short RNA that dissolves cytoplasmic FUS aggregates, restores nuclear FUS, and mitigates FUS toxicity in optogenetic models and ALS patient-derived motor neurons. Another short RNA dissolves cytoplasmic TDP-43 aggregates, restores nuclear TDP-43, and mitigates TDP-43 toxicity. Since short RNAs can be effectively delivered to the human brain, these oligonucleotides could have utility for ALS/FTD and related disorders.
13.
Protocol for dissecting the aggregation-prone protein interactome with optogenetic-induced aggregation and biotin labeling proximity assay.
Abstract:
The dynamics of the early steps of protein aggregation remain poorly understood, particularly in the case of α-synuclein (α-syn) aggregation, the hallmark of synucleinopathies. Here, we present a protocol that combines light-inducible protein aggregation (LIPA) with proximity biotinylation using an UltraID construct. We describe the workflow from protein expression to biochemical validation, including the purification of biotinylated proteins prior to liquid chromatography-mass spectrometry (LC-MS) analysis and subsequent validation. This platform provides a powerful strategy to identify proteins interacting with nascent α-syn aggregates. For complete details on the use and execution of this protocol, please refer to Teixeira et al.1.
14.
Optogenetic-induced α-synuclein accumulation reveals early synaptic dysfunction in experimental models of Parkinson's disease.
Abstract:
Presynaptic accumulation of misfolded α-synuclein (α-syn) and altered synaptic transmission are considered early events in the pathogenesis of Parkinson's disease (PD), suggesting a potential causal link between these two events. However, the mechanisms by which α-syn aggregation induces synaptic dysfunction and the subsequent progressive neurodegeneration remain elusive. In the present study we leveraged the high temporal resolution of the Light-Inducible Protein Aggregation (LIPA) system in vivo and in human dopaminergic neurons to explore the early sequence of α-syn-induced pathological events leading to synaptopathy. We observed that nigrostriatal axonal transport and presynaptic accumulation of α-syn aggregates altered the activity of different neuronal populations in the mouse striatum. The results of histological and metabolite analyses show that presynaptic accumulation of α-syn induced a shift in the activation pattern of D1- and D2-expressing striatal medium spiny neurons, caused an increase in the size and density of dopaminergic synapses, and disrupted striatal dopamine signaling. Altogether, our findings reveal that the accumulation of α-syn in dopaminergic terminals triggered early presynaptic impairments, which subsequently altered striatal neuronal activity. Our study provides new insights into the molecular mechanisms underlying early synaptopathy in PD.
15.
Optogenetic Rescue Reveals Spatiotemporal Rules of Germ-Layer Patterning.
Abstract:
Embryonic cells must interpret morphogen signals that vary in both time and space, but the rules by which they decode these dynamics remain unclear. Here we combine optogenetics with human 2D gastruloids to define minimal WNT signaling rules for germ-layer patterning. We block endogenous WNT secretion to create a “blank canvas” and reconstitute signaling using light-gated LRP6. Systematic temporal scans reveal a narrow competence window when the onset and duration of WNT signaling specify mesoderm; this window is shifted by cell density and amplified by BMP priming, whereas identical WNT inputs outside it invert germ-layer order or generate alternative mesodermal subtypes. Using micromirror-based illumination, we restricted WNT activation to a mid-ring during this temporal window; combined with BMP4, this fully restored germ layer domains with boundaries sharper than those generated by ligand stimulation. Thus, precise spatiotemporal control of a single pathway is sufficient to optically rebuild germ-layer architecture and reveals WNT as a temporal morphogen.
16.
FLASH-AWAY: Intrabody-Directed Targeting of Optogenetic Tools for Protein Degradation.
Abstract:
Protein homeostasis, or proteostasis, is essential for cellular proteins to function properly. The buildup of abnormal proteins (such as damaged, misfolded, or aggregated proteins) is associated with many diseases, including cancer. Therefore, maintaining proteostasis is critical for cellular health. Currently, genetic methods for modulating proteostasis, such as RNA interference and CRISPR knockout, lack spatial and temporal precision. They are also not suitable for depleting already-synthesized proteins. Similarly, molecular tools like PROTACs and molecular glue face challenges in drug design and discovery. To directly control targeted protein degradation within cells, we introduce an intrabody-based optogenetic toolbox named Flash-Away. Flash-Away integrates the light-responsive ubiquitination activity of the RING domain of TRIM21 for protein degradation, coupled with specific intrabodies for precise targeting. Upon exposure to blue light, Flash-Away enables rapid and targeted degradation of selected proteins. This versatility is demonstrated through successful application to diverse protein targets, including actin, MLKL, and ALFA-tag fused proteins. This innovative light-inducible protein degradation system offers a powerful approach to investigate the functions of specific proteins within physiological contexts. Moreover, Flash-Away presents potential opportunities for clinical translational research and precise medical interventions, advancing the prospects of precision medicine.
17.
EGFR suppression and drug-induced potentiation are widespread features of oncogenic RTK fusions.
Abstract:
Regulation of cancer cells by their environment contributes to tumorigenesis and drug response, though the extent to which the oncogenic state can alter a cell's perception of its environment is not clear. Prior studies found that EML4-ALK, a receptor tyrosine kinase (RTK) fusion oncoprotein, suppresses transmembrane receptor signaling through EGFR. Moreover, suppression was reversed with targeted ALK inhibition, thereby promoting survival and drug tolerance. Here we tested whether such modulation of EGFR was common among other RTK fusions, which collectively are found in ∼5% of all cancers. Using live- and fixed-cell microscopy in isogenic and patient-derived cell lines, we found that a wide variety of RTK fusions suppress transmembrane EGFR and sequester essential adaptor proteins in the cytoplasm, as evidenced by the localization of endogenous Grb2. Targeted therapies rapidly released Grb2 from sequestration and potentiated EGFR. Synthetic optogenetic analogs of RTK fusions confirmed that cytoplasmic sequestration of Grb2 was sufficient to suppress perception of extracellular EGF and could do so without driving signaling from the synthetic fusion itself, demonstrating that fusion signaling and suppression of EGFR could be functionally decoupled. Our study uncovers that a large number of RTK fusions simultaneously act as both activators and suppressors of signaling, the mechanisms of which could be exploited for new biomimetic therapies that enhance cell killing and suppress drug tolerance.
18.
PyCLM: programming-free, closed-loop microscopy for real-time measurement, segmentation, and optogenetic stimulation.
Abstract:
In cell biology, optical techniques are increasingly used to measure cells' internal states (biosensors) and to stimulate cellular responses (optogenetics). Yet the design of all-optical experiments is often manual: a pre-determined stimulus pattern is applied to cells, biosensors are measured over time, and the resulting data is processed off-line. With the advent of machine learning for segmentation and tracking, it becomes possible to envision closed-loop experiments where real-time information about cells' positions and states are used to dynamically determine optogenetic stimuli to alter or control their behavior. Here, we develop PyCLM, a Python-based suite of tools to enable real-time measurement, image segmentation, and optogenetic control of thousands of cells per experiment. PyCLM is designed to be as simple for the end user as possible, and multipoint experiments can be set up that combine a wide variety of imaging, image processing, and stimulation modalities without any programming. We showcase PyCLM on diverse applications: studying the effect of epidermal growth factor receptor activity waves on epithelial tissue movement, simultaneously stimulating ~1,000 single cells to guide tissue flows, and performing real-time feedback control of cell-to-cell fluorescence heterogeneity. This tool will enable the next generation of dynamic experiments to probe cell and tissue properties, and provides a first step toward precise control of cell states at the tissue scale.
19.
Activation of NF-κB Signaling by Optogenetic Clustering of IKKα and β.
Abstract:
Molecular optogenetics allows the control of molecular signaling pathways in response to light. This enables the analysis of the kinetics of signal activation and propagation in a spatially and temporally resolved manner. A key strategy for such control is the light-inducible clustering of signaling molecules, which leads to their activation and subsequent downstream signaling. In this work, an optogenetic approach is developed for inducing graded clustering of different proteins that are fused to eGFP, a widely used protein tag. To this aim, an eGFP-specific nanobody is fused to Cryptochrome 2 variants engineered for different orders of cluster formation. This is exemplified by clustering eGFP-IKKα and eGFP-IKKβ, thereby achieving potent and reversible activation of NF-κB signaling. It is demonstrated that this approach can activate downstream signaling via the endogenous NF-κB pathway and is thereby capable of activating both an NF-κB-responsive reporter construct as well as endogenous NF-κB-responsive target genes as analyzed by RNA sequencing. The generic design of this system is likely transferable to other signaling pathways to analyze the kinetics of signal activation and propagation.
20.
Optogenetics-enabled discovery of integrated stress response modulators.
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Wong, F
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Li, A
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Omori, S
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Lach, RS
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Nunez, J
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Ren, Y
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Brown, SP
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Singhal, V
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Lyda, BR
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Batjargal, T
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Dickson, E
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Rodrigues Reyes, JR
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Uruena Vargas, JM
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Wahane, S
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Kim, H
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Collins, JJ
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Wilson, MZ
Abstract:
The integrated stress response (ISR) is a conserved stress response that maintains homeostasis in eukaryotic cells. Modulating the ISR holds therapeutic potential for diseases including viral infection, cancer, and neurodegeneration, but few known compounds can do so without toxicity. Here, we present an optogenetic platform for the discovery of compounds that selectively modulate the ISR. Optogenetic clustering of PKR induces ISR-mediated cell death, enabling the high-throughput screening of 370,830 compounds. We identify compounds that potentiate cell death without cytotoxicity across diverse cell types and stressors. Mechanistic studies reveal that these compounds upregulate activating transcription factor 4 (ATF4), sensitizing cells to stress and apoptosis, and identify GCN2 as a molecular target. Additionally, these compounds exhibit antiviral activity, and one compound reduced viral titers in a mouse model of herpesvirus infection. Structure-activity and toxicology studies highlight opportunities to optimize therapeutic efficacy. This work demonstrates an optogenetic approach to drug discovery and introduces ISR potentiators with therapeutic potential.
21.
Pharmacological interventions on GSK3β phosphorylation-mediated tau aggregation by modulating phase separation of tau proline-rich domain.
Abstract:
Tau pathological aggregation in neurofibrillary tangles is a hallmark of several neurodegenerative diseases, including Alzheimer's disease. Phase separation is a thermodynamic process that plays an important role in biomolecular membrane-less condensate formation, while abnormal phase separation of tau leads to pathological aggregate formation. However, the detailed molecular mechanism underlying tau condensation remains not fully understood. Moreover, whether condensation-based pharmacological intervention will be helpful for the treatment of tau-associated neurodegenerative diseases remains elusive. Here, we used an optogenetic tool (optoDroplets) in combination with cell biology and pharmacology to explore the contribution of different domains for tau condensation in cells, and we found that proline-rich domain (PRD) phosphorylation, which is mainly regulated by glycogen synthase kinase 3 β (GSK3β), plays important roles for tau condensation. Moreover, phosphorylation of tau PRD regulates its mis-localization on nuclear speckle. Interestingly and importantly, we found that pharmacological inhibition of GSK3β can impede abnormal tau condensation to slow down the tau-associated pathological process.
22.
Membranes arrest the coarsening of mitochondrial condensates.
Abstract:
Mitochondria contain double membranes that enclose their contents. Within their interior, the mitochondrial genome and its RNA products are condensed into ∼100 nm sized (ribo)nucleoprotein complexes. How these endogenous condensates maintain their roughly uniform size and spatial distributions within membranous mitochondria remains unclear. Here, we engineered an optogenetic tool (mt-optoIDR) that allowed for controlled formation of synthetic condensates upon light activation in live mitochondria. Using live cell super-resolution microscopy, we visualized the nucleation of small, yet elongated condensates (mt-opto-condensates), which recapitulated the morphologies of endogenous mitochondrial condensates. We decoupled the contribution of the double membranes from the environment within the matrix by overexpressing the dominant negative mutant of a membrane fusion protein (Drp1K38A). The resulting bulbous mitochondria had significantly more dynamic condensates that coarsened into a single, prominent droplet. These observations inform how mitochondrial membranes can limit the growth and dynamics of the condensates they enclose, without the need of additional regulatory mechanisms.
23.
Combining light-induced aggregation and biotin proximity labeling implicates endolysosomal proteins in early α-synuclein oligomerization.
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 previously unreported 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.
24.
Tau Oligomerization Drives Neurodegeneration via Nuclear Membrane Invagination and Lamin B Receptor Binding in Alzheimer’s disease.
Abstract:
The microtubule-associated protein tau aggregates into oligomeric complexes that highly correlate with Alzheimer’s disease (AD) progression. Increasing evidence suggests that nuclear membrane disruption occurs in AD and related tauopathies, but whether this is a cause or consequence of neurodegeneration remains unclear. Using the optogenetically inducible 4R1N Tau::mCherry::Cry2Olig (optoTau) system in iPSC-derived neurons, we demonstrate that tau oligomerization triggers nuclear rupture and nuclear membrane invagination. Pathological tau accumulates at sites of invagination, inducing structural abnormalities in the nuclear envelope and piercing into the nuclear space. These findings were confirmed in the humanized P301S tau (PS19) transgenic mouse model, where nuclear envelope disruption appeared as an early-onset event preceding neurodegeneration. Further validation in post-mortem AD brain tissues revealed nuclear lamina disruption correlating with pathological tau emergence in early-stage patients. Notably, electron microscopy shows that tau-induced nuclear invagination triggers global chromatin reorganization, potentially driving aberrant gene expression and protein translation associated with AD. These findings suggest that nuclear membrane disruption is an early and possibly causative event in tau-mediated neurodegeneration, establishing a mechanistic link between tau oligomerization and nuclear stress. Further investigation into nuclear destabilization could inform clinical strategies for mitigating AD pathogenesis.
25.
Optogenetic induction of TDP-43 aggregation impairs neuronal integrity and behavior in Caenorhabditis elegans.
Abstract:
Background
Cytoplasmic aggregation of TAR DNA binding protein 43 (TDP-43) in neurons is one of the hallmarks of TDP-43 proteinopathy. Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are closely associated with TDP-43 proteinopathy; however, it remains uncertain whether TDP-43 aggregation initiates the pathology or is a consequence of it.
Methods
To demonstrate the pathology of TDP-43 aggregation, we applied the optoDroplet technique in Caenorhabditis elegans (C. elegans), which allows spatiotemporal modulation of TDP-43 phase separation and assembly.
Results
We demonstrate that optogenetically induced TDP-43 aggregates exhibited insolubility similar to that observed in TDP-43 proteinopathy. These aggregates increased the severity of neurodegeneration, particularly in GABAergic motor neurons, and exacerbated sensorimotor dysfunction in C. elegans.
Conclusions
We present an optogenetic C. elegans model of TDP-43 proteinopathy that provides insight into the neuropathological mechanisms of TDP-43 aggregates. Our model serves as a promising tool for identifying therapeutic targets for TDP-43 proteinopathy.
