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Science Journals

Peer-reviewade publikationer — 287 artiklar

Computational mechanisms for temporal integration in the anterior claustrum
The claustrum, with its extensive reciprocal connections to nearly all cortical regions, has long been hypothesized as a key hub for integrating diverse cognitive, sensory and motor information. However, despite its anatomical connectivity, whether and how it functionally integrates different inputs to generate coherent representations has remained unclear. Here, we developed a recurrent neural network (RNN) trained via supervised learning on behavioral metrics of delayed escape—a behavioral paradigm that requires integration of temporally separated task-relevant signals. A subset of RNN neurons exhibited dynamics similar to those of anterior claustral neurons during this behavior. These neurons formed a recurrent cluster, a structure supported by in vitro stimulation experiments in claustral brain slices. We analyzed the computational properties of this claustrum-like cluster via dimensionality reduction of population activity. The network showed nonlinear integration of temporally distributed inputs and increased synergistic information. Rather than settling into attractors, integrated information was dynamically encoded along continuously evolving neural trajectories. Notably, similar trajectory patterns associated with dynamic integration were observed in claustral recordings, suggesting the model’s biological plausibility. We propose that the anterior claustrum dynamically integrates task-relevant input signals over time and broadcasts the evolving representation to downstream brain regions capable of reading and interpreting it in a context-dependent manner.
LFA-1 interaction with GBP-130 on <i>Plasmodium falciparum</i>-infected red blood cells mediates NK cell activation and parasite control
Natural killer (NK) cells contribute to early immunity against <i>Plasmodium falciparum</i> by recognizing and eliminating infected red blood cells (iRBCs), a process mediated in part by the integrin LFA-1. However, the cognate parasite ligand for LFA-1 has remained unknown. Here, we identify glycophorin binding protein-130 (<i>Pf</i>GBP-130) as a surface-expressed ligand on iRBCs that binds the I-domain of LFA-1 (LFA-1 αI). Using an LFA-1 αI-Fc fusion protein, we demonstrate stage-specific binding to iRBCs, and LC-MS/MS analysis of immunoprecipitates of αI-Fc bound to iRBC revealed <i>Pf</i>GBP-130 as a high-confidence interactor. Recombinant <i>Pf</i>GBP-130 binds NK and THP-1 cells in an LFA-1-dependent manner. Co-culture assays show that <i>Pf</i>GBP-130 promotes NK cell activation and degranulation and facilitates contact-dependent killing of iRBCs. Neutralizing antibodies against <i>Pf</i>GBP-130 significantly impair these responses. Our findings establish <i>Pf</i>GBP-130 as the LFA-1 ligand on iRBCs, providing new insight into NK cell-mediated immunity in malaria and identifying a potential target for host-directed interventions.
High-frequency spike inference with particle Gibbs sampling
Calcium-sensitive fluorescent indicators enable monitoring of spiking activity in large neuronal populations in animal models. Despite the plethora of algorithms developed over the past decades, accurate spike-time inference methods for spike rates exceeding 20 Hz are lacking. More importantly, little attention has been devoted to the quantification of statistical uncertainties in spike time estimation, which is essential for assigning confidence levels to inferred spike patterns. To address these challenges, we introduce (1) a statistical model that accounts for bursting neuronal activity and baseline fluorescence modulation and (2) apply a Monte Carlo strategy (particle Gibbs with ancestor sampling) to estimate the joint posterior distribution of spike times and model parameters. Our method is competitive with state-of-the-art supervised and unsupervised algorithms, as evaluated on the CASCADE benchmark datasets. Analysis of fluorescence transients recorded with the ultrafast genetically encoded calcium indicator GCaMP8f demonstrates that our method can resolve interspike intervals as short as 5 ms. Overall, our study describes a Bayesian inference method for detecting neuronal spiking patterns and quantifying their uncertainty. The use of particle Gibbs samplers enables unbiased estimates of spike times and all model parameters, providing a flexible statistical framework for testing more specific models of calcium indicators.
Hsp70 is phosphorylated in a conserved response to DNA damage and contributes to cell cycle control
Hsp70s are essential molecular chaperones that are increasingly recognized to be regulated by post-translational modifications. Here, we show that phosphorylation of a conserved threonine (T495), previously shown to be exploited by a <i>Legionella pneumophila</i> kinase to inhibit Hsp70, occurs endogenously in human cells in response to DNA damage, particularly when base excision repair is overburdened. This modification is cell cycle dependent, and in yeast, phosphomimetic or phosphonull Hsp70 variants disrupt G1/S progression under normal and DNA-damaging conditions. Biochemically, the phosphomimetic T495E mutation locks Hsp70 in an open-like conformation without blocking substrate engagement. Together, our results reveal a conserved mechanism by which dynamic Hsp70 phosphorylation regulates the G1/S transition and delays cell cycle progression during DNA damage, highlighting how pathogen-derived insights can uncover fundamental cell biology principles.
Inhibitory columnar feedback neurons are involved in motion processing in <i>Drosophila</i>
Visual motion information is essential to guiding the movements of many animals. The establishment of direction-selective signals, a hallmark of motion detection, is considered a core neural computation and has been characterized extensively in primates, mice, and fruit flies. In flies, the circuits that produce direction-selective signals rely on feedforward visual pathways that connect peripheral visual inputs to the dendrites of the ON and OFF-direction-selective cells. Here, we describe a novel role for feedback inhibition in motion computation. Two GABAergic neurons, C2 and C3, connect to neurons upstream of the direction-selective T4 and T5 cells, and blocking C2 and C3 affects direction selectivity in T4/T5. In the ON pathway, this is likely achieved by C2-mediated suppression of responses in the major T4 input neuron Mi1. Together, C2 and C3 suppress responses to non-preferred stimuli in both T4 and T5. At the behavioral level, feedback inhibition temporally sharpens responses to ON-moving stimuli, enhancing the fly’s ability to discriminate visual stimuli that occur in quick succession. GABAergic inhibitory feedback neurons thus constitute an essential component within the circuitry that computes visual motion.
Hyperactivated glycolysis drives spatially patterned Kupffer cell depletion in MASLD
Metabolic dysfunction-associated steatotic liver disease (MASLD) progression is characterized by hepatic inflammation and cell death, yet the mechanisms underlying Kupffer cell (KC) loss remain poorly understood. Here, we sought to elucidate the metabolic basis of KC death during MASLD. Using metabolomics, immunostaining, and flow cytometry, we evaluated metabolic alterations and KC death throughout early MASLD progression. We found that KC death is an early hallmark of MASLD, exhibiting greater susceptibility and a spatial distribution consistent with KC zonation. Moreoever, KCs undergo progressive metabolic reprogramming toward enhanced glucose utilization during MASLD development, which is correlated with KC death. In combination with biochemical agonist, isotope tracing, and primary KC culture, we further demonstrated that augmented glycolytic metabolism directly drives KC death in vitro. Consistently, using <i>Chi3l1</i>-deficient mice, we further demonstrated that increased glucose utilization accelerates KC death in vivo. Together, these findings establish a causal link between glycolytic activation and KC loss during MASLD progression, highlighting glucose metabolic pathways as potential therapeutic targets to preserve KC homeostasis and mitigate MASLD.
Cognitive simplicity drives collective route improvements in homing pigeons
Cognitive abilities are central to how animals navigate complex environments. Beyond individual cognition, group living can also enhance navigation by pooling individually acquired information. One way this may be achieved is by following experienced leaders, which requires recognizing expertise within group members. Alternatively, accurate decisions could also emerge without expert opinions, through simpler mechanisms like the ‘wisdom of crowds’ principle that average out individual biases. Consequently, collective navigation strategies range from cognitively complex to simple, and yet, the prevalence or interplay of different collective strategies in nature remains unexplored. In this study, we asked: what is the navigation mechanism, requiring minimal cognitive demands, that is necessary and sufficient to quantitatively replicate the experimental results of a 2017 study on homing pigeons (<i>Columba livia</i>), which showed that sequential chains of bird pairs flying home—similar to a game of telephone—led to shorter homing routes compared to control birds flying individually or in fixed pairs. Our results show that the experimental data aligns closely with the simplest strategy—route averaging. Surprisingly, the complex mechanism of selectively propagating the best flight through social learning offered no additional advantage. We further observed that mixed strategies, although not supported by the experimental data, in theory combined advantages from both averaging and active selection of better routes, resulting in even greater performance. Hence, our results highlight the potential for future research to investigate selective pressures shaping the evolution of cultural learning and trade-offs among different decision mechanisms theoretically available to social animals in nature.
Molecular architecture of the tumor microenvironment caused by <i>BRCA1</i> and <i>BRCA2</i> somatic mutations in human lung adenocarcinoma
Homologous recombination repair (HRR) deficiency is associated with improved immunotherapy responses in non-small cell lung cancer (NSCLC) patients. The HRR genes <i>BRCA1</i>/<i>2</i> are key regulators of DNA repair, yet their impact on the tumor microenvironment (TME) in lung adenocarcinoma (LUAD) remains unclear. Using single-cell sequencing and multi-omics data, we characterized <i>BRCA1/2</i> mutation-associated transcriptional programs, immune cell composition, and functional alterations in T cells, investigating the molecular and immune architecture of BRCA-mutant LUAD patients. <i>BRCA1</i>/<i>2</i> mutations were associated with increased genomic instability and poor prognosis in LUAD patients, but predicted better clinical outcomes following immune checkpoint blockade (ICB) treatment. <i>BRCA1</i> mutations correlated with an upregulated type I IFN/IFN-γ signature and CD8<sup>+</sup> T cell activation. <i>BRCA2</i> mutations were associated with alveolar/stress/inflammatory responses and enhanced MHC-II antigen presentation, linked to CD4<sup>+</sup> T cell differentiation. Both alterations coincided with reduced CD28 co-stimulation and CTL activity, hinting at immune evasion. We identified two tissue-resident memory T cell (Trm) subsets as predictors of clinical outcomes and ICB response. <i>BRCA1</i> mutations were associated with CD8<sup>+</sup> Trm expansion, whereas <i>BRCA2</i> mutations were linked to tumor CD4<sup>+</sup> Trm expansion and peripheral T/NK cell cytotoxicity. Furthermore, a cancer-promoting program activated by <i>BRCA1</i> mutation was vulnerable to histone deacetylase inhibitors, which inhibited LUAD tumor growth. This study provides a preliminary characterization of the BRCA-mutant TME in LUAD patients, revealing distinct transcriptional and immune patterns that highlight differences in <i>BRCA1/2</i>-associated molecular architecture and offer a framework for improving therapy efficacy in LUAD.
Multi-talker speech comprehension at different temporal scales in listeners with normal and impaired hearing
Comprehending speech requires deciphering a range of linguistic representations, from phonemes to narratives. Prior research suggests that in single-talker scenarios, the neural encoding of linguistic units follows a hierarchy of increasing temporal receptive windows. Shorter temporal units like phonemes and syllables are encoded by lower-level sensory brain regions, whereas longer units such as sentences and paragraphs are processed by higher-level perceptual and cognitive areas. However, the brain’s representation of these linguistic units under challenging listening conditions, such as a cocktail party situation, remains unclear. In this study, we recorded electroencephalogram (EEG) responses from both normal-hearing and hearing-impaired participants as they listened to individual and dual speakers narrating different parts of a story. The inclusion of hearing-impaired listeners allowed us to examine how hierarchically organized linguistic units in competing speech streams affect comprehension abilities. We leveraged a hierarchical language model to extract linguistic information at multiple levels—phoneme, syllable, word, phrase, and sentence—and aligned these model activations with the EEG data. Our findings showed distinct neural responses to dual-speaker speech between the two groups. Specifically, compared to normal-hearing listeners, hearing-impaired listeners exhibited poorer model fits at the acoustic, phoneme, and syllable levels, as well as the sentence levels, but not at the word and phrase levels. These results suggest that hearing-impaired listeners experience disruptions at both shorter and longer temporal scales, while their processing at medium temporal scales remains unaffected.
A quantitative pipeline for whole-mount deep imaging and analysis of multi-layered organoids across scales
Whole-mount 3D imaging at the cellular scale is a powerful tool for exploring complex processes during morphogenesis. In organoids, it allows examining tissue architecture, cell types, and morphology simultaneously in 3D models. However, cell packing in multilayered organoid tissues hinders both deep imaging and quantification of cell-scale processes. To address these challenges, we developed an experimental and computational pipeline to extract properties at scales ranging from cell to tissue. The experimental module is based on two-photon imaging of immunostained organoids. The computational module corrects for optical artifacts, performs accurate 3D nuclei segmentation and reliably quantifies gene expression. We provide the computational module as a user-friendly Python package called Tapenade, along with napari plugins which enable joint data processing and exploration across scales. We demonstrate the pipeline by quantifying 3D spatial patterns of gene expression and nuclear morphology in gastruloids, revealing how local cell deformations and gene co-expression relate to tissue-scale organization. This quantitative pipeline improves our understanding of gastruloid development, and lays the groundwork for a wide range of multi-layered organoids and tumoroids systems
In situ mutational screening and CRISPR interference define <i>apterous</i> cis-regulatory inputs during compartment boundary formation
The establishment of tissue axes is fundamental during embryonic development. In the <i>Drosophila</i> wing, the anterior/posterior (AP) and the dorsal/ventral (DV) compartment boundaries provide the basic coordinates around which the tissue develops. These boundaries arise as a result of two lineage decisions, the acquisition of posterior fate by the selector gene <i>engrailed</i> (<i>en</i>) and dorsal fate by the selector gene <i>apterous</i> (<i>ap</i>). While the <i>en</i> expression domain is set up during embryogenesis, <i>ap</i> expression begins only during early wing development. Thus, the correct establishment of the <i>ap</i> expression pattern relative to <i>en</i> must be tightly controlled. Here, we functionally investigate the transcriptional inputs integrated by the early <i>ap</i> enhancer (apE) and their requirement for correct boundary formation. Detailed mutational analyses using CRISPR/Cas revealed a role for apE in positioning the DV boundary relative to the AP boundary, with apE mutants often displaying mirror-image anterior wing duplications. We then designed and applied methods to accomplish tissue-specific enhancer disruption via dCas9 expression. This approach allowed us to dissect the spatiotemporal requirement for apE function, clarifying the mechanism by which apE misregulation leads to AP defects. Base-pair-resolution analyses of apE uncovered a single HOX-binding site essential for wing development that, when mutated, led to wingless flies. We demonstrated that the transcription factors Pointed (Pnt), Homothorax (Hth), and Grain (Grn) are required for apE function, and the HOX gene Antennapedia (Antp) contributes to early wing development. Together, our results provide a comprehensive molecular basis of early <i>ap</i> activation and the developmental consequences of its misregulation, shedding light on how compartmental boundaries are set up during development.
Sexual dimorphism in sensorimotor transformation of optic flow
Motion vision underpins a wide range of adaptive behaviours essential for individual and species survival. In hoverflies, some visual behaviours are sexually dimorphic, including for example male high-speed pursuit of conspecifics matched by improved optics and faster photoreceptors. Other visual behaviours are sexually monomorphic, with for example similar foraging flight speeds in male and female hoverflies. However, whether the descending neurons responsible for sensorimotor transformation of optic flow are sexually dimorphic is unknown. To address this, we combined morphological analysis with electrophysiology of optic flow sensitive descending neurons and compared neural responses to the behavioural output in tethered hoverflies. We found that while optomotor flight behaviour is largely sexually monomorphic, the underlying neural responses are sexually dimorphic, especially at higher optic flow velocities. Additionally, behavioural responses were noticeably slower than neural responses. Together, our findings uncover a nuanced, sex- and stimulus-dependent sensorimotor transformation, shaped by both neural architecture and behavioural demands.
Involuntary feedback responses reflect a representation of partner actions
We have a remarkable ability to seamlessly and rapidly coordinate actions with others, from double Dutch to dancing. Humans use high-level partner representations to jointly control voluntary actions, while other work shows lower-level involuntary feedback responses to sudden visual perturbations. Yet, it is unknown if a high-level partner representation can be rapidly expressed through lower-level involuntary sensorimotor circuitry. Here, we test the idea that a partner representation influences involuntary visuomotor feedback responses during a cooperative sensorimotor task. Using two experiments and dynamic game theory predictions, we show that involuntary visuomotor feedback responses reflect a partner representation and consideration of a partner’s movement cost (i.e., accuracy and energy). Collectively, our results suggest there is top-down modulation from high-level partner representations to lower-level sensorimotor circuits, enabling fast and flexible feedback responses during jointly coordinated actions.
Isolation of small extracellular vesicles from small volumes of blood plasma using size exclusion chromatography and density gradient ultracentrifugation
Small extracellular vesicles (sEVs) are heterogeneous biological vesicles released by cells under both physiological and pathological conditions. Due to their potential as valuable diagnostic and prognostic biomarkers in human blood, there is a pressing need to develop effective methods for isolating high-purity sEVs from the complex milieu of blood plasma, which contains abundant plasma proteins and lipoproteins. Size exclusion chromatography (SEC) and density gradient ultracentrifugation (DGUC) are two commonly employed isolation techniques that have shown promise in addressing this challenge. In this study, we aimed to determine the optimal combination and sequence of SEC and DGUC for isolating sEVs from small plasma volumes, in order to enhance both the efficiency and purity of the resulting isolates. To achieve this, we compared sEV isolation using two combinations: SEC-DGUC and DGUC-SEC, from unit volumes of 500 μL plasma. Both protocols successfully isolated high-purity sEVs; however, the SEC-DGUC combination yielded higher sEV protein and RNA content. We further characterized the isolated sEVs obtained from the SEC-DGUC protocol using flow cytometry and mass spectrometry to assess their quality and purity. In conclusion, the optimized SEC-DGUC protocol is efficient, highly reproducible, and well suited for isolating high-purity sEVs from small blood volumes.
Developmental constraints mediate the reversal of temperature effects on the autumn phenology of European beech after the summer solstice
Accurate projections of temperate tree growing seasons under climate change require representing developmental constraints that determine tree resource allocation. A phenological ‘switch point’ after the summer solstice (21 June) has been proposed, with pre-solstice warming advancing autumn phenology and post-solstice warming delaying it. We propose that this switch is flexible and occurs at the compensatory point between early-season development and late-season temperature effects. We performed trans-solstice climate manipulation experiments on potted European beech (<i>Fagus sylvatica</i>) saplings to test (i) how spring leaf-out timing and June-August temperatures influence end-of-season timing (bud set and leaf senescence) and (ii) whether daytime and nighttime temperatures before and after the solstice have distinct effects. Bud set and senescence were tightly coupled (<i>R<sup>2</sup></i>=0.49), with stronger bud responses. Each day of delayed leaf-out postponed bud set by 0.24±0.06 days and senescence by 0.22±0.08 days. July full-day cooling delayed autumn phenology in late-leafing individuals (bud set +4.9±2.6 days; senescence +3.1± 2.8 days) but had a negligible impact on early-leafing trees. August full-day cooling advanced both stages. Pre-solstice daytime cooling had no effect, while post-soltice daytime cooling advanced autumn phenology. Nighttime cooling consistently delayed bud set. These findings support the Solstice-as-Phenology-Switch model and highlight the central role of developmental progression in constraining growing seasons. Faster early-season development – especially under nighttime warming – moves trees past the switch earlier, increasing sensitivity to late-season cooling and thereby triggering earlier autumn phenology. Phenology models should incorporate these developmentally-mediated and diel-specific temperature responses.
Insights into perceptual learning
A form of short-term memory called serial dependence can predict how effectively perceptual learning transfers to novel visual locations.
Lipopolysaccharide stimulates dynamic changes in B cell metabolism to promote proliferation
Naive B cells exit quiescence and enter a proliferative state upon activation, ultimately differentiating into antibody-secreting or memory B cells. Toll-like receptor (TLR) ligands, such as lipopolysaccharide (LPS), can serve as physiological stimuli to initiate this transition. Using quantitative proteomics, we show that TLR4 engagement induces metabolic reprogramming in murine B cells, increasing the expression of amino acid transporters and cholesterol biosynthetic enzymes. The amino acid transporter SLC7A5 is markedly upregulated following LPS stimulation, and conditional deletion of <i>Slc7a5</i> impairs B cell proliferation, underscoring its essential role in B cell activation. LPS also elevates intracellular cholesterol levels, and inhibition of the rate-limiting enzyme HMG-CoA reductase blocks proliferation. This effect was mediated by a dual requirement for cholesterol metabolism and protein prenylation downstream of HMG-CoA reductase. Notably, this was not unique to TLR4 signalling but is also observed in B cells activated via TLR7, TLR9, CD40, or the B cell receptor. Together, these findings reveal that metabolic rewiring, including amino acid uptake and cholesterol metabolism, is an essential feature of B cell activation and proliferation.
The nucleus accumbens shell regulates hedonic feeding via a rostral hotspot
The medial nucleus accumbens shell (medNAcSh) is a key regulator of hedonic feeding, controlling reward consumption through its projections to downstream structures. Recent studies showed that the primary cellular mediators of these effects are dopamine 1 receptor-positive striatal projection neurons (D1-SPNs). Specifically, D1-SPN activity gets inhibited during reward consumption, and such inhibition is necessary and sufficient to authorize consumption, independent of metabolic need. Anatomically, the medNAcSh spans 1–1.5 mm along the rostro-caudal axis in mice, and previous studies have reported functional gradients along this axis. For instance, pharmacological studies have suggested that rostral rather than caudal medNAcSh regulates appetitive behavior. However, the mechanisms underlying this topographical gradient remain unknown. Here, we hypothesized that D1-SPNs contribute to this gradient by regulating hedonic feeding via a specific hotspot in the rostral medNAcSh. Using calcium monitoring with fiber photometry in mice, we show that rostral medNAcSh D1-SPNs demonstrate inhibitory responses during reward consumption, while caudal D1-SPNs do not. Consistently, optogenetic stimulation of rostral D1-SPNs inhibits consumption, while stimulation of caudal D1-SPNs had minimal effects, confirming the existence of a functional rostro-caudal gradient. Importantly, we observed no differences between rostral and caudal D1-SPNs in their responses to aversive stimuli, suggesting that the D1-SPN gradient is specific to appetitive contexts. To investigate potential molecular correlates of this functional gradient, we leveraged open-source anatomy datasets and performed fluorescent in situ hybridization, identifying <i>Stard5</i> and <i>Peg10</i> as markers enriched in the rostral and caudal medNAcSh, respectively. Finally, we developed a novel Stard5-Flp driver line to selectively target the rostral hotspot and demonstrated that Stard5+ neurons recapitulate rostral D1-SP…
Single-cell transcriptomics-informed induced pluripotent stem cells differentiation to tenogenic lineage
During vertebrate embryogenesis, axial tendons develop from the paraxial mesoderm and differentiate through specific developmental stages to reach the syndetome stage. While the main roles of signaling pathways in the earlier stages of differentiation have been well established, pathway nuances in syndetome specification from the sclerotome stage have yet to be explored. Here, stepwise differentiation of human induced pluripotent stem cells to the syndetome stage is shown, using chemically defined media and small molecules that were modified based on single-cell RNA-sequencing and pathway analysis. A significant population of branching off-target cells differentiating toward a neural phenotype overexpressing Wnt was identified. Further transcriptomics post-addition of a WNT inhibitor at the somite stage and onwards revealed not only total removal of the neural off-target cells, but also increased syndetome induction efficiency. Fine-tuning tendon differentiation in vitro is essential to address the current challenges in developing a successful cell-based tendon therapy.
The multifaceted role of EXOC6A in ciliogenesis
Ciliogenesis is a highly ordered process that requires membrane trafficking, fusion, and maturation. In this study, we investigated EXOC6A, a component of the exocyst complex known for secretory vesicle trafficking and fusion, and found that it interacts with myosin-Va (Myo-Va) during ciliogenesis. EXOC6A colocalizes with Myo-Va at various stages of ciliogenesis, including preciliary vesicles, ciliary vesicles (CVs), and ciliary sheath membrane during ciliogenesis. We found that EXOC6A vesicles are actively recruited, integrated, and exit from the CVs and the ciliary sheath, implying that EXOC6A vesicles may facilitate continuous cilia membrane remodeling during ciliogenesis. Importantly, EXOC6A knockout impairs ciliogenesis, arresting most cells at the CV stage and preventing recruitment of NPHP and MKS module components to the transition zone. Furthermore, EXOC6A vesicles are transported to the mother centriole via a dynein-, microtubule-, and actin-dependent mechanism. Our results suggest that EXOC6A functions in both early and late stages of ciliogenesis, and is involved in orchestrating vesicle dynamics, cilia membrane remodeling, and formation.
Twelve phosphomimetic mutations induce the assembly of recombinant full-length human tau into paired helical filaments
The assembly of tau into amyloid filaments is associated with more than 20 neurodegenerative diseases, collectively termed tauopathies. Electron cryo-microscopy (cryo-EM) structures of brain-derived tau filaments revealed that specific structures define different diseases, triggering a quest for the development of experimental model systems that replicate the structures of disease. Here, we describe 12 phosphomimetic serine/threonine-to-aspartate mutations in tau, which we term PAD12, that collectively induce the in vitro assembly of full-length three-repeat tau into filaments with the same structure as paired helical filaments extracted from the brains of individuals with Alzheimer’s disease. Solution-state nuclear magnetic resonance spectroscopy suggests that phosphomimetic mutations in the carboxy-terminal domain of tau may facilitate filament formation by disrupting an intramolecular interaction between two IVYK motifs. PAD12 tau can be used for both nucleation-dependent and multiple rounds of seeded assembly in vitro, as well as for the seeding of tau biosensor cells. PAD12 tau can be assembled into paired helical filaments under various shaking conditions, with the resulting filaments being stable for extended periods of time. They can be labelled with fluorophores and biotin. Tau filaments extracted from the brains of individuals with Alzheimer’s disease have been known to be made of hyperphosphorylated and abnormally phosphorylated full-length tau, but it was not known if the presence of this post-translational modification is more than a mere correlation. Our findings suggest that hyperphosphorylation of tau may be sufficient for the formation of the Alzheimer tau fold. PAD12 tau will be a useful tool for the study of molecular mechanisms of neurodegeneration.
Uncovering the electrical synapse proteome in retinal neurons via in vivo proximity labeling
Electrical synapses containing Connexin 36 (Cx36) represent the main means for direct electrical communication among neurons in the mammalian nervous system. However, little is known about the protein complexes that constitute these synapses. In the present study, we applied different BioID strategies to screen the interactomes of Connexin 36 and its zebrafish orthologue Cx35.1 in retinal neurons. For in vivo proximity labeling in mice, we took advantage of the Cx36-EGFP strain and expressed a GFP-nanobody-TurboID fusion construct selectively in AII amacrine cells. For in vivo BioID in zebrafish, we generated a transgenic line expressing a Cx35.1-TurboID fusion under control of the <i>Cx35.1</i> promoter. Both strategies allowed us to capture a plethora of molecules that were associated with electrical synapses and showed a high degree of evolutionary conservation in the proteomes of both species. Besides known interactors of Cx36 such as ZO-1 and ZO-2, we have identified more than 50 new proteins, such as scaffold proteins, adhesion molecules, and regulators of the cytoskeleton. Moreover, we determined the subcellular localization of these proteins in mouse retina and tested potential binding interactions with Cx36. Among these new interactors, we identified signal-induced proliferation associated 1 like 3 (Sipa1l3), a protein that has been implicated in cell junction formation and cell polarity, as a new scaffold of electrical synapses. Interestingly, Sipa1l3 was able to interact with ZO-1, ZO-2, and Cx36, suggesting a pivotal role in electrical synapse function. In summary, our study provides the first detailed view of the electrical synapse proteome in retinal neurons, which is likely to apply to electrical synapses elsewhere.
Multimodal MRI marker of cognition explains the association between cognition and mental health in the UK Biobank
Cognitive dysfunction often co-occurs with psychopathology. Advances in neuroimaging and machine learning have led to neural indicators that predict individual differences in cognition with reasonable performance. We examined whether these indicators explain the relationship between cognition and mental health in the UK Biobank (<i>n</i>&gt;14,000). Using machine learning, we quantified the covariation between cognition and 133 mental health indices and derived neural indicators of cognition from 72 neuroimaging phenotypes across diffusion-weighted MRI (dwMRI), resting-state functional MRI (rsMRI), and structural MRI (sMRI). With commonality analyses, we investigated how much of the cognition–mental health covariation is captured by each indicator and neural indicators combined within and across MRI modalities. The predictive association between mental health and cognition was at <i>r</i>=0.3. Neuroimaging captured 2.1 to 25.8% of the cognition-mental health covariation. Combining phenotypes within modalities improved the explanation to 25.5% for dwMRI, 29.8% for rsMRI, and 31.6% for sMRI, and combining them across modalities enhanced the explanation to 48%. We present an integrated approach to derive multimodal MRI markers of cognition that can be transdiagnostically linked to psychopathology, demonstrating that the predictive ability of neural indicators extends beyond the prediction of cognition itself, enabling us to capture cognition-mental health covariation.
MORC2 mediates transcriptional regulation through liquid-liquid phase separation
MORC2 is a chromatin-associated ATPase essential for transcriptional silencing and genome stability, yet the biophysical principles governing its regulatory activity remain elusive. Here, we demonstrate that full-length MORC2 undergoes biomolecular condensation to form dynamic nuclear assemblies, a process fundamentally required for its repressor function. Endogenous MORC2 forms discrete, dynamic condensates in neurons from <i>Morc2a<sup>EGFP</sup></i> chimeric mice, supporting the physiological relevance of these assemblies in vivo. Mechanistically, a 3.1 Å crystal structure of coiled-coil 3 (CC3) identifies a dimeric scaffold that serves as a structural hub, while multivalent ‘sticker’ interactions between an intrinsically disordered region (IDR) and a newly defined IDR-binding domain (IBD) drive condensation. We show that DNA acts as a molecular scaffold that triggers MORC2 condensation, which in turn allosterically stimulates its ATPase activity. Critically, by employing a ‘killswitch’ strategy to decouple assembly from internal fluidity, we reveal that only dynamic MORC2 condensates, not static aggregates or condensation-deficient mutants, can restore transcriptional regulation in <i>MORC2</i>-knockout cells. Furthermore, pathogenic variants linked to CMT2Z and SMA differentially perturb these material properties and enzymatic turnover, providing a mechanistic link between condensate dysregulation and human neuropathies. Together, our findings establish a DNA-templated condensation mechanism for MORC2 and provide a molecular framework for understanding how the material state of chromatin-associated machinery dictates gene regulation and disease pathogenesis.