Biology subjects

Sato, K.

Publications and source records attributed to Sato, K..

At least 19 recordsLinked to original sources

bioRxiv2026

Structure and antigenicity of the 2026 Bundibugyo virus glycoprotein

An outbreak of ebolavirus disease caused by a new zoonotic spillover of Bundibugyo virus (BDBV) is currently spreading at an unprecedented pace in the Democratic Republic of the Congo and Uganda. The outbreak has resulted in 7,733 cases with a case-fatality ratio of 48%, yet no BDBV-specific vaccines or therapeutics are available. The ebolavirus glycoprotein (GP) promotes viral entry and is the target of neutralizing antibodies and vaccine development. Here, we engineered a soluble, prefusion-stabilized GP trimer from a contemporary BDBV isolate and determined its cryo-electron microscopy structure bound to the broadly neutralizing antibody EBOV-515. It reveals the molecular basis for EBOV-515 cross-reactivity and suggests that the antibody inhibits viral entry by interfering with NPC1 engagement in addition to trapping GP in the prefusion conformation and hindering glycan cap cleavage. Mapping lineage-defining substitutions identified changes in GP1 and GP2, including R506S within an antigenic site targeted by multiple broadly neutralizing antibodies recognizing the fusion loop. Nevertheless, we found that several glycan cap-, GP base-, and HR2-directed antibodies cross-reacted and neutralized BDBV DRC/2026 GP pseudovirus with potency comparable or greater to that observed against earlier BDBV isolates and the Zaire ebolavirus Makona/2024 isolate. These findings define the antigenic properties of contemporary BDBV GP and delineate conserved epitopes as ideal targets for antibody therapeutics and for the development of pan-ebolavirus vaccines.

biochemistry↗

bioRxiv2026

A chromosome-level genome assembly of the classical model nematode Panagrellus redivivus for comparative studies of parasitism evolution

Panagrellus redivivus is a free-living nematode that served as an early model system for nematode biology prior to Caenorhabditis elegans. As a member of Clade IV, a clade harboring major plant-parasitic (e.g., Bursaphelenchus xylophilus) and animal-parasitic (e.g., Strongyloides spp.) species, P. redivivus represents a crucial, phylogenetically proximate non-parasitic reference for investigating the evolution of parasitism. Here, we present a chromosome-level genome assembly of P. redivivus constructed using Oxford Nanopore long reads, Illumina short reads, and Hi-C scaffolding. The assembly is resolved into five chromosome-scale scaffolds, with completeness validated by Hi-C contact maps and the identification of a non-canonical telomeric repeat motif. The assembly demonstrates high gene-space completeness (97.1% BUSCO) and contains 17,839 predicted protein-coding genes. Comparative orthology analysis revealed extensive orthogroup sharing between P. redivivus and Clade IV parasites, enabling comparative evolutionary studies with reduced confounding effects from deep lineage divergence. This high-quality genome provides a key resource for investigating the genetic basis of distinctive biological traits, including ovoviviparity, as well as gene family dynamics and parasite evolution.

genomics↗

bioRxiv2026

An integrated Rheo-NMR platform for real-time, site-specific kinetic analysis of amyloid formation

Amyloid fibrils are protein aggregates associated with neurodegenerative diseases. Their formation proceeds through protein- and condition-dependent microscopic pathways that can generate structurally and biologically distinct aggregates, yet these pathways are inferred from ensemble-averaged measurements. Amyloid formation is often slow under quiescent conditions, prompting agitation. However, conventional agitation precludes simultaneous high-resolution solution nuclear magnetic resonance (NMR) spectroscopy, limiting site-specific kinetic analysis of microscopic aggregation pathways. Here we present an integrated Rheo-NMR platform combining controlled shear flow, time-resolved NMR spectroscopy and mechanistic kinetic modeling to quantify site-specific amyloid-formation kinetics in a single, continuously monitored reaction. Applied to -synuclein under dilute and polyethylene glycol (PEG)-induced liquid-liquid phase separation (LLPS) conditions, the method revealed environment-dependent redistribution of kinetic signatures associated with primary nucleation-elongation and secondary nucleation-elongation pathways across the sequence. The platform distinguishes changes in overall aggregation rates from differences in residue-specific kinetic profiles, providing a quantitative framework for dissecting environment-dependent amyloid formation.

biochemistry↗

bioRxiv2026

Non-cell-autonomous removal of protein aggregates via trogocytosis

Protein aggregate formation can cause cell damage and contribute to tissue pathologies including neurodegeneration. Protein aggregates are normally eliminated by cell-intrinsic mechanisms of lysosomal (autophagic) degradation. However, degradative capacity varies between cell types, raising the possibility that high-capacity cell types, such as macrophages, may contribute to aggregate disposal from the low-capacity cells. Here, we show that cellular protein aggregates are removed by macrophages via trogocytosis -- a partial engulfment of the target cells. Lysosomal stress upon protein aggregate accumulation promotes cell surface expression of the transmembrane isoform of the macrophage growth factor CSF1 (tmCSF1), which is detected by macrophages through the CSF1 receptor to drive trogocytosis. Insufficient or impaired degradation of protein aggregates in lysosomes results in their transport along microtubules to the plasma membrane where they physically associate with tmCSF1. This enables macrophages to specifically trogocytose protein aggregates. These findings reveal a protein homeostasis system that eliminates protein aggregates in a non-cell-autonomous manner.

cell biology↗

bioRxiv2026

The "glue-gun ant" Lordomyrma azumai uses an adhesive thread secretion to immobilize opponents

In stinging Hymenoptera, the poison gland and its vesicle have been understood largely as sources of toxic, irritating, or antimicrobial compounds, which the sting injects into a target. However, external uses of poison gland secretions have also been reported: Pseudoneoponera (formerly Pachycondyla) froth a proteinaceous poison gland secretion into foam threads that entangle attacking ants, and Crematogaster smear opponents with a contact toxin generated on a spatulate sting from poison and Dufour gland products4. Here we report that workers of the myrmicine ant Lordomyrma azumai produce, in the poison vesicle, a secretion, likely proteinaceous, that solidifies upon extrusion into an adhesive thread. The sting is retained as the conduit, but the secretion it delivers is applied externally rather than injected, and acts as a structural material: workers wipe the thread onto opponents and tether them to the substrate. To our knowledge, no hymenopteran venom secretion functions as a solid thread; in the closest case, Pseudoneoponera3, the secretion entangles attackers as a foam rather than as a continuous solid filament.

animal behavior and cognition↗

bioRxiv2026

A reversible GNAS-PKA-RUNX2 checkpoint governs skeletal stem cell fate in fibrous dysplasia

Fibrous dysplasia (FD) arises from activating GNAS mutations that increase cAMP signaling in skeletal stem/progenitor cells (SSPCs), but the underlying mechanisms and whether the resulting fate imbalance can be reversed remain unclear. Using controlled GNAS induction with transcriptomic, pharmacologic, and cell-fate analyses, we identify a PKA-dependent checkpoint governing SSPC lineage commitment. GNASR201C redirects SSPCs toward osteoclastogenesis while suppressing osteoblast maturation; genetic or pharmacologic PKA inhibition reverses both effects, revealing this fate decision is dynamically reversible. Mechanistically, PKA phosphorylates RUNX2, the master regulator of osteogenesis, enforcing its cytoplasmic retention and blocking osteogenic transcription; a non-phosphorylatable RUNX2 mutant restores nuclear localization and osteoblast differentiation, defining RUNX2 phosphorylation as a disease-initiating molecular switch. Critically, PKA inhibition in vivo reduces fibrosis and osteoclast burden in established bone lesions, demonstrating reversibility even in advanced FD. These findings define a druggable GNAS-PKA-RUNX2 checkpoint and identify PKA inhibition as a strategy to reverse existing disease in FD.

cell biology↗

bioRxiv2026

Conditional Generation And Inpainting Of Non-coding RNA Sequences With Masked Discrete Diffusion

Designing functional non-coding RNA (ncRNA) is fundamental to synthetic biology and RNA therapeutics, yet generative modelling for ncRNA has received far less attention than protein design. We present RNA-MDLM, a framework that extends Masked Discrete Language Models (MDLM) to the conditional generation and inpainting of ncRNA. We make two additions: first, conditioning on RNA-type representations from a pretrained RNA language model, and second, a modified classifier-free guidance scheme (Mod-CFG) that interpolates among conditional, unconditional, and random-sequence probabilities for better control. We also introduce REPAINT GAMES, a benchmark of seven structured masking tasks to probe a model's performance on sequence patterns, structural motifs, and base-pairing per RNA type. Our model is trained on 4.6 million ncRNA sequences spanning six evaluable classes. It produces sequences whose composition and folding statistics closely match natural RNAs. Through extensive ablation studies, we find that the embedding-conditioned model achieves the best balance of structural fidelity, biological novelty, and inpainting accuracy, and its class label steers generation far more strongly than a plain label baseline. We further show that a model trained on a smaller, class-balanced subset can appear more realistic mainly by copying abundant natural sequences rather than learning their rules. We also benchmark against a masked-diffusion model and a family-specific VAE on ribozyme families, and find that a type-conditioned model like ours and a per-family model are solving different tasks, which must be accounted for in a fair comparison. We will release the code and the trained models.

biophysics↗

bioRxiv2026

Poxvirus gene repertoires are shaped by expansion-biased birth-and-death dynamics and genome architectural constraints

Poxviruses (family Poxviridae) are DNA viruses with exceptionally large genomes containing hundreds of genes. Yet the evolutionary processes contributing to their numerous gene repertoires remain insufficiently understood. Here, we inferred ortholog groups of genes across 58 poxvirus genomes and comprehensively analyzed gene gain, gene duplication, gene loss, horizontal gene transfer, and synteny conservation. Across poxviruses, coding capacity scaled linearly with genome length. Gene repertoires evolved through birth-and-death dynamics but generally expanded because gene gain cumulatively exceeded gene loss and gained genes subsequently underwent further duplication. Gene gain and duplication were concentrated in the terminal regions of most poxvirus genomes. In viral lineages whose gene repertoires expanded extensively, terminal-region expansion was accompanied by further accumulation of duplicated genes within the otherwise conserved central genomic regions. The phylogenetic placement of the bird-infecting genus Avipoxvirus, together with evidence that several horizontally acquired genes originated from mammals, raises the possibility of a mammalian origin for Avipoxvirus. Altogether, our findings reveal that poxvirus gene repertoire evolution is shaped by expansion-biased birth-and-death dynamics and genome architectural constraints.

evolutionary biology↗

bioRxiv2026

Conformational dynamics of an intrinsically disordered receptor enable signal transduction

Signal transduction is initiated when activated cell-surface receptors physically engage intracellular signaling proteins. Although structural and biochemical studies have established the molecular architecture of receptor tyrosine kinase (RTK) signaling, the earliest dynamic events that couple receptor activation to intracellular signal propagation have remained inaccessible because existing approaches provide static structural snapshots or ensemble-averaged measurements rather than direct observation of molecular motion. Here, using high-speed atomic force microscopy (HS-AFM), we directly visualize these initial molecular events at the single-molecule level in real time. Using fibroblast growth factor receptor 1 (FGFR1) as a model, we show that receptor autophosphorylation releases its intrinsically disordered juxtamembrane region, enabling extensive conformational dynamics of the kinase domain that permit productive engagement of the signaling adaptor FRS2, a key initiator of downstream RTK signaling. In contrast, a kinase-inactive mutation or the clinically approved FGFR inhibitor futibatinib restricts receptor motion, stabilizes a compact receptor configuration, and markedly reduces adaptor engagement. Molecular dynamics simulations suggest that the disruption of inhibitory interactions between the juxtamembrane region and the kinase domain provides a structural explanation for the observed receptor dynamics. Together, our findings uncover a previously inaccessible physical mechanism underlying the initiation of RTK signaling and establish HS-AFM as a powerful platform for visualizing receptor dynamics, providing a framework for mechanistic studies of signal transduction and for the development and mechanistic evaluation of compounds that modulate receptor signaling.

biophysics↗

bioRxiv2026

UTR-Diffusion: Conditional Diffusion Modeling for Multi-objective and Constrained UTR Design

Motivation: The 5-prime untranslated region (UTR) and the start-codon-proximal region of the coding sequence (CDS) jointly influence translation efficiency and local RNA secondary-structure stability, while synonymous codon choices throughout the CDS shape codon adaptation. Because the encoded protein is often predetermined, practical mRNA design must coordinate these quantitative objectives while preserving specified nucleotide sequences and amino-acid identities. Existing generative approaches typically address continuous-valued targeting, explicit sequence constraints, and codon-usage control separately rather than integrating all three within a single model. Results: We present UTR-Diffusion, a diffusion-based framework for 5-prime UTR and 5-prime UTR-CDS junction design. UTR-Diffusion conditions generation on continuous-valued MRL and MFE targets and supports nucleotide-level constraints, amino-acid-level constraints with synonymous-codon flexibility, and codon-adaptiveness control that modulates the sequence-level codon adaptation index (CAI). Systematic evaluations across dense MRL-MFE target grids showed that generated distributions shifted consistently with both targets, retained substantial diversity, and strictly preserved specified nucleotide sequences and amino-acid identities. Codon-adaptiveness control yielded distinct, monotonically ordered CAI levels that closely followed the specified adaptiveness targets. In comparative benchmarks, UTR-Diffusion outperformed representative existing methods in high-MRL optimization and precise MRL targeting for 5-prime UTR design, and achieved higher MRL, less-negative junction MFE, and higher CAI than peptide-preserving baselines in 50-nt 5-prime UTR-CDS junction design.

bioinformatics↗

bioRxiv2026

Mountain Centroid: RNA Ensemble Representation with Mountain Profiles

Background: RNA molecules form thermodynamic ensembles, but interpretation often requires a single representative structure. Existing base-pair centroid estimators assess agreement at the level of individual base pairs and do not directly target nesting depth along the sequence. Methods: We introduce Mountain Centroid, which minimizes expected squared mountain-profile distance, and derive dynamic programming algorithms with and without RNA pairing constraints. We also combine the Mountain Centroid objective with the base-pair centroid gain. Results: Across 21,254 RNAStrAlign sequences, Mountain Centroid had lower median normalized mean squared mountain distance (NMSMD) than minimum-free-energy (MFE) and base-pair centroid ({gamma} = 1) structures, whereas its median base-pair F1 was lower. Imposing RNA pairing constraints improved base-pair F1 for 59.35% of sequences and reduced it for 3.58%. At an illustrative weight, the combined objective had median base-pair F1 similar to MFE while retaining lower median NMSMD than MFE and all tested {gamma}-centroid settings. Conclusions: Mountain Centroid represents an RNA structural ensemble with a single secondary structure that reflects how nesting depth varies across nucleotide positions. Combining mountain-profile and individual-base-pair criteria allows their relative contributions to be varied.

bioinformatics↗

bioRxiv2026

A universal plug-and-display vaccine platform for mucosal and systemic immunity using Bacillus subtilis membrane vesicles

Many bacterial species naturally secrete membrane vesicles (MVs) that mediate the intercellular transport of biomolecules, including nucleic acids, proteins, and metabolites. Beyond their native physiological roles, MVs hold considerable potential for biomedical applications. Here, we demonstrate that MVs from several Bacillus species exhibit potent intrinsic adjuvant activity, efficaciously eliciting immune responses and facilitating antigen-specific antibody production in mice. Exploiting this adjuvanticity, we engineered a highly adaptable universal vaccine platform that uses B. subtilis MVs as self-adjuvanting carriers. This system employs a modular "plug-and-display" architecture that covalently anchors recombinant antigens to the MV surface through a multi-step bioconjugation cascade. After validation of this methodology using a model antigen, we adapted the platform to target Yersinia pestis, the causative agent of plague. We formulated a Y. pestis vaccine by labeling the MV surface with a modified capsule antigen fraction 1 (mCaf1). Intranasal administration of the mCaf1-MV vaccine effectively elicited both systemic and mucosal immunity. Crucially, this vaccine conferred highly efficacious protection against a lethal Y. pestis infection in a murine model. These findings demonstrate the exceptional protective efficacy of the B. subtilis MV platform and highlight its broad potential for the rapid development of mucosal vaccines against diverse emerging pathogens.

bioengineering↗

bioRxiv2026

Height-induced postural threat selectively facilitates spinal reflex in the tibialis anterior muscle during quiet standing

Long-latency stretch reflex and corticospinal excitability in the tibialis anterior muscle (TA) are facilitated when balance is threatened, even without background TA activity, suggesting supraspinal modulation as preparatory tuning for ankle stabilization. However, it remains unclear whether such tuning is evident at the spinal level and specific to the TA among lower-limb muscles. We therefore examined the effects of height-induced postural threat on multi-segmental monosynaptic spinal reflexes (MMR) in lower-limb muscles during quiet standing. Seventeen healthy young males performed 90-s standing tasks under three postural threat conditions, created by combining real and virtual reality (VR) heights: (1) Low-threat (real ground & VR ground), (2) Medium-threat (real table & VR ground), and (3) High-threat (real table & VR bridge). During each condition, transcutaneous spinal cord stimulation (tSCS) was applied to the lumbar spine to elicit MMR in lower-limb muscles. Electromyograms (EMG) were recorded from six muscles of the right leg: vastus medialis (VM), biceps femoris (BF), TA, soleus (SOL), medial (MG), and lateral gastrocnemius (LG). MMR excitability was quantified as peak-to-peak EMG amplitude. Fear ratings and electrodermal activity were higher in High-threat than Low-threat (all p < 0.05), confirming successful threat induction. Peak-to-peak EMG amplitude in the TA was significantly higher in High-threat than Low-threat (17.1% increase, p = 0.0393), whereas background TA activity remained absent across conditions. These results indicate that TA has unique function to facilitate spinal excitability as a preparatory tuning for ankle stabilization. Key pointsO_LIPrevious studies have shown the supraspinal facilitation of the tibialis anterior muscle without background muscle activation as a preparatory tuning for ankle stabilization. C_LIO_LITo test the hypothesis that such tuning is also evident at the spinal level and specific to the tibialis anterior muscle, this study examined whether height-induced postural threat modulates multi-segmental monosynaptic reflex excitability in lower-limb muscles using transcutaneous spinal cord stimulation. C_LIO_LIElectrodermal activity and fear ratings increased under height-induced postural threat, confirming the successful induction of postural threat. C_LIO_LIUnder height-induced postural threat, the multi-segmental monosynaptic reflex was selectively facilitated in the tibialis anterior muscle, while its background activity remained absent. C_LIO_LIOur findings demonstrate selective facilitation of spinal excitability in the tibialis anterior muscle, which may serve as preparatory tuning for ankle stabilization under threat to balance. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/742625v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@19fde78org.highwire.dtl.DTLVardef@c6aa8dorg.highwire.dtl.DTLVardef@e73a76org.highwire.dtl.DTLVardef@af393d_HPS_FORMAT_FIGEXP M_FIG C_FIG Abstract figure legendWhen balance is threatened, corticospinal excitability and long-latency stretch reflex in the tibialis anterior muscle (TA) are facilitated even in the absence of background TA activity, suggesting supraspinal preparatory tuning for ankle stabilization. This study tested the hypothesis that such facilitation is also expressed at the spinal level and is specific to the TA. Participants completed 90-s quiet standing trials under three different height-induced postural threat conditions. During each trial, transcutaneous spinal cord stimulation was delivered over the lumbar spine to elicit multi-segmental monosynaptic reflexes (MMR) in multiple lower-limb muscles. High-threat condition increased fear ratings and electrodermal activity, indicating successful threat induction. Moreover, MMR excitability was selectively increased in the TA under High-threat condition despite the absence of background TA activity. These findings suggest that spinal facilitation is selectively expressed in the TA and may reflect preparatory tuning for ankle stabilization under threat to balance.

neuroscience↗

bioRxiv2026

Improved Protein Semi-Synthesis Enables Biophysical Studies of Thioamide Destabilization of β-Sheet Interactions

Thioamides are natural post-translational modifications of the peptide backbone and can be introduced synthetically to probe protein folding or functionalize peptides for translational applications. In this work, we demonstrate that thioamide-containing peptides with C-terminal thioesters can be efficiently generated using Knorr pyrazole activation and used in subsequent native chemical ligation reactions to generate thioamide containing proteins. We compare this method to acyl azide activation and find that both routes provide similar yields. We also investigate ultrasound-mediated desulfurization of the ligation site cysteine for potential advantages over chemical radical initiators. Scaling up our syntheses allows us to study thioamide perturbations to the {beta}-sheet region of the B1 domain of protein G (GB1) as well as {beta}-strand interactions in amyloid fibrils of the Parkinsons disease protein -synuclein. In both contexts, we observe dramatic destabilization of the {beta}-sheet networks, manifested in decreased GB1 thermal stability and altered folding and slowed aggregation of -synuclein. These findings illustrate the impact that a single atom substitution can have on cooperative hydrogen bonding networks and prompt future study of both systems.

biochemistry↗

bioRxiv2026

BRCA2 and RAD54B FxPP motifs Bind DMC1 Filaments through Persistent and Transient Interfaces

During meiosis, double-strand DNA breaks are programmed to initiate homologous recombination. The DMC1 recombinogenic filament is central to the repair of these breaks. However, the three-dimensional structures of the protein-protein interfaces regulating the assembly and activity of this filament have not been described yet. We and others previously reported that in BRCA2, a P-motif called PhePP binds to DMC1 in its oligomeric and filament states. Here we identified a similar P-motif in the DNA translocase RAD54B. We solved the cryo-electron microscopy (cryo-EM) structures of BRCA2 and RAD54B P-motif peptides bound to a ssDNA-DMC1 filament at 1.9-2.0 [A] resolution. While these peptides only share the sequence F-[IV]-P-P, they bind to the filament through larger 9-10 residue core sequences with superimposable structures. Both peptides bind to a hydrophobic and negatively charged site, named the P-site, on a single DMC1 protomer and stabilize the ssDNA-DMC1 filament. Mutagenesis experiments and molecular dynamics simulations identified additional transient interactions between positively charged residues of the peptides and negatively charged patches distributed on the DMC1 protomers. We propose that BRCA2 and RAD54B stably dock at the P-site of a single DMC1 protomer but also bridge two DMC1 protomers within the presynaptic filament via transient contacts with the adjacent protomer.

biochemistry↗

bioRxiv2026

PKProbDesign: RNA inverse folding including pseudoknots by optimizing thermodynamic folding probability

Motivation: RNA inverse folding, the design of RNA sequences that fold into specified target secondary structures, is a central problem in RNA design, with applications in functional RNA engineering, synthetic biology, and nucleic-acid therapeutics. This task becomes especially challenging for pseudoknotted target structures because pseudoknots break the nested structure assumed by standard thermodynamic folding models. Existing pseudoknot inverse-folding methods often rely on structure-predictor-based objectives. These methods do not directly optimize the probability that a sequence folds into the specified pseudoknotted target structure. Such optimization requires an evaluator that can assign a folding probability to the specified target within a pseudoknot-aware ensemble. Results: We present PKProbDesign, a sampling-based inverse-folding framework that directly optimizes a thermodynamic folding-probability objective for pseudoknotted targets. For each target, sampled sequences are scored by combining the folding probability of a pseudoknot-free scaffold with the conditional folding probability of the remaining extension component. On 254 unique density-2 PseudoBase++ targets, PKProbDesign achieved the highest pseudo-joint folding probability on 245 targets, compared with 6 for DesiRNA, 3 for MODENA, and none for antaRNA. Conclusions: PKProbDesign demonstrates that pseudoknot inverse folding can be formulated with target folding probability as its objective rather than structure-prediction agreement alone. By combining scaffold decomposition with conditional folding-probability evaluation based on CParty, the method provides a practical folding-probability-based approach to designing sequences for density-2 pseudoknotted targets. Availability: The source code of PKProbDesign is available at https://github.com/TakumiOtagaki/PKProbDesign.

bioinformatics↗

bioRxiv2026

A bistable UV-sensitive opsin from a reef building coral showing a switchable and tunable regulation of Gs-signaling by different wavelengths of light

Cnidarians possess large number of opsins in their genomes for their various photoreceptive functions. In particular, they uniquely possess Gs-coupled opsins that induce intracellular cAMP accumulation in a light-dependent manner. These Gs-coupled opsins, cnidopsins, are powerful optogenetic tools manipulating cAMP-dependent cellular responses. In this study, we characterized a cnidopsin, named as AtCnidop3a, from the coral Acropora tenuis as a Gs-coupled and UV-sensitive bistable pigment. This cnidopsin showed a large spectral shift upon activation from absorption maxima from 395 nm to 560 nm, and the resting and activated states are interconvertible by illumination with UV (or violet) and orange light. The activated state efficiently activated Gs proteins and elevated intracellular cAMP levels in mammalian cultured cells. To engineer the opsin mutant that can be turned on and off upon long wavelength light illumination by utilizing the large spectral separation, negatively charged amino acids were introduced near the retinal Schiff base region. Among tested opsin mutants, the Y1133.28E mutant is capable of being activated by green light unlike the wild-type while retaining the property of being inactivated by orange light like the wild-type, indicating successful conversion of the opsin to a visible light sensitive bistable pigment. The visible light-induced cAMP regulation of the Y1133.28E mutant was enhanced by an additional L942.61G substitution. Our characterization and engineering of the cnidopsin revealed functional diversity of cnidarian opsins and its potential utility as optogenetic tools regulating Gs-dependent physiological responses.

biochemistry↗

bioRxiv2026

MECP2-mutant marmosets exhibit primate-specific phenotypes of Rett syndrome

We used genome editing to generate MECP2-knockout marmosets and establish a new primate model for Rett syndrome (RTT), a neurodevelopmental disorder. MRI analysis of this marmoset model revealed diminished cortico-cortical connections, particularly those originating in the prefrontal cortex. Detailed histological analysis revealed reduced dendritic arborization and synaptic density, particularly in the upper layers of the cerebral cortex. Cortical layer II/III excitatory neurons appeared to be immature based on single-nucleus RNA sequencing and spatial transcriptomics, while PVALB-positive interneurons exhibited upregulation of neuronal maturation-related transcripts. Moreover, the neurodevelopmental disease gene GABAB receptor 2 (GABBR2) emerged as a conserved downstream target of MECP2, illuminating a cellular cascade that could be targeted in preclinical and therapeutic drug development. Many of the gene expression changes observed in the marmoset model are common in RTT patients, thereby highlighting molecular links from cell type-specific phenotypes in the marmoset model to the RTT clinical presentation.

neuroscience↗