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Results for “animal behavior and cognition”

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

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bioRxiv2026

Dysregulated splenic glucocorticoid sensitivity in aging and an α-synuclein transgenic mouse model of Parkinson's disease

Introduction: Parkinson's disease (PD) and aging both disrupt hypothalamic-pituitary-adrenal (HPA) axis function and peripheral immune homeostasis. Whether aging or -synuclein (-syn) pathology alters glucocorticoid (GC) sensitivity of peripheral immune cells has not been investigated. Methods: Using an ex vivo GC sensitivity assay, we assessed the responsiveness of isolated and lipopolysaccharide (LPS)-stimulated splenocytes to the anti-inflammatory effects of increasing doses of corticosterone (CORT) in a wild-type (WT) aging cohort and in a PD -syn transgenic mouse model and respective age-matched controls. Results: Compared with splenocytes from 6-month-old WT mice, splenocytes from 20-month-old WT mice were less sensitive to 0.1 and 0.5 M CORT. Isolated splenocytes from PD vs. control mice were less sensitive to 0.05, 0.1, and 0.5 M CORT specifically at 16 months of age, but not at 6 or 20 months of age. As peripheral immune phenotyping revealed neither differences in HPA axis-related parameters nor in splenic GC receptor expression between PD and age-matched control mice at 6, 16, and 20 months, splenic GC resistance in PD mice at 16 months of age seems to be mediated by downstream GR signaling dysfunction. Conclusion: Together, our results support the hypothesis that -syn pathology accelerates an aging-associated decline in the peripheral sensitivity to anti-inflammatory GCs and may thereby sustain systemic and neuroinflammatory processes in PD.

neuroscience↗

bioRxiv2026

An agent-based 3D model of non-genetic adaptation in cancer tissues under electrical, mechanical, and hypoxic stress

Non-genetic adaptation enables cancer cells to alter their phenotype under stress without requiring new mutations. However, the mechanisms by which electrical, mechanical, and hypoxic cues combine to shape this process in 3D tissues remain poorly understood. This work presents an agent-based tumor model that integrates vascular oxygen supply, a globally imposed electric field, mechanically mediated crowding and compression cues, phenotype transitions, cell growth, mitosis, death, and inheritance of adaptive memory across division. The simulated tumors exhibit a three-stage trajectory consisting of necrosis onset, transient collapse of live mass, and partial regrowth accompanied by progressive accumulation of adapted cells. Continuous electrical stimulation produces a dose-dependent reduction in live mass while markedly increasing the adapted fraction, with comparatively limited changes in final necrotic burden. This response is strongly conditioned by mechanics and reshapes (and is reshaped by) adaptive capacity. Pulsed stimulation further shows that, in the model, electric field amplitude and temporal schedule jointly determine memory phenomena, phenotypic diversification, and growth recovery. These results show that coupling local oxygen availability, mechanical constraints, electrical forcing, and history-dependent phenotype transitions can generate distinct tissue-level patterns of phenotypic heterogeneity. Both stimulus magnitude and temporal protocol influenced the resulting population structure, suggesting that the history of physical stress may be an important determinant of adaptive dynamics in spatially organized tumor models.

biophysics↗

bioRxiv2026

Integrative single cell analysis of CD8+ T-cells across early and advanced oral cancers reveals signatures of anti-tumour activity

Tumour-targeting CD8 T cells drive responses to every major form of cancer immunotherapy. Identifying them, however, remains an unsolved problem in solid tumours. The antigens they recognize are rarely defined and almost never shared between patients. We profiled 51,459 CD8+ T cells by paired single-cell RNA and T-cell receptor sequencing across 28 samples from 17 HPV-negative oral cancers spanning primary tumours, draining lymph nodes, metastases, and pembrolizumab-treated recurrences. We found that clonotypes that were expanded and shared across anatomical sites and timepoints were enriched within tumours and progressively selected over disease evolution and checkpoint blockade. Designating these shared-expanded clones as putative tumour-targeting cells, we trained a machine learning classifier that identifies them from transcriptome data alone. This 108-feature random forest signature recapitulated programmes of tumour reactivity and generalized to an integrated atlas of 89,318 CD8+ T cells from independent cohorts, showing progressive enrichment from normal to malignant tissue, and localized to tumour-proximal niches in spatial transcriptomics. By demonstrating that clonal behaviour across space and time encodes tumour reactivity in the transcriptome, this work establishes a generalizable framework for mapping tumour-engaged immunity without knowledge of the underlying antigen.

cancer biology↗

bioRxiv2026

Persistent but variable effect of experimental laboratory burns on microbial community resistance, resilience, and function across contrasting boreal forest soils

Boreal forests stretch across vast swaths of the northern hemisphere, are shaped by wildfire, and play an important role in the global carbon cycle. Microorganisms play a critical role in soil nutrient cycling in these ecosystems, yet there are many open questions about the impacts of wildfire on microbially mediated soil biogeochemical cycles. In this study, we used laboratory burns and soil incubations of intact soil cores collected from two distinct soil types -- Histosols and Gleysols -- from boreal forest within Wood Buffalo National Park, Alberta, Canada, to assess burn effects on soil bacterial and fungal community composition and function. We compared resistance and resilience to burning for microbial communities vs. resistance and resilience to burning for soil pH and soil respiration to assess the relationships between burn-induced shifts in microbial community composition, the soil environment, and microbial activity. To link shifts in microbial community composition to potential community function, we measured glucose-specific carbon use efficiency (CUE) and assessed its relationship with weighted mean predicted 16S rRNA gene copy numbers for bacterial communities and FUNGuild-estimated relative abundance of putative symbiotrophic and saprotrophic fungi in burned and unburned soils. Microbial community resistance and resilience to burning varied across soil type with higher resistance of both bacterial and fungal communities from Histosols compared to the O horizons of Gleysols. This may be explained by a larger impact of burning on microbes in the thinner Gleysol O horizons. The relatively low resilience of bacterial and fungal communities to burning as well as the failure of resilience to increase with time since burning supports previous reports of post-burn microbial community recovery occurring over years rather than months. Burning caused a decrease in CUE with larger decreases following longer, hotter burns, which correlated with an increase in weighted mean predicted 16S rRNA gene copy number, raising the possibility that copy number could serve as a proxy for post-fire CUE in boreal forest soils, though more research is needed to constrain the effects of environmental conditions, substrates, and time since fire on this relationship. These findings suggest several ways in which burn-induced shifts in microbial community composition reflect altered microbial community function in meaningful ways for soil carbon cycling.

ecology↗

bioRxiv2026

IBD-Derived Colonic Fibroblasts Exhibit an Osteopontin-Enriched Secretome, and Osteopontin Restrains Human Colonic Organoid Maturation

Background: Intestinal fibroblasts are extensively remodeled in inflammatory bowel disease (IBD), yet the soluble stromal signals that directly influence epithelial maturation remain incompletely understood. We examined whether fibroblasts derived from inflamed IBD colon display an osteopontin (OPN; SPP1)-enriched secretory phenotype and whether extracellular OPN directly modifies non-neoplastic human colonic epithelium. Methods: Conditioned media from 5 noninflamed-associated fibroblast (NAF) and 4 inflammatory-associated fibroblast (IAF) cultures were analyzed in the validated multi-donor cytokine-array matrix, with orthogonal SPP1 RT-qPCR validation in a complementary fibroblast cohort. Recombinant OPN was then tested in human colonic organoids from 3 donors using donor-resolved molecular and functional analyses under standard, fibroblast-conditioned, and WNT-modified culture conditions. Donor identity defined biological replication. Results: OPN showed the strongest positive rank-based separation between IAF and NAF cultures: all 4 IAF values were higher than all 5 NAF values (Cliff's delta=1.00; exact Mann-Whitney P=0.0159; median ratio=3.64; Benjamini-Hochberg q=.19). Fibroblast RT-qPCR showed approximately 10-fold higher mean SPP1 expression in IAF than NAF cultures (P<.05). In organoids, OPN consistently reduced KRT20, FABP1, CA2, and MUC2 from Day 5 to Day 9. SOX9, HES1, and NOTCH1 increased at Day 9, whereas LGR5 and ALDH provided no evidence of canonical stem-cell expansion. Organoid-area and EdU responses were modest and donor dependent. Conclusions: IBD-derived colonic fibroblasts can display an OPN-enriched secretory phenotype. In human colonic organoids, OPN is sufficient to impair epithelial maturation, whereas its effects on growth and proliferation are variable and depend on the surrounding niche.

physiology↗

bioRxiv2026

Multivalent Adhesive Probe Atomic Force Microscopy (MAPA) for accessing dispersive adhesion of cells and biosurfaces.

Adhesion of cells is the key factor determining functioning of multicellular organisms. Viscoelastic properties of cells can be studied by multiple methods. However, attractiveness of cells or extracellular matrix without the elastic component (dispersive adhesion) is not accessible. We present an extension of force spectrometry technology: the Multivalent Adhesive Probe Atomic Force Microscopy (MAPA) that delivers dispersive adhesion maps of live cells and biosurfaces, and identifies differences unresolved by viscoelastic probing.

biophysics↗

bioRxiv2026

Loss of ELM1B impairs mitochondrial fission, matrix redox state and stress tolerance in Physcomitrium patens

Mitochondria are endosymbiont-derived organelles that play a central role in cellular metabolism, energy production and stress responses. While single mitochondria represent functional units, they continuously exchange their contents through fusion and fission, facing stress conditions as a dynamic population. To date, it remains largely unknown how stress alters mitochondrial dynamics in plants and how altered dynamics affect mitochondrial properties and plant stress resilience. Here, we investigate mitochondrial dynamics in response to oxidative stress in the non vascular model plant Physcomitrium patens. By creating mutants with impaired mitochondrial fission in different reporter lines for mitochondrial parameters, we additionally analyse effects of chronic changes to mitochondrial population dynamics. We found that Mito-Paraquat (MtPQ) treatment increased the glutathione redox potential EGSH in mitochondria, the cytosol and chloroplasts, as monitored via roGFP2-based genetically encoded biosensors. Mitochondria elongated within hours and showed a concomitant and heterogenous increase of matrix EOSred, that we propose as a marker for matrix protein damage. Mitochondrial fission mutants lacking PpELM1B (ELONGATED MITOCHONDRIA) displayed distinct changes of mitochondrial morphology parameters as determined by automated 3D-segmentation and feature mapping (MorphoMapper) of confocal z-stacks. Elongated mitochondria in Ppelm1bge lines showed an oxidative matrix EGSH shift and increased matrix EOSred while matrix mixing still occurred, albeit at the same slow rate as in wildtype, within days. Macroscopically, Ppelm1bge lines displayed reduced growth, decreased respiration, and a higher sensitivity to oxidative stress. Our results show that plant mitochondrial morphology and physiological parameters specifically shift in response to stress and impaired fission. Mitochondrial fission is vital to maintain a healthy mitochondrial population that sustains plant oxidative stress tolerance.

plant biology↗

bioRxiv2026

Immune-metabolic-redox ecosystems define spatially organized tumor states in head and neck squamous cell carcinoma.

Background: Spatial organization is increasingly recognized as a key determinant of tumor-immune interactions in head and neck squamous cell carcinoma (HNSCC). The GSE300147 Xenium spatial transcriptomic resource generated by McCord and colleagues established a framework for mapping spatially coordinated T-cell states in HNSCC. However, how tumor-enriched epithelial immune states relate to metabolic, redox, and stress-adaptive transcript programs remains incompletely defined. Methods: A secondary, data-driven reanalysis of GSE300147 was performed, focusing on 17 confirmed HNSCC Xenium sections after exclusion of a non-HNSCC ameloblastoma specimen. A total of 1,148,244 cells were analyzed, including 558,867 EpCAM+ tumor-enriched epithelial cells. Tumor-enriched epithelial cells were classified into Hot, Intermediate, and Cold states using a Composite Hotness framework integrating T-cell inflammatory signature score, checkpoint-associated signaling, CD274 expression, IFN/antigen-presentation signature score (IFN/AP), and tumor-immune proximity. Six metabolic ecosystem states, neighborhood profiling, spatial permutation testing, and an integrated Immune-Metabolic-Redox Ecosystem Score (IMRES) were then applied. Results: Immune activation was spatially heterogeneous across HNSCC sections. Immune-hot tumor-enriched epithelial regions showed not only inflammatory, checkpoint-associated, and antigen-presentation signature scores, but also coordinated metabolic, oxidative-redox, and stress-response transcript programs. IMRES, derived from available immune, metabolic, redox, and stress-response transcript components represented in the Xenium panel, increased progressively from Cold to Intermediate to Hot tumor-enriched epithelial states and was associated with NFE2L2, GDF15, HLA-DRA, CD274, KEAP1, and MDM2. Integrating IMRES with Composite Hotness identified a distinct Hot+IMREShigh ecosystem comprising 106,874 tumor-enriched epithelial cells. This state showed the strongest immune-active and stress-adaptive features and was positioned closer to immune populations than expected by random assignment. An alternative rank-based robustness analysis reproduced the IMRES-associated ecosystem axis and correlated with the original module-based score (Spearman r = 0.597). Conclusions: This secondary reanalysis extends the original spatial T-cell framework by defining a complementary tumor-centered immune-metabolic-redox ecosystem in HNSCC. IMRES provides a transcript-derived framework for identifying Hot+IMREShigh neighborhoods where immune activation, checkpoint signaling, metabolic remodeling, and stress adaptation converge, providing a hypothesis-generating framework for studying immune resistance and therapeutic vulnerability.

cancer biology↗

bioRxiv2026

Multimodal Protein Retrieval via Joint Representation Learning from Sequences and Cryo-EM Density Maps

Aligning protein sequences with cryo-EM density maps remains challenging due to limited paired data, structural heterogeneity, varying map resolutions, and the presence of multiple conformational states. In this work, we propose a multimodal representation learning framework that learns a shared latent space between protein sequences and cryo-EM density maps for cross-modal retrieval. Our approach combines pretrained protein sequence embeddings with a volumetric cryo-EM encoder trained using self-supervised representation learning and transfer learning. The resulting model enables bidirectional retrieval between sequences and density maps while learning biologically meaningful structural representations. Experimental results demonstrate strong retrieval performance across both sequence-to-map and map-to-sequence tasks, achieving median retrieval ranks of 2--3 within a database of 3,275 cryo-EM maps. The learned embedding space shows a clear separation between matched and unmatched sequence--map pairs and remains robust across varying cryo-EM resolutions. Additionally, the model generalizes across species, successfully retrieving conserved mouse protein structures using human sequence embeddings. Our findings demonstrate that joint latent-space learning provides a promising direction for connecting protein sequences with cryo-EM structural representations, with potential applications in structural retrieval, protein annotation, and multimodal biological representation learning.

bioengineering↗

bioRxiv2026

Patterned alginate hydrogel spatially guides collagen fibrillogenesis, viscoelasticity and endothelial cell invasion

Angiogenesis following injury has been shown to be driven by fibrillar proteins of the extracellular matrix (ECM), such as collagen. However, the use of protein-based biomaterials presents some challenges, such as uncontrolled degradation and limited tuneability. We demonstrate how to create patterned interpenetrating networks (IPNs) based on covalently crosslinked alginate and physically crosslinked collagen that provide suitable mechanical properties to support migration of endothelial cells (ECs) in a spatially controlled manner. Low molecular weight alginate is functionalized with norbornene (N) or tetrazine (T), which enables two independent covalent crosslinking methods: UV-mediated and degradable crosslinks with matrix metalloproteinase (MMP) sensitive peptides (Deg) and slower spontaneous N:T non-degradable crosslinks (noDeg). Using photolithography, patterns in degradation, collagen fibrillogenesis, microarchitecture and matrix viscoelasticity are created. The potential of such 3D patterned alginate-collagen (Alg-Col) IPNs to spatially guide EC invasion and proliferation was tested in a microfluidics platform resembling an early healing setting. Only regions combining collagen fibrillogenesis, alginate degradability and viscoelasticity demonstrated EC cell invasion similar to the ones found in vivo following injury. The 3D patterned Alg-Col IPNs are compatible with microfluidics, offer an strategy to widen the applications of protein-based hydrogels and present a versatile platform for tissue engineering and disease modeling.

bioengineering↗

bioRxiv2026

Estimating age and annual tooth growth rates in narwhals (Monodon monoceros) using computed tomography

The spiraling tooth of the narwhal (Monodon monoceros) has long intrigued scientists, but the growth rates of its "tusk" are poorly constrained due to the difficulty to age narwhal. To learn more about the population dynamics and life history of this exploited species, previous studies have used sectioned teeth to age narwhals and calibrate other ageing methods based on aspartic acid racemization, radiocarbon or trace element analysis. However, few such studies have been conducted due to the method's difficulty and the need to sacrifice the tooth. In this study, computed tomography (CT) was used on five teeth as a non-destructive means of estimating the age of narwhals, revealing different growth rates between erupted and embedded teeth during adolescence. Moreover, in combination with our reanalysis of all relevant literature, CT data clarify the annual growth rates of narwhal tusks, which peak before the age of 10 (~100 mm yr-1). This approach will be useful for investigating private and museum collections, and might also better constrain the use of trace element proxies in narwhal teeth and support sustainable harvest management.

zoology↗

bioRxiv2026

Seed Microbiome Transfer Mitigates Intergenerational Dysbiosis, Modulates Plant Defenses and Suppresses Foliar Disease

Antibiotic-induced disruption of plant-associated microbiomes has the potential to alter host health beyond the directly exposed generation, yet whether the effects of dysbiosis are transmitted through the seed microbiome remains unknown. Here, we investigated the intergenerational impacts of streptomycin-induced dysbiosis in tomato (Solanum lycopersicum), demonstrated that seed microbiome transfer (SMT) restores progeny microbiome function and disease resistance, and characterized the underlying physiological and genetic mechanisms. Parental streptomycin exposure altered the composition of progeny rhizosphere bacterial communities, reduced expression of defense-associated genes, and increased susceptibility to Xanthomonas perforans. Suppression of immune gene expression was strongly associated with increased disease severity, indicating that parental dysbiosis impaired progeny plants ability to mount effective immune responses. Transfer of the seed microbiome from healthy plant donors partially restored rhizosphere community composition, reduced disease severity and recovered defense gene expression of three genes. Together, our findings demonstrated that antibiotic exposure microbiome disturbance generates intergenerational legacy effects that influence plant immunity and disease susceptibility and seed microbiome transfer can counteract this dysbiosis across generations.

plant biology↗

bioRxiv2026

MIND the gap: methodological considerations and guidance for structural MRI similarity network analysis with MIND

Structural similarity networks quantify the similarity of structural properties across cortical regions, providing a macroscopic window onto the organisation of cortical architecture. Morphometric inverse divergence (MIND) is a multivariate metric of similarity between cortical areas, based on the Kullback-Leibler (KL) divergence between areal distributions of multiple MRI features or morphometric variables locally measured at voxel or vertex resolution. MIND has demonstrated technical robustness and biological validity and is increasingly widely used as a measure of cortico-cortical similarity in clinical and developmental network neuroscience. Here we provide in-depth methodological background on KL divergence and MIND, highlighting possible sources of bias, critical user decision points in the design of a MIND processing pipeline, and recommendations for technical risk mitigation in using MIND as a metric of cortical similarity. We use simulated data and observational MRI datasets from adults (UK Biobank, N = 500 T1-weighted and diffusion scans) and neonates (Developing Human Connectome Project, N = 752 T2-weighted scans), to show how the estimator of KL divergence implemented in MIND is potentially influenced or biased by five properties of input MRI feature maps: (i) their smoothness; (ii) the proportion of identical values; (iii) analysis in native or common space and the choice of vertex mesh resolution; (iv) parcellation choice; and (v) covariance between input features. We offer principled and practical guidance for investigators wanting to specify and implement the MIND processing pipeline that is best suited to the constraints and opportunities of the MRI data available to them. These recommendations outline which pipeline steps should be used sparingly, such as vertex map smoothing; which should be used with informed caution, such as parcellation choice or vertex mesh resampling; and which could be newly implemented for more robust estimation of MIND, such as the use of principal component analysis to preprocess multivariate MRI features. To support further development of structural MRI similarity network analysis, and wider adoption of robust MIND methods, we also publish the code used to generate the results in this paper as an open resource.

neuroscience↗

bioRxiv2026

Structure and epitope mapping of the conformational anti tau antibody DC11

Conformational antibody DC11 was previously shown to discriminate between physiological full length tau proteins and misfolded truncated tau proteins. It was also shown to catalyze in vitro tau aggregation, suggesting a connection with the pre-aggregation conformation of tau proteins. We have crystallized the Fab fragment of the DC11 antibody and characterized its binding with truncated tau proteins using ELISA, NMR and crosslinking mass spectrometry. The presumed model of the complex of DC11 antibody and truncated tau protein was obtained by docking tau321-391 conformations from coarse grained MD simulation into the antibody paratope.

biophysics↗

bioRxiv2026

Proteomic signatures of APOE ε4 across human tissues and cell types in Alzheimers disease

The apolipoprotein E {varepsilon}4 (APOE {varepsilon}4) allele is the strongest genetic risk factor for late-onset Alzheimers disease (AD). However, the underlying molecular mechanisms remain unclear. This study included 1691 participants from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP), 1226 participants from the Accelerating Medicines Partnership - Alzheimers Disease (AMP-AD) Diverse Cohorts Study, and 735 participants from the Alzheimers Disease Neuroimaging Initiative (ADNI). To characterise APOE {varepsilon}4 molecular effects, we analysed proteomic data from plasma, cerebrospinal fluid (CSF), and induced pluripotent stem cell (iPSC)-derived astrocytes and neurons, as well as transcriptomic and proteomic data from multiple brain regions. The association of APOE {varepsilon}4 with AD neuropathology was also examined. APOE {varepsilon}4 carriers shared a plasma proteomic signature enriched for immune processes, irrespective of AD diagnosis. A machine learning classifier trained on this signature discriminated APOE {varepsilon}4 carriers from non-carriers in an independent cohort using CSF proteomics. APOE {varepsilon}4 carriage was associated with higher Braak stages and Consortium to Establish a Registry for Alzheimers Disease (CERAD) score. However, only limited APOE {varepsilon}4-associated transcriptomic and proteomic changes were observed in bulk brain tissue, with poor cross-layer concordance. Proteomic analyses of iPSC-derived astrocytes and neurons further revealed cell-type-specific APOE {varepsilon}4-associated changes. APOE {varepsilon}4 is associated with a consistent proteomic signature across plasma and CSF. Its molecular effects in the brain differ across cell types, brain regions and molecular layers. These findings support the need for cell-type-resolved multi-omic studies to elucidate how APOE {varepsilon}4 confers AD risk.

neuroscience↗

bioRxiv2026

Burning down the mouse: Effects of wildfire and post-fire reseeding on Sin Nombre virus prevalence in its reservoir host

Worldwide, physical habitats and biological communities are being reshaped by wildfire. Such changes have obvious potential to alter pathogen ecology, yet few studies, outside of those focused on ectoparasites, have tested the effects of wildfire on pathogen prevalence in wildlife. Even fewer have focused on the impacts of strategies for post-fire remediation on pathogen circulation. Here, we investigated the effect of wildfire and wildfire mitigation on the prevalence and viral load of Sin Nombre virus (SNV) infection in its reservoir host, the western deer mouse, using a study design of matched burned, unburned, and post-burn reseeded sites in northern New Mexico. In total, we screened 411 individual deer mice for SNV via RT-qPCR and analyzed the effect of wildfire and wildfire mitigation on relative mouse abundance, individual infection probability, site-level prevalence and viral load. Relative abundance was highest at reseeded sites, and model selection indicated that habitat structure, particularly the gradient from closed canopy to open-herbaceous habitat, was consistently associated with increased relative abundance. Similarly, SNV prevalence was significantly higher in reseeded sites than either burned or unburned sites but did not differ in burned versus unburned sites. Viral load did not differ between burn history types, and zero-inflated gamma hurdle models did not identify any strong predictors of viral load. Serendipitously, we were also able to investigate the impacts of an El Nino Southern Oscillation (ENSO) cycle on patterns of infection in a subsample of sites that were studied during and one year after an ENSO year and found that SNV prevalence increased significantly post-ENSO. Both reseeding and ENSO deliver resource pulses that can support increases in mouse density and thereby enhance SNV transmission. The impacts of post-fire management practices on SNV prevalence in its reservoir host that were revealed in this study should be considered when implementing such strategies and when utilizing treated areas.

ecology↗

bioRxiv2026

Structural characterization the LlaI anti-phage defense system reveals insights into the evolution of nucleotide specificity and the organization of DNA binding in McrBC restriction complexes

Canonical McrBC enzymes are nucleotide-powered, motor-driven endonucleases that bind and cleave modified bacteriophage DNA. Non-canonical McrBC homologs like LlaI and BsuMI are distinguished by a unique three-gene organization and the ability to target DNA site-specifically. Here, we report the atomic-resolution crystal structures of the DNA-binding module LlaI.R1 and AAA+ motor LlaI.R2 from the Lactococcus lactis LlaI anti-phage defense system. The crystallized LlaI.R2 hexamer traps two distinct active site conformations that correlate to different states of the nucleotide hydrolysis cycle and reveal that the organization of the critical catalytic machinery present in canonical McrB homologs is also conserved in non-canonical R2 proteins. Although canonical McrB homologs are strictly GTP-specific, we find that the R2 proteins from LlaI and BsuMI do not discriminate between different nucleotides, even when in complex with their respective R1 partners. Using mutagenesis, we define surfaces on the LlaI.R1 structure that are critical for DNA-binding and interaction with LlaI.R2. These observations support computational modelling of the assembled LlaI restriction system bound to DNA. Together, our data provide new insights into the evolution of nucleotide specificity in McrBC restriction complexes and the molecular mechanisms governing McrBC-catalyzed DNA translocation and cleavage.

biochemistry↗

bioRxiv2026

FibrilNet maps conserved and tissue-specific molecular environments across systemic amyloidoses

Systemic amyloidoses are initiated by distinct amyloidogenic precursor proteins but frequently contain recurrent extracellular, complement, lipid-transport and matrix-remodelling components. Whether these recurrent proteins form a conserved systems-level environment across amyloid diseases, and how strongly that environment depends on precursor and tissue context, remains unresolved. We developed FibrilNet, a network framework that integrates experimentally defined amyloid proteomes with a human protein protein interaction graph and Gene Ontology derived semantic information. FibrilNet compares topology-only random walk with restart (RWR) with ontology aware semantic RWR in frozen leave-one-out module reconstruction and precursor-seeded prioritization tasks. The human graph contains 17,997 proteins and 925,977 physical interactions, with a 9-dimensional semantic representation of interaction context. In expanded cardiac transthyretin amyloidosis (ATTR), semantic-RWR increased mean reciprocal rank (MRR) from 0.00167 to 0.05015 and Recall@100 from 0.0199 to 0.3377, improving 132 of 151 held-out targets. Significant semantic gains were also observed in renal serum amyloid A amyloidosis (AA) and leukocyte chemotactic factor 2 amyloidosis (ALECT2). Across compact ATTR, light-chain amyloidosis (AL), AA and ALECT2 modules, APCS, VTN and TIMP3 formed a direct four-disease recurrent core, while APOE occurred in three of four modules. A tissue-aware ATTR analysis showed limited overlap between cardiac and neurologic modules (19 shared proteins; Jaccard 0.0569). In the hTTR-A97S peripheral-nerve model, semantic-RWR significantly improved reconstruction of the 202-protein mapped neurologic module, with the strongest evidence concentrated in the downregulated proteomic program. TTR-seeded propagation improved with semantic information but remained weak in absolute terms, separating precursor identity from the distributed downstream molecular environment. These results support a multilayer model in which a restricted conserved amyloid environment coexists with precursor-, tissue- and disease-specific organization

bioinformatics↗