Biology subjects

Zhang, T.

Publications and source records attributed to Zhang, T..

At least 73 records · Page 4Linked to original sources

bioRxiv2026

Integrated optimization of experimental and computational workflows improves genome recovery in long-read gut metagenomics

Short-read metagenomic sequencing has been widely applied in microbial research due to its high quality and decreasing cost. However, short reads are inherently fragmented, which limits assembly contiguity and the recovery of complete microbial genomes. In contrast, long-read sequencing, with significantly longer read lengths, helps overcome these limitations. Achieving complete and accurate genome recovery is the core goal of metagenomics. To address this challenge, we systematically evaluated and optimized the long-read metagenomic workflow, from sample processing to computational assembly, using the CycloneSEQ platform.

bioinformatics↗

bioRxiv2026

Telomere Dysfunction in Human Astrocytes Drives Acrocentric Chromosome Instability and Nucleolar Reorganization

Loss of p53 and Rb enables continued cell division despite progressive telomere erosion, ultimately triggering telomere crisis. While recent work has clarified mechanisms of chromatin bridge resolution, the longitudinal dynamics of structural damage through crisis remain incompletely understood. We transduced normal human astrocyte (NHA) cells with HPV18 E6/E7 and tracked them across extended population doublings. NHA E6/E7 cells showed progressive telomere shortening, anaphase bridges, and a growth plateau consistent with crisis. Multicolor FISH revealed subclonal chromosomal abnormalities largely invisible to short-read sequencing, with acrocentric chromosomes disproportionately affected: chromosome 13 was abnormal in over 92% of metaphases, and chromosomes 21 and 22 were similarly enriched. Translocations involving chromosome 13 were transient, replaced at later passages, while numerical aberrations persisted. Immunofluorescence revealed compact spherical nucleoli replaced by dispersed necklace-like structures, indicating a large-scale reorganization of nucleolar structure in response to telomere dysfunction. To determine whether these changes reflected altered chromosomal organization in the nucleus, we performed Hi-C and deployed KaryoScope, our alignment-free k-mer-based approach that recovers trans-chromosomal signal from repetitive acrocentric short arms. Inter-chromosomal contacts among nucleolar organizing region-bearing acrocentric chromosomes were markedly and persistently depleted in E6/E7 cells. Together, cytogenetic, imaging, and chromatin-contact data identify the nucleolus as a structural nexus linking telomere dysfunction to large-scale genomic rearrangement.

cancer biology↗

bioRxiv2026

Rhythmic temporal structure organizes recurrent dynamics to support sequential working memory

Rhythmic temporal structure improves working memory, but how this benefit emerges from recurrent dynamics remains unclear. Here, we trained excitatory-inhibitory recurrent neural networks with short-term synaptic plasticity to perform a sequential delayed match-to-sample task with either regular or jittered sample timing. Rhythmic input produced a small but reliable improvement in task accuracy and was associated with more differentiated population trajectories during encoding. This behavioral advantage was accompanied by an organization of population dynamics around the dominant input frequency: temporal regularity progressively brought stimulus arrivals closer to preferred encoding phases, modulated phase advancement during stimulus presentation, and reduced the deviation of inter-stimulus phase-progression frequency from the dominant input rhythm. As a result, internal oscillations increasingly tracked the temporal structure of the input across the sequence, providing a phase-based scaffold for encoding ordered information. This scaffold preferentially supported temporal-order representations rather than uniformly enhancing all stimulus features. Decoding analyses further showed that stronger temporal regularity increased the fidelity and persistence of stimulus information in both neuronal activity and synaptic efficacy, whereas perturbing synaptic efficacy produced the largest impairment during delay-period maintenance. These findings suggest that rhythmic input supports sequential working memory by imposing a reliable temporal structure on recurrent dynamics and stabilizing synaptic-state representations.

neuroscience↗

bioRxiv2026

Immunometabolic Remodeling of Perivascular Adipose Tissue in Murine Lupus: Implications for Lupus Vasculopathy

BackgroundPatients with systemic lupus erythematosus (SLE) face markedly increased cardiovascular disease (CVD) risk driven by mechanisms beyond traditional risk factors. Thoracic aortic perivascular adipose tissue (tPVAT) is dysfunctional in lupus and exacerbates endothelial dysfunction, yet the molecular basis of this dysfunction remains poorly defined. MethodsIntegrated multi-omics profiling, including bulk RNA-seq, untargeted proteomics, lipidomics, and high-dimensional spectral flow cytometry, was performed on tPVAT from 15-week-old MRL/lpr mice (active lupus, n = 4-6) and MRL control mice (n = 5-6). Adipogenic differentiation capacity of tPVAT adipose stromal and progenitor cells (ASPCs) from MRL/lpr was assessed by Oil Red O staining at 5 (pre-dieasea) and 15 weeks (active disease), with subcutaneous ASPCs used as depot controls. ResultsTranscriptomic profiling of tPVAT from MRL/lpr mice identified 2,742 upregulated and 1,494 downregulated genes (adjusted p < 0.001, |log2FC| > 1), with strong activation of interferon, IL6-JAK-STAT3, and TNFA signaling pathways together with suppression of fatty acid metabolism, oxidative phosphorylation, and adipogenic pathways. Proteomic and lipidomic analyses were concordant, revealing broad downregulation of mitochondrial bioenergetic machinery, depletion of cardiolipin and acylcarnitines, and enrichment of ceramide phosphoinositols and lysophosphatidylcholines. Cardiolipin strongly correlated with the mitochondrial/metabolic protein module (r = 0.95) and inversely with the immune/inflammatory protein module (r = -0.92). Spectral flow cytometry confirmed marked CD45+ leukocyte infiltration dominated by T cells, together with a significantly reduced Treg/CD4+ ratio indicating loss of local immunoregulatory balance. ASPCs derived from PVAT of 15-week-old MRL/lpr mice exhibited impaired white and beige adipogenic differentiation, while APCs from PVAT of 5-week-old MRL/lpr mice, and from subcutaneous adipose tissues of 15-week-old MRL/lpr mice, had normal white and beige differentiation, consistent with an acquired, depot-specific, disease-stage-dependent progenitor defect in PVAT of MRL/lpr mice. ConclusionsLupus tPVAT undergoes a concordant cross-platform molecular reprogramming of mitochondrial bioenergetic genes coupled with establishment of an interferon-dominant immune niche and acquired loss of ASPC adipogenic capacity. These findings provide a molecular framework for lupus PVAT dysfunction and identify restoration of mitochondrial function, suppression of interferon-driven inflammation, and renewal of progenitor differentiation as potential therapeutic strategies for lupus vasculopathy.

molecular biology↗

bioRxiv2026

Tryptophan degradation by intestinal Bacteroides induces anti-tumor immunity and limits melanoma growth

Defining mechanisms used by gut microbiota to control anti-tumor immunity may offer novel therapeutic modalities. Here, we demonstrate that Bacteroides rodentium and closely related Bacteroides uniformis species induce anti-tumor immunity and limit melanoma development when colonized in either germ-free (GF) mice, mice with a complex microbiome, or WT mice. Enhanced CD8+ T cell infiltration seen in tumors of mice harboring B. rodentium coincided with increased expression of immune-stimulating pathways and activation of bone marrow-derived dendritic cells that were co-cultured with the B. rodentium secretome. Metabolomic analyses of cecal samples from GF mice colonized with Altered Shedlar Flora (ASF) plus B. rodentium revealed lower tryptophan levels than in ASF-colonized controls, and WT mice fed a tryptophan-deficient diet exhibited inhibition of melanoma development. In silico genomic reconstruction of metabolic pathways revealed that both B. rodentium and B. uniformis harbor tryptophanase A (TnaA) and aromatic amino transferase (ArAT) genes, both of which function in tryptophan degradation. Administration of a B. uniformis harboring TnaA mutant failed to inhibit melanoma growth in gnotobiotic mice. Notably, administration of indoles, but not kynurenines, also effectively inhibited melanoma development, increasing immune cell infiltration into the tumors. Correspondingly, levels of bacterially encoded tryptophan-degrading enzymes were higher in cohorts of melanoma patients responding to immune checkpoint blockade. These findings highlight a novel mechanism of anti-tumor immunity and tumor growth inhibition dependent on the tryptophan degradation products, indoles, produced by intestinal Bacteroides species.

cancer biology↗

bioRxiv2026

The Par complex regulates apical-basal cell polarity through modulation of FAK signaling homeostasis

Cell polarity complexes are essential for embryogenesis, but their regulatory mechanisms during early developmental transitions remain incompletely understood. Here, we individually deleted the Crumbs, Par, and Scrib polarity complexes in mouse embryonic stem cells (mESCs). While loss of any single complex did not affect pluripotency or proliferation, deletion of Par complex disrupted the naive-to-primed transition and impaired subsequent differentiation, particularly lumen formation in neural tube organoids. Mechanistically, Par complex deficiency led to hyperphosphorylation of focal adhesion kinase (FAK) at the primed stage, driving a morphological shift from flat monolayer clusters to dome-shaped colonies. FAK inhibition rescued the aberrant morphology. Upstream, Par complex loss increased AKT phosphorylation, which remodeled extracellular matrix (ECM) and regulated integrin signaling via FURIN-LEFTY, ultimately modulating FAK activity. In addition, conditioned medium from wild-type cells partially rescued differentiation defects in Par knockout cells in a LEFTY-dependent manner. These phenotypes were consistently observed in naive-to-primed transition, neural stem cell differentiation, embryoid body formation, teratoma assays, and neural tube organoid differentiation. Together, these findings establish a Par complex-AKT-FURIN-LEFTY-ECM-integrin-FAK signaling cascade that links apical-basal polarity to early lineage specification and morphogenesis, providing a mechanistic framework for how polarity cues are translated into developmental outcomes. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/722465v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@179e0adorg.highwire.dtl.DTLVardef@8d83bdorg.highwire.dtl.DTLVardef@c425fforg.highwire.dtl.DTLVardef@19a8ee5_HPS_FORMAT_FIGEXP M_FIG C_FIG Significance StatementThis study elucidates the molecular mechanism by which the Par complex regulates the establishment of cell polarity. The authors demonstrate that the Par complex promotes the expression of the protein convertase FURIN via AKT signaling, thereby enhancing the maturation and secretion of LEFTY protein. This process remodels the ECM and modulates integrin signaling, ultimately regulating FAK activity and controlling the establishment of cell polarity. These findings reveal how polarity cues govern early lineage specification and morphogenesis, with implications across multiple developmental contexts.

developmental biology↗

bioRxiv2026

A dataset of simultaneous two-photon calcium imaging and auditory discrimination behavior

The emerging field of artificial intelligence for neuroscience relies heavily on high-quality, standardized datasets. Data linking high-dimensional neural population dynamics with complex behavior is crucial for advancing the field of brain-computer interfaces. However, few existing datasets provide these paired modalities in a standardized, AI-ready format, limiting their immediate utility for computational modeling. Here, we present a large-scale dataset comprising simultaneous two-photon calcium imaging of the primary auditory cortex (A1) and detailed behavioral records in mice. The animals performed an auditory two-alternative forced-choice (2AFC) categorization task, classifying tones as low or high frequency by licking left or right water ports. The raw neural and behavioral data were preprocessed, synchronized, and formatted into trial-aligned multi-dimensional tensors. Comprehensive validation confirms that the recorded populations exhibit consistent, high-fidelity temporal dynamics and distinct frequency tuning across all experimental conditions. To evaluate the datasets capacity for neural decoding, we benchmarked it across diverse machine learning architectures and deep learning networks. By bridging biological recordings and behavior, this open-access dataset serves as a valuable benchmark for developing novel decoding algorithms and testing brain-inspired computational models.

neuroscience↗

bioRxiv2026

CMAS dampens anti-tumor immunity and associates with response to neoadjuvant immunotherapy in melanoma

Identifying immune-regulatory pathways to predict response is crucial for the efficacy of immune checkpoint blockade (ICB) immunotherapies. Sialylation is upregulated in tumor cells and modulates immune responses in cancer, yet its impact on patient clinical outcome and the spatial organization of the tumor microenvironment remain unclear. Here, using publicly available single-cell RNA sequencing data we show that expression of the sialylation master regulator CMAS in melanoma cells correlates with poorer patient survival. Using a murine melanoma model, we demonstrate that Cmas deletion in tumor cells severely impaired tumor growth and improved anti-tumor lymphoid and myeloid cell responses, increasing tumor cell-intrinsic susceptibility to interferon-gamma-, CD4+ T cell-, and macrophage-mediated killing. Single-cell spatial transcriptomics on neoadjuvant ICB-treated melanoma patient tumor biopsies revealed that CMAS expression in tumor cells inversely correlated with tumor cell proximity to and activation status of T cells and macrophages. Furthermore, expression of CMAS in tumor cells was increased in patients who did not respond to immunotherapy, compared to responders. Overall, our work identifies CMAS as a key modulator of tumor-immune dynamics associated with survival and response to neoadjuvant ICB immunotherapy in melanoma patients.

cancer biology↗

bioRxiv2026

Metabolic dehalogenation of halomethanes by mercury methylators

Mercury (Hg) methylators play key roles in the global Hg cycle. Nonetheless, the Hg methylators are widely present in Hg-absent environments and the Hg methylation is a cometabolic process without cell growth, which leave the origin and evolution of the Hg methylation as a mystery. Here, we reported the CCl4/trihalomethane-to-dihalomethane dehalogenation by model Hg methylators in a metabolic way. Heterologously-expressed HgcAB catalyzed both the CCl4 dechlorination and Hg methylation. Halomethanes were shown to sustain the Hg-methylation community without adding external carbon source, electron donor and acceptor. Metadata analyses suggested the halomethane dehalogenation potential of Hg methylators at the global scale. These results, together with much higher global flux and kinetic Vmax of the metabolic halomethanes dehalogenation relative to the co-metabolic Hg methylation, suggested halomethanes as the potential HgcAB substrates for the evolution of Hg methylation.

microbiology↗

bioRxiv2026

Aligned recordings of neural spiking activity and licking behavior in thirsty mice

Electrophysiological data, which serve as a biological signal that bridges neural activity and behavioral tasks, provide an innovative approach to neuroscience research. In this study, we constructed a dataset that contains over 2000 neurons across 117 days recorded in 20 mice containing 28,573 trials. Data for 5 mice were collected from the Secondary Motor Cortex (M2) region 8 mice was derived from the Ventrolateral Striatum (VLS) and 7 mice were from Substantia Nigra pars Reticulata (SNR). We induced licking behavior in head-fixed mice by periodically delivering water through a spout while simultaneously recording spiking activity from three brain regions and behavior related electrical signals. This dataset ensures precise temporal alignment between neural activity and behavioral events, offering a robust foundation for investigating neural encoding mechanisms and simulation of neural activities. This dataset establishes a precise spike-to-event mapping, which enables high decoding accuracy using Multilayer Perceptron (MLP) and Support Vector Machine (SVM). It can serve as a high-quality benchmark for developing encoding and decoding algorithms in neural networks, particularly Spiking Neural Networks (SNNs).

neuroscience↗

bioRxiv2026

Modular organization and selective motifs in the insula provide structural priors for efficient learning

The insular cortex (IC) integrates diverse sensory and interoceptive signals to support emotional and cognitive functions, exhibiting topologically functional distinctions. Although long-range pathways of the IC have been extensively mapped, the contribution of intra-IC architecture to network-level information processing remains poorly understood. Here we reconstructed single-cell projectomes of 2,267 IC neurons, generating a comprehensive cellular-resolution map of intra-IC connectivity. Graph-theoretic analyses revealed a hierarchical, topographically organized modular network with a hub-and-spoke organization and selective motif enrichment. Embedding these anatomical priors into recurrent neural network models demonstrated that intrinsic IC topology confers a distinct computational advantage: across multiple cognitive tasks, IC-initialized networks learned faster and exhibited better robustness to perturbations than those initialized with shuffled, randomized, or neighboring somatosensory cortical architectures. Together, these findings identify the IC as a structurally specialized cortical hub whose internal wiring supports efficient learning and provides design principles for brain-inspired networks.

neuroscience↗

bioRxiv2026

Role of Alanine Transaminase in Retinal Metabolic Homeostasis: Potential therapeutic target in retinal diseases

PurposeAlanine transaminases (ALT), encoded by the GPT gene, catalyzes the reversible conversion of pyruvate and glutamate to alanine and alpha-ketoglutarate, thereby correlating carbohydrate and amino acid metabolism. However, its role in the human neural retina remains unclear. This study aimed to explore the expression, localization, and metabolic function of ALT in the human neural retina and its potential involvement in retinal diseases. MethodsALT1 and ALT2 expression and localization were examined in the retinas of healthy and diabetic retinopathy (DR) donors via immunoblotting and immunofluorescence. ALT function was assessed in ex vivo human retinal explants using pharmacological inhibition with beta-chloro-L-alanine (BCLA), followed by the analyses of enzyme activity, tissue injury, and transcriptomic responses. Stable-isotope tracing with 13C-and 15N-labelled substrates combined with GC-MS was used to define ALT-dependent carbon and nitrogen fluxes in macular and peripheral retinas. Redox level (NADPH/NADP+) was also evaluated under tert-butyl hydroperoxide-induced oxidative stress. ResultsALT1 and ALT2 were both expressed in the human neural retina, with prominent localization in Muller glia and photoreceptor inner segments. ALT1 displayed a diffuse cytoplasmic distribution, whereas ALT2 demonstrated a punctate pattern consistent with mitochondrial localization. In DR retinas, ALT1 expression was spatially disorganized and heterogeneous, while ALT2 remained comparatively preserved. Inhibition of ALT with BCLA markedly reduced ALT activity without causing overt cytotoxicity or major transcriptional changes. Isotope tracing demonstrated that retinal ALT predominantly channels pyruvate-derived carbon into alanine, whereas alanine was minimally contributed to pyruvate production under basal conditions. ALT inhibition suppressed alanine synthesis and release, redirected nitrogen flux towards glutamate, glutamine, and aspartate, and uncovered distinct metabolic adaptations in macular but not peripheral retinas. Under oxidative stress, ALT inhibition induced the decrease of NADP+/NADPH ratio and LDH release, indicating improved redox balance and reduced tissue injury. ConclusionsALT is previously unrecognized as a regulator of carbon and nitrogen partitioner in the human neural retina, contributing to redox homeostasis under stress. The altered distribution of ALT1 in DR retina and the protective metabolic effects of ALT inhibition suggest ALT as a potential contributor to retinal metabolic vulnerability and a candidate therapeutic target in retinal diseases.

neuroscience↗

bioRxiv2026

Evaluating splicing factor and kinase network crosstalk through global phosphoproteomics

Both splicing and kinase signaling are biochemical processes that fundamentally determine and shape cell physiology. Although there has been some indication that there is an interaction between the two - splicing can alter the availability of exons encoding kinase targets and kinases can phosphorylate splicing factors - it has yet to be established the extent to which altering splicing factor expression impacts kinase signaling networks. In this work, we implemented a data-driven analysis using ENCODE RNA-sequencing data and prior work mapping post-translational modifications onto splice events to identify candidate splice factor perturbations that show extensive alterations to phosphorylation-encoding protein products. We then replicated the ENCODE knockdown experiments and performed global phosphoproteomics for two candidates, U2AF1 and SRSF3, complementing the transcription-level data. Both knockdowns showed extensive changes in phosphorylation and kinase activities, both basally and upon receptor tyrosine kinase stimulation. U2AF1 knockdown drove decreased JNK-associated cell death signaling but elevated chromosome regulation through CSNK2A1, PLK, and EIF2AK4 activity. SRSF3 knockdown, on the other hand, led to decreased cell cycle signaling through CDK and HIPK2 but increased cytoskeletal signaling through various PAKs. In addition, we found a striking enrichment of phosphorylated splicing regulators in both knockdowns that were linked to their splicing activity, such as HNRNPC, suggesting potential feedback and crosstalk between splice factors through signaling pathway activation. Importantly, comparison of differential phosphorylation measurements from this study to mRNA expression and splicing measurements from ENCODE revealed significant knockdown-dependent protein regulation, not captured by transcriptomic measurements alone, underscoring the value of phosphoproteomic profiling after splice factor perturbations. Combined, the transcriptomics and phosphoproteomics reveal deep interconnection between the two processes that are relevant to understanding cell signaling in health and disease.

systems biology↗

bioRxiv2026

Extreme genome reduction selectively retains modular regulatory architecture in Prochlorococcus MED4: conserved transcriptional modules reveal core physiological regulatory programs

Prochlorococcus MED4 is a minimal photoautotroph whose extreme genome streamlining extends to its transcriptional regulatory architecture, yet it dominates high-light oligotrophic surface waters and drives marine carbon cycling. Despite ecological significance, MED4 remains genetically intractable, lacking molecular tools to characterize regulatory mechanisms and construct a transcriptome-wide regulatory map. To address this, we assembled an RNA-seq compendium of 253 samples, including 207 new samples capturing transcriptional responses across three classes of experiments: diverse environmental perturbations, a 24-hour circadian cycle, and phage infection. Using independent component analysis (ICA) applied to 247 quality-filtered samples, we identify 32 independently regulated gene set modules in MED4 (iModulons). By comparison, we previously identified 78 iModulons in the model cyanobacterium Synechococcus elongatus PCC 7942, revealing how dramatically genome reduction has simplified MED4s regulatory architecture. Of the 32 iModulons in MED4, 13 are conserved modules that correlate with experimentally validated transcriptional regulons in PCC 7942, identifying regulatory programs that resisted elimination under extreme selective pressure. These conserved modules reveal regulatory programs governing photosynthesis and light responses (RpaB), circadian rhythms (RpaA), and nutrient assimilation (NtcA, PhoB). Known regulator-specific DNA-binding motifs upstream of genes in conserved modules independently support their identification as regulatory targets. Notably, RpaA governs circadian rhythms through three temporally distinct modules in MED4 versus one in PCC 7942, and the RpaB photoprotection module similarly splits into two. This work uncovers the minimal regulatory core governing photosynthesis, circadian rhythms, and C/N/P metabolism in a globally critical but genetically intractable photoautotroph. This approach offers a generalizable framework for regulatory inference beyond model organisms. ImportanceThe minimal photoautotroph Prochlorococcus MED4 possesses only 28 transcriptional regulators, versus 150+ found in most cyanobacteria, reflecting a genome streamlined by billions of years of natural selection. This streamlining minimized metabolic costs, enabling MED4 to dominate nutrient-depleted oceans today. This raises a fundamental question: which regulatory programs did nature choose to keep? The answer matters, but MED4 cannot be studied by conventional genetics, placing its molecular machinery beyond direct experimental reach. Instead, we use large-scale computational methods to define groups of co-regulated genes in MED4. By comparing MED4 with a genetically tractable model cyanobacterium, we can distinguish which regulatory programs nature preserved from those it discarded. This work reveals the minimal regulatory architecture sufficient to sustain the smallest oxygenic photoautotroph on Earth. The principles uncovered here, distinguishing essential from dispensable regulatory programs in a naturally streamlined organism, inform the design of minimal photosynthetic platforms for biotechnology.

systems biology↗

bioRxiv2026

Highly Accurate Estimation of the Fold Accuracy of Protein Structural Models

BackgroundThe function of a protein is intrinsically linked to its three-dimensional fold, and deep learning has revolutionized the field by enabling high-accuracy structure prediction at an unprecedented scale. Nevertheless, the growing deployment of these predictive pipelines in drug discovery and structural biology reveals a critical bottleneck that lies in the lack of independent and rigorous estimation of model accuracy (EMA) methodologies. ResultsHere we present DeepUMQA-Global, a single-model deep learning framework for estimating accuracy of protein structure models. Our method employs a structure-sequence cross-consistency mechanism to evaluate the bidirectional compatibility between the predicted structure and the input sequence, enabling comprehensive characterization of fold accuracy. DeepUMQA-Global outperforms the self-assessment confidence scores of AlphaFold3, achieving improvements of 57.8% in Pearson correlation and 49.0% in Spearman correlation. With respect to the CASP16 retrospective benchmark, DeepUMQA-Global outperforms all single-model accuracy estimation methods that participated in CASP16 and achieves performance comparable to that of the top consensusObased methods. A lightweight consensus strategy built upon DeepUMQA-Global ranks first among all CASP16 participants, surpassing all other methods, including consensus approaches, and highlighting the strength of our method. Remarkably, DeepUMQA-Global demonstrates a strong ability to discriminate between alternative conformational states of proteins, as evidenced in the CASP unique alternative conformation protein complex target and the CoDNaS benchmark. ConclusionsOur results indicate that DeepUMQA-Global can be extended to broader protein modeling tasks, moving beyond static evaluation to offer a foundation for dynamic conformation EMA, where it accurately discriminates alternative conformational states and demonstrates reliable predictive fidelity in model accuracy estimation.

bioinformatics↗

bioRxiv2026

An anaerobic Legionellales symbiont in Anaeramoeba pumila

Anaeramoeba pumila is a free-living anaerobic amoeba and the smallest known member of the Anaeramoebae, a phylum characterized by elaborate membrane-bound symbiosomes housing sulfate-reducing bacterial symbionts. Here, we report a draft nuclear genome assembly of A. pumila LANTAAN and describe the discovery, genomic characterization, and metabolic reconstruction of Candidatus Centrionella anaeramoebae gen. nov., sp. nov., an obligate intracellular symbiont of A. pumila belonging to the order Legionellales. Ca. Centrionella is a rare anaerobic member of Legionellales, a lineage otherwise comprising aerobic intracellular pathogens. Its genome (1.52 Mbp, 1,249 genes) is highly reduced and encodes an entirely anaerobic metabolism centered on substrate-level phosphorylation, arginine fermentation, and hydrogen oxidation via a bidirectional [NiFe]-hydrogenase -- metabolic strategies that parallel those independently evolved in the distantly related Anoxychlamydiales. The complete Dot/Icm type IVB secretion system is retained and likely mediates ongoing host manipulation, including via a large repertoire of predicted effector proteins. Strikingly, Ca. Centrionella has acquired eukaryotic Rac1-like GTPase genes from its host through horizontal gene transfer, with subsequent domain shuffling and duplication, that it may use to manipulate the cytoskeleton of its host. Unlike other Anaeramoeba symbionts, Centrionella localizes to the host microtubule-organizing center rather than a symbiosome, a localization consistent with cytoskeletal anchoring strategies described in other endosymbionts. The symbiosome, present in other Anaeramoeba species, appears to have been secondarily lost in A. pumila. A co-occurring Desulfobacter sp. LANTAAN, related to symbionts of other Anaeramoebidae, likely forms a tripartite syntrophic consortium by consuming hydrogenosomal fermentation end-products and supplying vitamin B12. Together, these findings illuminate the evolutionary transition in Legionellales from aerobic pathogenesis to anaerobic mutualism, providing a new model for the origins of intracellular symbiosis.

evolutionary biology↗

bioRxiv2026

A transient signal in foveal superior colliculus neurons for jumpstarting peripheral saccadic orienting

The superior colliculus (SC) both senses the environment and orients gaze within it. While the SCs sensory and motor bursts appear qualitatively similar to each other, population activity structure in the two processing regimes (visual and motor) is very different, necessitating a hitherto unexplored rapid representational transformation, occurring on the scale of only tens of milliseconds. Here, we first show that when a planned saccade is released with a go signal, peripheral SC neurons representing the saccade target location exhibit a transient, short-latency pause right before their motor bursts eventually emerge. This pause starts within [~]50 ms from the go signal; it is stimulus-dependent; and it is significantly weaker in purely visual SC neurons than in saccade-related ones. Foveal SC neurons, on the other hand, transiently burst, and their bursts lead the peripheral neurons pauses by [~]10 milliseconds. These transient foveal bursts also lead the same foveal neurons saccade-related pauses, which are time-locked to movement generation. Remarkably, during immediate visually-guided saccade tasks, requiring a transformation from visual to motor peripheral bursts in <50-100 ms, the transient foveal SC bursts still occur, resulting in simultaneous short-latency bursting at two disparate SC loci: one foveal; and one eccentric and responding to the visual appearance of the saccade target. Our results suggest that in classic saccade tasks used to investigate visual, motor, and cognitive processes in primate brains, a transient foveal SC signal precedes peripheral saccadic orienting, and may facilitate a necessary rapid representational transformation needed for SC saccade motor bursts to ensue. SignificanceSaccade control studies often involve behavioral paradigms dissociating stimulus presentation, deliberation epochs, and "go" instructions. While the stimulus presentation, deliberation, and actual movement aspects have been well studied, the "go" phases of trials are less considered. We show that foveal superior colliculus neurons exhibit transient activity bursts at the "go" instruction for saccades, likely enabling a rapid representational transformations from a visual to a motor regime in the extrafoveal collicular neurons driving the eye movements.

neuroscience↗

bioRxiv2026

Endogenous mutational mechanisms and metabolic context shape endometrial cancer

Uterine corpus endometrial carcinoma (UCEC) is a common gynecologic malignancy with rising mortality, yet its genome-wide mutational architecture remains incompletely understood. Here we analyze deep whole-genome sequencing data from 440 UCEC tumors from The Cancer Genome Atlas, integrated with transcriptomic and clinical data, to define subtype-specific mutational processes and genomic architectures. We uncover pronounced molecular subtype-specific differences in endogenous mutational mechanisms, retrotransposition activity, structural variation, and chromosomal instability. LINE-1 retrotransposition emerges as a key contributor to genome instability in UCEC, acting as a prominent source of structural variation in copy-number stable tumors and associating with chromothripsis and ecDNA-mediated oncogene amplification in copy-number high tumors. Mutational signature SBS28 contributes significantly to mutations in POLE-deficient tumors and is strongly correlated with SBS10a and SBS10b. Mismatch repair-deficient tumors exhibit a previously unrecognized doublet base substitution signature and a defining imbalance between ID2 and ID1 indel processes, reflecting pervasive DNA template-strand replication slippage and associated with increased tumor immunogenicity. Copy-number low tumors follow a distinct low-mutagenesis evolutionary trajectory characterized by reduced replication stress, low proliferative activity, genomic stability and enrichment of SBS18 associated with oxidative damage. Notably, we identify a consistent inverse association between body mass index and tumor mutational burden in UCEC, suggesting that host metabolic state may influence fundamental cellular processes governing mutation accumulation, promoting tumor development through non-mutagenic mechanisms rather than elevated genomic instability. Together, these findings establish a mutagenesis-centric framework for UCEC that links endogenous mutational mechanisms to tumor architecture and host metabolic context, uncovering previously unrecognized subtype-specific genomic features with important implications for refined risk stratification and therapeutic strategies.

genomics↗