Biology subjects

Meyer, J.

Publications and source records attributed to Meyer, J..

At least 19 recordsLinked to original sources

bioRxiv2026

Transient interdomain interactions shape the conformational ensemble governing RNA recognition by the tandem RRMs of Sex-lethal

RNA recognition motif (RRM) proteins frequently contain multiple RNA-binding domains connected by flexible linkers, yet the contribution of transient interdomain interactions to RNA recognition remains incompletely understood. Here, we investigated the structural organization of the tandem RRMs of the Drosophila melanogaster splicing regulator Sex-lethal (Sxl) using solution NMR spectroscopy in combination with rational protein engineering, restrained docking and RNA-binding studies. Progressive extension of the native interdomain linker resulted in a gradual decrease in rotational coupling between the two RRMs and continuous chemical shift changes, demonstrating that the RNA-free protein samples a dynamic conformational ensemble rather than behaving as two independently tumbling domains. NMR-guided docking identified a compact arrangement compatible with the experimental data and suggested a transient interface partially overlapping the RNA-binding surfaces. Surprisingly, a mutant designed to weaken this interface produced the opposite effect: instead of increasing interdomain mobility, it exhibited enhanced rotational coupling while remaining natively folded, indicating a redistribution of the conformational ensemble rather than disruption of the domain architecture. Both linker extension and the mutant reduced RNA-binding affinity, and the mutant additionally diminished sequence discrimination, demonstrating that perturbations shifting the conformational equilibrium in either direction compromise RNA recognition. Together, our results demonstrate that RNA recognition by Sxl is governed not by a single apo structure but by a finely balanced conformational ensemble, and that perturbing this equilibrium in either direction compromises high-affinity and sequence-selective RNA binding.

biophysics↗

bioRxiv2026

xTracer: Integrating chromatogram and mobiligram correlations for untargeted peptide identification in SLIM-based PAMAF data

Parallel Accumulation with Mobility-Aligned Fragmentation (PAMAF) achieves near-complete ion utilization and high spectral specificity by fragmenting all mobility-separated precursors without quadrupole isolation. Leveraging the ultrahigh mobility resolution of SLIM, this quadrupole-free strategy maximizes ion utilization efficiency and offers a promising approach in mass spectrometry-based proteomics, particularly for low-abundance peptides or low-input samples. However, the unique data structure of PAMAF where precursor-fragment relationships are encoded along the mobility dimension renders it incompatible with existing peptide identification tools. Here, we present xTracer, the first untargeted peptide identification algorithm developed specifically for PAMAF data. xTracer integrates correlations across both chromatographic and mobility dimensions to associate precursor and fragment ions, reconstruct pseudo-spectra, and enable database searching using well-established DDA search engines. Applied to datasets with varying sample loads and acquisition throughputs, xTracer consistently achieved robust and reproducible peptide identifications, outperforming single-domain correlation strategies. Overall, xTracer provides a versatile and high-efficiency computational framework for reconstructing pseudo-spectra from quadrupole-free, mobility-aligned fragmentation data, enhancing the analytical power of high-resolution ion mobility (HRIM)-based proteomics.

systems biology↗

bioRxiv2026

Emergence of focal cortical hyperexcitability in the murine tetanus toxin epilepsy model

AbstractFocal epilepsies are a heterogeneous group of neurological disorders that may be caused by a large variety of underlying brain lesions. Long-term quality of life prognosis is often poor, and treatment options are limited. Despite significant progress in animal model sophistication over the past decades, a deeper understanding of epileptogenic processes on a mesoscale and microscale circuit level is needed. Here we model focal epileptogenesis in mice using single intracortical tetanus toxin injections and employ chronic in vivo two-photon and widefield calcium imaging with simultaneous EEG and behavioral video recordings ("multimodal" recordings) to follow epileptogenic changes over time. We observe a moderate increase in global brain excitability on EEG but, more strikingly, a gradual emergence of brief but intense optically recorded epileptiform events ("microseizures") that are spatially limited, peaking around 20-30 days after toxin injection and waning over the next 30 days. During these events, a majority of local neurons are recruited into extreme depolarization, yet there is considerable variability in duration and spatial coverage between events, depending on the proximity to the injection focus and the number of days elapsed since injection. Notably, EEG electrodes <3 mm from the focus typically fail to detect these events, highlighting the utility of high-resolution in vivo optical imaging for capturing all events in focal epileptogenesis. Single-cell patch clamp recordings in awake animals confirm that microseizure episodes are associated with depolarization block, during which the calcium signal remains high. Using chronic multimodal recordings, we detect an initial rise of interictal activity in local cortical networks during the first day after injection, followed by a layer-specific suppression and dysregulation of interictal spontaneous network activity in local cortical circuits preceding microseizure events, and low-level suppression when microseizures started subsiding. The chronic suppression in interictal activity is accompanied by relative hypoactivity of PV+ interneurons and concurrent hyperactivity of SOM+ interneurons. This integrated imaging-electrophysiology approach provides a powerful platform for unraveling circuit-level mechanisms of focal epilepsy and potentially for identifying and testing novel therapeutic strategies in the future.

neuroscience↗

bioRxiv2025

Markers of resilience to stony coral tissue loss disease and probiotic potential in the microbiome of the threatened coral, Orbicella faveolata

Stony coral tissue loss disease (SCTLD) is widespread within the Caribbean and affects at least 22 species of reef-building coral. Bacteria have been implicated in the etiology of SCTLD, but the community of bacteria and archaea may also contribute to SCTLD resistance. To identify potential mechanisms through which microbes contribute to SCTLD resistance, we sequenced metagenomes from 41 colonies of the threatened coral, Orbicella faveolata, in the lower Florida Keys. All colonies were fate-tracked for three to five years and disease lesions were treated with amoxicillin. By 2024, 20% were never diseased, 10% had lesions before sampling but recovered, 22% were apparently healthy but were eventually susceptible to infection, and 49% had regular repeated infections. Within the coral microbiome, diseased and yet-to-be diseased colonies exhibited higher variability in functional genes. In contrast, corals that remained unaffected or recovered had less variable microbiomes with greater abundances of vitamin and antibiotic biosynthesis, secretion system, and quorum sensing genes that may support host health and resilience to pathogens. Though on some colonies antibiotic treatments were applied repeatedly, there was no effect on the diversity of beta-lactamases, antibiotic resistance genes that may confer amoxicillin resistance. Additional potentially probiotic gene clusters for the production of antimicrobial and bioactive compounds were present in many colonies regardless of fate. Taken together, we find significant probiotic potential in the coral microbiome to armor host O. faveolata corals against SCTLD infection, which may underpin intraspecific variation in stony coral tissue loss disease resilience and susceptibility.

microbiology↗

bioRxiv2025

Multidisciplinary assessments of a potentially novel acute tissue loss disease on Florida Orbicella corals

Coral disease outbreaks are an increasingly common threat to reefs. While coral disease research is expanding rapidly, there are still monumental challenges in diagnosing and differentiating among the different diseases on a reef. We used a collaborative multidisciplinary approach to characterize a potentially novel disease affecting Orbicella faveolata colonies in the Florida Keys. We tagged and fate-tracked individual lesions for progression and cessation rates, reanalyzed in situ photographs of previously monitored corals to determine prevalence and seasonality, and assessed the efficacy of amoxicillin treatments. Samples collected from lesions as well as unaffected and healthy controls were used to examine microbiomes, assess nine coral pathological parameters via histology, and measure 19 symbiont-specific physiological metrics using transmission electron microscopy (TEM). Across all analyses, we concluded that the observed disease is unlikely to be SCTLD. Many, but not all, metrics had similarities to previous descriptions of white plague, and so we additionally conducted preliminary histology on presumed white plague samples of O. franksi for comparison. However, the dearth of quantifiable histology and TEM studies on white plague did not allow us to conclusively confirm or refute comparisons to white plague. Using the recommended coral disease nomenclature, we define this specific outbreak as "Orbicella acute tissue loss disease" (OATLD). We provide unprecedented, quantified descriptions across numerous metrics of both diseased and control colonies. We suggest that these data lay the groundwork for future efforts on this disease as well as a comprehensive set of parameters against which other diseases can be compared.

physiology↗

bioRxiv2025

Internally twin-Strep tagged CD63 for rapid and efficient isolation of engineered extracellular vesicles encapsulating functional proteins

Extracellular vesicles (EVs) are important mediators of intercellular communication. Achieving high purity of intact engineered EVs through separation from the overwhelming background of unmodified vesicles and cellular or serum-derived contaminants remains a major challenge, yet is critical for fundamental studies of EV biology and EV-based therapeutics. To address this unmet need, we applied structure-guided engineering to canonical EV tetraspanins. Focusing on CD63 and CD9, we identified sites for internal insertion of the twin-Strep tag via flexible linkers into unstructured regions of their large extracellular loops. This design retains functional properties of the scaffolds while providing a robust molecular handle enabling rapid, efficient, and selective antibody-free affinity-based isolation of intact EVs using advanced Strep technology. Fusing proteins of interest (POIs) to the C-terminus of these scaffolds, either directly or via a photoactivatable protein, allowed POI loading into the lumen of twin-Strep tagged EVs with optional optogenetic control of POI release. Proteomic analysis confirmed the high purity of captured engineered EVs with >96% of contaminants removed, enabling sensitive detection of numerous EV-associated proteins. We also report the efficient removal of contaminating virus particles resembling EVs in size and density. Purified engineered EVs successfully delivered an encapsulated fluorescent reporter into target cells, bypassing dye labeling commonly used to track EVs. We demonstrate endosomal escape of the reporter, facilitated by EV decoration with vesicular stomatitis virus glycoprotein, and cytoplasmic release upon optogenetic activation. Our toolbox may serve as a broadly applicable strategy for the efficient production of intact and highly pure engineered EVs to support potential fundamental or translational EV studies.

molecular biology↗

bioRxiv2025

Local differences in baseline sodium shape astrocytic potassium uptake by the NKA

Astrocytes are vital for the maintenance of ion and transmitter homeostasis in the extracellular space, with the inward Na gradient playing a pivotal role in these processes. Earlier studies not only reported a low baseline Na+ concentration ([Na+]) in astrocytes, but also suggested an equilibration of [Na+] within the gap-junction-coupled syncytium. This is consistent with the view that the basic homeostatic properties of astrocytes are largely identical due to their critical role in brain function. Here, we used multi-photon fluorescence lifetime imaging for a quantitative determination of astrocytic [Na+] in mouse forebrain tissue slices and in vivo. Contrary to the prevailing notion of a rather uniform Na distribution, we detected a previously unobserved subcellular and cellular heterogeneity in astrocytic [Na+], accompanied by differences in the capacity for Na+/K+-ATPase (NKA)-mediated uptake of extracellular K+. Biophysical modelling showed that this heterogeneity can be replicated by the reported differential expression of NKA isoforms in astrocytes together with a different strength of Na+ influx over the plasma membranes. Altogether, our results thus suggest the existence of functionally distinct astrocytes and astrocyte subdomains in which Na+ homeostasis is locally adapted to the specific requirements of surrounding neural networks.

neuroscience↗

bioRxiv2025

Inhibition of Mitochondrial Complex III Causes Dopaminergic Neurodegeneration by Redox Stress in Caenorhabditis elegans

Environmental factors including chemical exposures are important contributors to Parkinsons disease (PD). Nearly all well-validated chemicals involved in PD affect mitochondria, and the great majority of those identified inhibit mitochondrial complex I, causing ATP depletion and oxidative stress. We hypothesized that inhibition of mitochondrial complex III would also cause dopaminergic neurotoxicity. Using Caenorhabditis elegans to evaluate the in vivo effects of complex III-inhibiting pesticides antimycin A and pyraclostrobin, we found that both caused selective dopaminergic neurotoxicity. We evaluated exacerbation of dopaminergic neurotoxicity by the presence of -synuclein, and pdr-1/PRKN and pink-1/PINK1 mutant backgrounds and found increased neurotoxicity for pdr-1. Complex III inhibition caused a more-oxidized cellular environment in those neurons and pharmacological and genetic antioxidant interventions rescued neurotoxicity, but energetic rescue attempts did not. Finally, optogenetic production of superoxide anion specifically at complex III caused dopaminergic neuronal damage. Thus, redox stress at complex III following chemical exposure causes dopaminergic neurotoxicity in vivo in C. elegans.

pharmacology and toxicology↗

bioRxiv2025

Spatio-temporal dynamics of lateral Na+ diffusion in apical dendrites of mouse CA1 pyramidal neurons

Sodium ions (Na+) are major charge carriers mediating neuronal excitation and play a fundamental role in brain physiology. Glutamatergic synaptic activity is accompanied by large transient Na+ increases, but the spatio-temporal dynamics of Na+ signals and properties of Na+ diffusion within dendrites are largely unknown. To address these questions, we employed multi-photon Na+ imaging combined with whole-cell patch-clamp in dendrites of CA1 pyramidal neurons in tissue slices from mice of both sexes. Fluorescence lifetime microscopy revealed a dendritic baseline Na+ concentration of ~10 mM. Using intensity-based line-scan imaging we found that local, glutamate-evoked Na+ signals spread rapidly within dendrites, with peak amplitudes decreasing and latencies increasing with increasing distance from the site of stimulation. Spread of Na+ along dendrites was independent of dendrite diameter, order or overall spine density in the ranges measured. Our experiments also show that dendritic Na+ readily invades spines and suggest that spine necks may represent a partial diffusion barrier. Experimental data were well reproduced by mathematical simulations assuming normal diffusion with a diffusion coefficient of [Formula]. Modeling moreover revealed that lateral diffusion is key for the clearance of local Na+ increases at early time points, whereas when diffusional gradients are diminished, Na+/K+-ATPase becomes more relevant. Taken together, our study thus demonstrates that Na+ influx causes rapid lateral diffusion of Na+ within spiny dendrites. This results in an efficient redistribution and fast recovery from local Na+ transients which is mainly governed by concentration differences. Significance statementActivity of excitatory glutamatergic synapses generates large Na+ transients in postsynaptic cells. Na+ influx is a main driver of energy consumption and modulates cellular properties by modulating Na+-dependent transporters. Knowing the spatio-temporal dynamics of dendritic Na+ signals is thus critical for understanding neuronal function. To study propagation of Na+ signals within spiny dendrites, we performed fast Na+ imaging combined with mathematical simulations. Our data shows that normal diffusion, based on a diffusion coefficient of 600 {micro}m2/s, is crucial for fast clearance of local Na+ transients in dendrites, whereas Na+ export by the Na+/K+-ATPase becomes more relevant at later time points. This fast diffusive spread of Na+ will reduce the local metabolic burden imposed by synaptic Na+ influx.

neuroscience↗

bioRxiv2025

Specialized high-capacity mitochondria fuel cell invasion

Cell invasion through basement membrane (BM) is energetically intensive, and how an invading cell produces high ATP levels to power invasion is understudied. By generating 20 endogenously tagged mitochondrial proteins, we identified a specialized mitochondrial subpopulation within the C. elegans anchor cell (AC) that localizes to the BM breaching site and generates elevated ATP to fuel invasion. These ETC-enriched high-capacity mitochondria are compositionally unique, harboring increased protein import machinery and dense cristae enriched with ETC components. High-capacity mitochondria emerge at the time of AC specification and depend on the AC pro-invasive transcriptional program. Finally, we show that netrin signaling through a Src kinase directs microtubule polarization, which facilitates metaxin adaptor complex dependent ETC-enriched mitochondrial trafficking to the AC invasive front. Our studies reveal that an invasive cell produces high ATP by generating and localizing high-capacity mitochondria. This might be common strategy used by other cells to meet energy demanding processes.

cell biology↗

bioRxiv2025

Real-time tracking of mRNP complex assembly reveals various mechanisms that synergistically enhance translation repression

Protein biosynthesis must be highly regulated to ensure proper spatiotemporal gene expression and thus cellular viability. Translation is often modulated at the initiation stage by RNA binding proteins through either promotion or repression of ribosome recruitment to the mRNA. However, it largely remains unknown how the kinetics of mRNA ribonucleoprotein (mRNP) assembly on untranslated regions (UTRs) relates to its translation regulation activity. Using Sex-lethal (Sxl)-mediated translation repression of msl-2 in female fly dosage compensation as a model system, we show that different mechanisms in mRNP assembly synergistically achieve tight translation repression. Using multi-color single-molecule fluorescence microscopy we show that 1) Sxl targets its binding sites via sliding and double-binding, 2) that Unr recruitment is accelerated over 500-fold by RNA-bound Sxl and 3) that Hrp48 further stabilizes RNA-bound Sxl indirectly via ATP-independent RNA remodeling. Overall, we provide a framework to study how multiple RBPs dynamically cooperate with RNA to achieve function.

biophysics↗

bioRxiv2025

Super-resolution compatible DNA labeling technique reveals chromatin mobility and organization changes during differentiation

Chromatin dynamics play a crucial role in cellular differentiation, yet tools for studying global chromatin mobility in living cells remain limited. Here, we developed a novel probe for the metabolic labeling of chromatin and tracking its mobility during neural differentiation. The labeling system utilizes a newly developed silicon rhodamine-conjugated deoxycytidine triphosphate (dCSiRTP). We show that this dCTP is efficiently delivered into living human induced pluripotent stem cells (iPSCs) and neural stem cells (NSCs) via a synthetic transporter (SNTT1). Using correlative confocal microscopy and stimulated emission depletion (STED) super-resolution microscopy, we quantified the sizes of labeled chromatin domains. Time lapse super-resolution microscopy combined with single particle tracking revealed that chromatin mobility decreases during the transition from iPSCs (pluripotent state) to NSCs and neurons (differentiated state). This reduction in mobility correlates with the differentiation state, suggesting a role for chromatin dynamics in cellular plasticity. Concomitant mechanistic insights obtained from MNase digestion assays, chromatin compaction and histone modification analyses revealed a decrease in chromatin accessibility during neuronal differentiation, indicating that chromatin adopts a more constrained and compacted structure. These findings provide new insights into chromatin regulation during neurogenesis.

cell biology↗

bioRxiv2025

Mitophagy at the oocyte-to-zygote transition promotes species immortality

The quality of inherited mitochondria determines embryonic viability1, metabolic health during adulthood and future generation endurance. The oocyte is the source of all zygotic mitochondria2, and mitochondrial health is under strict developmental regulation during early oogenesis3-5. Yet, fully developed oocytes exhibit the presence of deleterious mitochondrial DNA (mtDNA)6,7 and mitochondrial dysfunction from high levels of endogenous reactive oxygen species8 and exogenous toxicants9. How fully developed oocytes prevent transmission of damaged mitochondria to the zygotes is unknown. Here we discover that the onset of oocyte-to-zygote transition (OZT) developmentally triggers a robust and rapid mitophagy event that we term mitophagy at OZT (MOZT). We show that MOZT requires mitochondrial fragmentation, activation of the macroautophagy system and the mitophagy receptor FUNDC1, but not the prevalent mitophagy factors PINK1 and BNIP3. Oocytes upregulate expression of FUNDC1 in response to diverse mitochondrial insults, including mtDNA mutations and damage, uncoupling stress, and mitochondrial dysfunction, thereby promoting selection against damaged mitochondria. Loss of MOZT leads to increased inheritance of deleterious mtDNA and impaired bioenergetic health in the progeny, resulting in diminished embryonic viability and the extinction of descendent populations. Our findings reveal FUNDC1-mediated MOZT as a mechanism that preserves mitochondrial health during the mother-to-offspring transmission and promotes species continuity. These results may explain how mature oocytes from many species harboring mutant mtDNA give rise to healthy embryos with reduced deleterious mtDNA.

cell biology↗

bioRxiv2025

Assessment of developmental neurotoxicology-associated alterations in neuronal architecture and function using Caenorhabditis elegans

Few of the many chemicals that regulatory agencies are charged with assessing for risk have been carefully tested for developmental neurotoxicity (DNT). To speed up testing efforts, as well as to reduce the use of vertebrate animals, great effort is being devoted to alternate laboratory models for testing DNT. A major mechanism of DNT is altered neuronal architecture resulting from chemical exposure during neurodevelopment. Caenorhabditis elegans is a nematode that has been extensively studied by neurobiologists and developmental biologists, and to a lesser extent by neurotoxicologists. The developmental trajectory of the nervous system in C. elegans is easily visualized, normally entirely invariant, and fully mapped. Therefore, we hypothesized that C. elegans could be a powerful in vivo model to test chemicals for the potential to alter developmental patterning of neuronal architecture. To test whether this might be true, we developed a novel C. elegans DNT testing paradigm that includes exposure throughout development, examines all major neurotransmitter neuronal types for architectural alterations, and tests behaviors specific to dopaminergic, cholinergic, and glutamatergic functions. We used this paradigm to characterize the effects of early-life exposures to the developmental neurotoxicants lead, cadmium, and benzo(a)pyrene (BaP) on dopaminergic, cholinergic, and glutamatergic architecture. We also assessed whether exposures would alter neuronal specification as assessed by expression of reporter genes diagnostic of specific neurotransmitters. We identified no cases in which the apparent neurotransmitter type of the neurons we examined changed, but many in which neuronal morphology was altered. We also found that neuron-specific behaviors were altered during C. elegans mid-adulthood for populations with measured morphological neurodegeneration in earlier stages. The functional changes were consistent with the morphological changes we observed in terms of type of neuron affected. We identified changes consistent with those reported in the mammalian DNT literature, strengthening the case for C. elegans as a DNT model, and made novel observations that should be followed up in future studies.

pharmacology and toxicology↗

bioRxiv2024

Two methodologies and timescales show no promotion of antibiotic resistance from in-water coral disease treatments

The decimation of reefs caused by stony coral tissue loss disease prompted the use of a topical amoxicillin treatment to prevent coral mortality. Application of this treatment led to concerns about unintentional impacts such as potential alteration of the coral microbiome and possible spread of antibiotic resistance. We used two different methodologies - microbial RNA sequencing and microbial qPCR array - to assess these concerns and to establish a baseline of antimicrobial resistance genes in coral microbes. RNA sequencing was conducted on coral mucus samples collected before and 24 hours after amoxicillin application on wild Montastraea cavernosa. While diverse antibiotic resistance genes (ARGs) were expressed, no differences were detected in ARG expression after amoxicillin treatment. Additionally, there were no notable changes in the microbial communities between the before and after samples. Microbial qPCR array was used to assess differences in ARGs over longer timescales in wild Colpophyllia natans, comparing never-treated corals with ones treated a single time seven months prior and with those treated multiple times seven months and more prior. No clinically relevant ARGs represented in the arrays were detected across any samples. A small number of above-detection reads (4 in the never-treated corals, 2 in the once-treated corals, and 0 in the multi-treated corals) may indicate weak amplification of similar environmental (non-anthropogenic) ARGs in the corals. Results indicate that the localized topical application of amoxicillin to prevent mortality of SCTLD-affected corals is neither immediately disrupting the microbiome of treated corals at the colony level nor driving the development of ARGs over immediate or longer-term time scales.

microbiology↗

bioRxiv2024

A novel epigenetic clock for rhesus macaques unveils an association between early life adversity and epigenetic age acceleration

Because DNA methylation changes reliably with age, machine learning models called epigenetic clocks can estimate an individuals age based on their DNA methylation profile. This epigenetic measure of age can deviate from ones true age, and the difference between the epigenetic age and true age, known as epigenetic age acceleration (EAA), has been found to directly correlate with morbidity and mortality in adults. Emerging evidence suggests that EAA is also associated with aberrant health outcomes in children, making epigenetic clocks useful tools for studying aging and development. We developed two highly accurate epigenetic clocks for the rhesus macaque, utilizing 1,008 blood samples from 690 macaques between 2 days and 23.4 years of age with diverse genetic backgrounds and exposure to environmental conditions. The first clock, which is trained on all samples, achieves a Pearson correlation between true age and predicted age of 0.983 and median absolute error of 0.210 years. To study phenotypes during development, the second clock is optimized for macaques younger than 6 years and achieves a Pearson correlation of 0.974 and a median absolute error of 0.148 years. Using the latter clock, we investigated whether epigenetic aging is affected by early life adversity in the form of infant maltreatment. Our data suggests that maltreatment and increased hair cortisol levels are associated with epigenetic age acceleration right after the period of maltreatment.

neuroscience↗

bioRxiv2024

Structure of the virulence-associated Neisseria meningitidis filamentous bacteriophage MDA{varphi}

Neisseria meningitidis is a human commensal bacterium that can opportunistically invade the bloodstream and cross the blood-brain barrier, where it can cause septicaemia and meningitis. These diseases, if left untreated, can be lethal within hours. Hyperinvasive N. meningitidis strains often express a genomically encoded filamentous bacteriophage called MDA{Phi}, which promotes colonisation of mucosal host surfaces to facilitate invasion. How this phage is organised and how it promotes biofilm formation and infection at the molecular level is unclear. Here, we present an electron cryomicroscopy structure of the MDA phage, showing that MDA{Phi} is a class I filamentous inovirus, with the major capsid protein arranged within the phage as a highly curved and densely packed -helix. Comparison with other filamentous bacteriophages offers clues about inoviral genome encapsidation mechanisms, providing a framework for understanding the evolutionary diversity of inoviruses. A disordered, N-terminal segment in the major capsid protein presents hydrophobic patches on the surface of assembled phage particles, which, together with electron cryotomography data of phage bundles, furnishes a structural rationale for phage-phage interactions that were seen previously in an epithelium adhesion infection model of N. meningitidis. Taken together, our results shed light on the structure, organisation, and higher order assembly of a biomedically relevant phage encoded in the genome of a human pathogen. Molecular insights gleaned from this study increase our understanding of phage evolution, phage-mediated bacterial adhesion and pathogenicity.

microbiology↗

bioRxiv2024

Morphology-dependent entry kinetics and spread of influenza A virus

Influenza A viruses (IAV) display a broad variety of morphologies ranging from spherical to long filamentous virus particles. These diverse phenotypes are believed to allow the virus to overcome various immunological and pulmonary barriers during entry into the airway epithelium and influence the viral entry pathway. Remarkably, lab-adapted IAV strains lost this morphological variance and exhibit preferred spherical morphology. However, it remains unclear which factors lead to this lab-adapted preference and which pulmonary defense factors are responsible for the preferred filamentous morphology in physiological settings. In this study, we established fluorescent reporter viruses with spherical or filamentous morphology but with the same surface glycoproteins. We developed a correlative fluorescence and scanning electron microscopy workflow to analyze the impact of viral morphology on cell-to-cell spread and identify conditions under which IAV with either spherical or filamentous morphology confer an advantage. Our findings demonstrate that filamentous IAV cell-to-cell spread is significantly slower in various cell lines, which can explain the predominant spherical morphology in lab-adapted strains. This observation is consistent with delayed entry kinetics of filamentous viruses structurally analyzed by cellular cryo-electron tomography. We found that cellular junction integrity and mucin do not exert morphology-dependent inhibition of IAV cell-to-cell spread. On the other hand, filamentous virions confer an advantage under the pressure exerted by neutralizing antibodies against hemagglutinin.

microbiology↗