Biology subjects

Coleman, M.

Publications and source records attributed to Coleman, M..

At least 19 recordsLinked to original sources

bioRxiv2026

Isolation and characterisation of Lytic Jumbo Klebsiella phage BMPCR_005026

Background: Klebsiella pneumoniae is a key causative agent of multidrug resistant nosocomial infections. Bacteriophages offer a promising alternative treatment, but the diversity of Klebsiella species requires the characterisation of a broad range of phages, particularly the poorly characterised jumbo phages. Materials and Methods: Phage BMCPR_005026 was isolated from sewage against Klebsiella pneumoniae. Whole genome sequencing, transmission electron microscopy and host range analysis against a diverse set of 40 clinically relevant Klebsiella strains were used to characterise the phage. Results: The virion had a myovirus morphology and genomic analysis placed it within an undefined family in Caudoviricetes where it forms a new species within the genus Alcyoneusvirus. BMCPR_005026 could form plaques on 3 of the 40 Klebsiella strains tested (7.5%) and formed halos. Conclusion: BMCPR_005026 represents a new species of phage within the genus Alcyoneusvirus with activity against 3 Klebsiella KL-types.

microbiology↗

bioRxiv2026

Characterization of Resolved, Localized, and Progressing Infections at the Maternal-Fetal Interface in a Nonhuman Primate Model

Background: Inflammation and infection are responsible for the majority of early preterm births. Host innate immune responses at the maternal-fetal interface that contribute to sterile intra-amniotic inflammation (SIAI), bacterial clearance, or invasive infection remain poorly understood. Group B Streptococcus (Streptococcus agalactiae) is a leading cause of preterm birth, stillbirth, and invasive neonatal disease. Objective: To determine the host innate immune factors and transcriptional profiles that characterize the persistence versus resolution of a Group B Streptococcus infection at the maternal-fetal interface in a nonhuman primate (pigtail macaque, Macaca nemestrina) model. We hypothesized that a highly inflammatory profile, associated with interleukin-1 signaling, is linked to progression, whereas a mild or non-inflammatory signature is associated with infection resolution. Study Design: In a chronically catheterized pregnant pigtail macaque model, Group B Streptococcus was inoculated into the choriodecidual space. Infections were classified as progressing (invasive into the amniotic fluid), localized (bacteria persisting at the inoculation site), or resolved (minimal to no bacteria detected). Temporal and spatial RNA and protein profiles in the chorioamniotic membranes and decidua and in the myometrium were assessed by histopathology, multiplex protein assays, total RNA-sequencing, Nanostring nCounter, and spatial transcriptomics (digital spatial profiling). Differential gene expression was analyzed with limma using moderated t-tests and by gene set enrichment analysis. Results: A GBS infection at the maternal-fetal interface produced three infection outcomes: progressing infections that disseminated into the amniotic fluid (AF, N=5), low-titer localized infections remaining at the inoculation site (N=6), and resolved infections (N=5), compared with saline controls (N=3). Preterm labor occurred frequently regardless of infection outcome (40-80%). In resolved infections, SIAI occurred in the AF and lymphocytes infiltrated the myometrium. Total RNA-Seq of the chorioamniotic membranes demonstrated that 99 genes separated progressing from resolved infections, 98 of them were upregulated and dominated by IL-1 signaling and granulocyte recruitment (i.e., IL1B, CXCL8, TLR2, CLEC4A). Histone deacetylase 10 (HDAC10) was the only significantly downregulated gene in the progressing versus resolved contrast (p<0.05). An exploratory spatial transcriptomics experiment localized the progressing inflammatory response to the chorion. In the myometrium, zinc and RING finger 3 (ZNRF3) was significantly downregulated in localized versus control and resolved versus control and was also the only differentially expressed gene. Downregulated WNT signaling and upregulated lymphocyte-mediated immunity gene sets in the myometrium were a signature of resolved infections. Conclusion: A GBS infection at the maternal-fetal interface can result in a spectrum of progressing, localized and resolved outcomes. An early IL-1 and granulocyte response in the chorion layer of the chorioamniotic membranes marks bacterial dissemination, with loss of HDAC10 suggesting epigenetic regulation within the membranes with progressing infections. In the myometrium, ZNRF3 and downregulation of WNT signaling persisted even after infection resolution, reflecting an infectious exposure. Unexpectedly, resolved infections were associated with SIAI and a myometrial inflammatory response, offering a possible explanation for preterm labor associated with SIAI.

systems biology↗

bioRxiv2026

Widespread phages exhibit depth-structured infection coupled with ammonia oxidation

Ammonia oxidation is a rate-limiting step in the nitrogen cycle, yet viral contributions to this process remain largely unresolved. Here, we identify three genomically distinct groups of amoC-encoding phages (155-338 kilobases in length; termed as amoC-phages) from multiple freshwater lakes in Europe and North America, including the Laurentian Great Lakes. These phages are highly divergent in phylogeny, genome architecture, and gene content, and are predicted to infect two distinct Nitrosomonadaceae ammonia-oxidizing bacterial lineages. The placement of phage-encoded amoC genes across these divergent viral clades indicates independent acquisition of amoC. Time-series and depth-resolved metagenomes and metatranscriptomes reveal persistent and depth-structured distributions of amoC-phages and their predicted hosts, with seasonal mixing periodically reshaping their co-occurrence patterns. Furthermore, virome data from Lake Mendota show that some of the amoC-phages occur as free viral particles, supporting active viral lysis and particle redistribution along the water column. Metatranscriptomes of the Laurentian Great Lakes reveal coordinated expression of phage structural genes (e.g., major capsid protein) together with phage-encoded amoC, indicating active infection in situ. Together, these results support a framework in which amoC-phage infection is depth-structured, seasonally dynamic, and coupled to ammonia-oxidizing bacterial host activity, highlighting viruses as previously overlooked components of freshwater nitrogen cycling.

microbiology↗

bioRxiv2026

Fluorescence correlation spectroscopy measurements of the chlamydia outer protein B (CopB) made by cell-free protein synthesis

We demonstrate the use of fluorescence correlation spectroscopy (FCS) to characterize fluorescently-labeled protein production. We use cell-free protein synthesis to express the protein YFP-CopB, a fusion of Chlamydia Outer Protein (Cop) B and Yellow Fluorescent Protein (YFP). CopB is a [~]50 kDa protein believed to have a critical role in chlamydial infection.1 After adding a plasmid encoding YFP-CopB to an E. coli cell-free lysate, protein expression begins. We track the cell-free reaction over several hours using the EI-FLEX, a commercial instrument with FCS capability. As protein is expressed over time, YFP-CopB increases in concentration, and the EI-FLEX detects an increase in fluorescent signal above the background of the cell-free lysate. The FCS data collected gives information about the size, aggregation tendencies, rates of production and fluorescent protein maturation, and concentration of the YFP-CopB produced. The use of FCS concurrent with cell-free synthesis presents a simple method to characterize proteins of interest as they are produced without the need for purification.

biophysics↗

bioRxiv2026

Topic modeling reveals thermally partitioned and taxonomically distinct microbial subcommunities across prokaryotes and phytoplankton in the Laurentian Great Lakes

Identifying discrete microbial assemblages and their environmental drivers across multiple biological fractions simultaneously remains a central challenge in aquatic microbial ecology. We applied an integrated analytical pipeline built around Latent Dirichlet Allocation (LDA) to an eight-year 16S rRNA amplicon time series from the Laurentian Great Lakes, spanning four size-fractionated biological blocks -- free-living prokaryotes, particle-associated prokaryotes, and small and large chloroplast-containing eukaryotes. LDA resolved ecologically coherent subcommunities whose taxonomic identity was consistently defined at the order and class level, with fingerprint taxa confirmed by discriminant analysis. Shannon entropy differences between blocks reflected fundamental differences in dispersal capacity and environmental filtering -- free-living prokaryotes and large eukaryotes showed higher mixing than particle-associated prokaryotes and small eukaryotes. Temperature dominated environmental structuring across all blocks, assessed through Limma and random forest with SHAP, with secondary drivers differing by size fraction. Group Compositional Analysis jointly integrating all four blocks revealed that thermal stratification and lake chemistry organize microbial communities coherently across all size fractions simultaneously. Warm stratified and cold inversely-stratified waters harbored largely non-overlapping assemblages across all four blocks, with cold water specialists -- including chemolithotrophic deep-branching lineages and silica-dependent diatoms -- having no warm water equivalents. ImportanceThe Laurentian Great Lakes are among the fastest warming lakes in the world, yet the microbial communities that drive their biogeochemical cycles remain poorly characterized across size fractions and thermal habitats. Using eight years of samples spanning all five Great Lakes, we show that free-living bacteria, particle-associated bacteria, small phytoplankton, and large phytoplankton all respond coherently to the same master environmental gradients -- thermal stratification and lake chemistry -- despite fundamental differences in organism size, trophic role, and sequencing protocol. Warm stratified and cold water habitats support distinct microbial communities, and the cold water specialists identified here have no warm water equivalents. As the Great Lakes warm and cold water habitats shrink, the microbial communities that depend on them will not simply become less abundant they will be replaced by fundamentally different assemblages.

microbiology↗

bioRxiv2026

A single-cell transcriptomic atlas of the periventricular proliferative zone in the late gestation fetal brain in the pigtail macaque

BackgroundThe fetal brain undergoes rapid changes in late gestation, when waves of neurogenesis and gliogenesis shape cortical circuitry. The periventricular proliferative region and adjacent white matter are enriched in neuroprogenitor cells, newborn neurons, and interneurons, which is challenging to study in the late gestation human fetal brain. The nonhuman primate (NHP) provides a powerful translational model to overcome this limitation, given its close similarity to human neurodevelopmental trajectories. The study objective was to construct a single-cell RNA-Seq (scRNA-Seq) atlas of the late-gestation fetal brain of the pigtail macaque (Macaca nemestrina), focused on the periventricular proliferative zone. MethodsA sample of the lateral ventricular wall, subventricular zone, and overlying white/gray matter was dissociated into single cells and processed through the 10X Genomics pipeline, followed by SoupX removal of ambient RNA, and Seurats pipeline to aggregate, cluster and annotate single-cell populations. Monocle3 was used to determine pseudotime and map lineage progression. ResultsThis analysis captured diverse populations of neuroprogenitors, newborn neurons, developing lineages of excitatory and inhibitory neurons, oligodendrocyte and astrocyte lineages, and resident immune and endothelial cells. ConclusionsSingle-cell populations from the third-trimester nonhuman primate fetal brain are highly similar to those in the human fetus. This late-gestation single-cell atlas of the periventricular proliferative zone provides a unique reference for progenitor, neuronal, glial, vascular, and immune cell states during a critical window of primate neurodevelopment, enabling mechanistic interrogation of how inflammatory, infectious, or hypoxic insults disrupt vulnerable neurogenic niches.

genomics↗

bioRxiv2025

Inactivation of a protein hydroxylase complex impairs replication fork restart in cancer and neurodevelopmental disorders

Protein hydroxylation is a post-translational modification that is commonly catalysed by enzymes of the oxygen- and 2-oxoglutarate (2OG)-dependent oxygenase family. The Jumonji-C (JmjC)-only sub-family of 2OG-oxygenases catalyse the hydroxylation of protein and tRNA substrates involved in fundamental cellular processes. Jumonji-domain 5 (JMJD5) is a highly conserved and essential 2OG-oxygenase that, thus far, is the only arginyl hydroxylase assigned in eukaryotes. We recently reported that JMJD5 hydroxylase activity is required for DNA replication fidelity, and that pathogenic variants cause replication stress (RS) and genome instability (GIN) in a novel neurodevelopmental disorder. Because of the prevalence of RS and GIN in cancer, and reported roles of JMJD5 in tumorigenesis, we here investigate the impact of JMJD5 cancer mutations on its role in replication fidelity. We describe the structural impact of cancer missense mutations on the hydroxylase activity of JMJD5 and its interaction with RCCD1, an abundant binding partner encoded by a gene associated with susceptibility to a variety of tumour types. We show that the JMJD5:RCCD1 interaction is disrupted by cancer mutations and that the complex is essential for suppressing RS and GIN in tumour cells. Finally, we describe a novel interaction of the complex with RAD51 paralogues and demonstrate the importance of the JMJD5:RCCD1 interaction for normal replication fork restart. Our findings further highlight the importance of protein hydroxylases in fundamental cellular processes and the consequences of JMJD5 and RCCD1 deregulation in human disease.

cancer biology↗

bioRxiv2025

Tau oligomers can occur in human brains within days of a single traumatic brain injury

Traumatic brain injury (TBI) is a major risk factor for Alzheimers disease (AD), yet the early molecular events linking the two remain unclear. Neurofibrillary tangles (NFTs), a hallmark of AD, are observed in individuals with a history of single or repetitive head injury. Animal studies show that tau oligomers, the toxic species preceding the NFTs, appear shortly after TBI, but corresponding human data are lacking. Here, we investigated tau changes in the brains of individuals who died shortly after TBI compared to those surviving long-term. We report abnormal tau oligomers in the brain of short-term survivors whereas NFTs were the main feature in long-term survivors. These findings support a model where TBI triggers early tau oligomers formation that spread through a prion-like mechanism, seeding tau pathology and contributing to late-onset AD. The novel identification of tau oligomers in acute TBI reveals potential early disease mechanisms and therapeutic targets for AD prevention. Importance statementBy revealing a potential early disease mechanism of Alzheimers disease (AD), this study represents a major breakthrough in our understanding, treatment and prevention of the disease. To our knowledge, this is the first report of tau oligomers in the brain of individuals suffering acute Traumatic Brain Injury (TBI). This is an important finding considering that TBI is a major risk factor of AD and tau oligomers are thought to be the most toxic species preceding tau pathology, a characteristic signature of AD. The identification of these early tau-related events after TBI provides insight into potential early AD mechanisms and offers a unique opportunity for early therapeutic intervention and prevention.

neuroscience↗

bioRxiv2025

Rolling out plaque-2-sequence: a single plaque sequencing approach enabling rapid, low-cost sequencing of phages directly from plaques

Rapid, accurate, and scalable sequencing of bacteriophage genomes is critical to advance phage therapy, build phage biobanks and understand phage genomic diversity. Current methods are based on sequencing and assembling complete bacteriophage genomes using short- or long-read technologies. However, current protocols require large DNA input and are cost prohibitive which limits their application to phage collections that typically are large and have low-biomass. In order to address this we have developed plaque-2-sequence, a robust and cost-effective workflow for high-throughput phage genome sequencing that will transform the speed and cost of attaining phage genomes. Plaque-2-sequence combines low-input transposase-based library preparation, amplification, nanopore sequencing and optimised assembly steps tailored to phage genomes. We applied the method to phages isolated on seven genetically diverse bacterial hosts; Escherichia, Pseudomonas, Synechococcus, Enterococcus, Klebsiella , Serratia and Enterobacter. High quality genome assemblies were validated using CheckV and benchmarking against previously sequenced phage isolates. Compared to standard Illumina sequencing, plaque-2-sequence offers [~]10-fold savings in sequencing price for individual labs. Furthermore, it substantially decreases the time required to produce a phage genome, once a plaque is obtained. Offering the ability to routinely obtain hundreds of phage genome sequences a week, with minimal hands-on time. Plaque-2-sequence enables systematic genomic characterisation of phage isolates, facilitating taxonomic classification, for the development of large scale phage biobanks. Impact StatementHere we have optimised a method for high-throughput sequencing of bacteriophage genomes from single plaques (plaque-2-sequence). We present a robust, high-throughput and cost-effective workflow. Plaque-2-sequence combines low-input transposase-based library preparation, amplification, nanopore sequencing and optimised assembly steps tailored to phage genomes. We demonstrate the scalability of this approach by sequencing over 100 phages from multiple bacterial hosts. This marks a step-change for the field, allowing phage genome sequencing to keep pace with phage isolation rates, and transforming how rapidly we can explore and understand phage genomic diversity.

microbiology↗

bioRxiv2025

Maternal Influenza A Virus Infection Induces Antiviral and Immune Dysregulation in the Placenta and Fetus Without Vertical Transmission

Influenza A virus (IAV) infection during pregnancy is associated with stillbirth and preterm birth, but the degree to which IAV alters placental and fetal immunity is poorly understood. The objective of our study was to determine the immunologic impact of maternal IAV infection on the placenta and fetus in a pigtail macaque (Macaca nemestrina) model. Pregnant pigtail macaques were inoculated with 107 plaque forming units (PFU) of IAV [A/California/07/2009 (H1N1)] and underwent necropsy 5 days post-infection (N=11). Results were compared to uninfected historical controls (N=16). IAV inoculation induced maternal pneumonia in all cases. Stillbirth occurred in 18% (2/11) of IAV-infected pregnancies, but not in controls. While vertical transmission was not observed, low-level IAV viral RNA was detected in two placentas. In the placenta, maternal IAV infection was associated with increased IL-1{beta}, IL-18, and IFN-{beta} levels, and an upregulated type I interferon (IFN) transcriptional response. IAV infection was also associated with significantly higher frequencies of intermediate and non-classical monocytes, plasmacytoid dendritic cells, CD4 T cells, and NKT cells in the fetus (lung, lymph node, blood). Although placental immune and transcriptional perturbations were rarely correlated with maternal IAV disease indicators (e.g., maternal lung viral load/IFN-/IFN-{beta}/IL-6), there were consistent and significant correlations between these metrics and perturbed immune cell populations in the fetus (CD4+ and CD8+ T cells, plasmacytoid dendritic cells, monocyte sub-populations). Maternal IAV infection disrupted both placental and fetal immune environments, but only fetal immune alterations correlated with maternal lung disease severity. One Sentence SummaryMaternal influenza A virus infection in pregnant pigtail macaques dysregulates placental and fetal immunity, with disease severity correlating strongly with fetal, but not placental, immune perturbations.

systems biology↗

bioRxiv2025

A single-cell transcriptomic atlas of the pigtail macaque placenta in late gestation

The placenta is a complex organ with multiple immune and non-immune cell types that promote fetal tolerance and facilitate the transfer of nutrients and oxygen. The nonhuman primate (NHP) is a key experimental model for studying human pregnancy complications, in part due to similarities in placental structure, which makes it essential to understand how single-cell populations compare across the human and NHP maternal-fetal interface. We constructed a single-cell RNA-Seq (scRNA-Seq) atlas of the placenta from the pigtail macaque (Macaca nemestrina) in the third trimester, comprising three different tissues at the maternal-fetal interface: the chorionic villi (placental disc), chorioamniotic membranes, and the maternal decidua. Each tissue was separately dissociated into single cells and processed through the 10X Genomics and Seurat pipeline, followed by aggregation, unsupervised clustering, and cluster annotation. Next, we determined the maternal-fetal origins of cell populations and analyzed single-cell RNA trajectory, Gene Ontology enrichment, and cell-cell communication. Single-cell populations in the pigtail macaque were strikingly similar in their identity and frequency to those found in the human placenta, including cells from trophoblast, stromal cell, immune, and macrophage lineages. An advantage of our approach was the deep sequencing of three tissues at the maternal-fetal interface, which yielded a rich diversity of common and rare single-cell populations. The third-trimester pigtail macaque single-cell atlas enables the identification of cellular subclusters analogous to those in humans and provides a powerful resource for understanding experimental perturbations on the NHP placenta.

genomics↗

bioRxiv2025

Efficacy of the BiteBarrier transfluthrin emanator against susceptible and resistant malaria and arbovirus vectors in the semi-field system in Tanzania

Controlling mosquito-borne diseases is increasingly challenging due to factors such as outdoor and early biting mosquitoes and logistical or behavioral barriers, particularly in displaced populations where the use and efficacy of core interventions are inadequate. This study evaluated the impact of BiteBarrier, a transfluthrin-based spatial emanator, over eight weeks of aging against multiple mosquito species in semi-field system simulating both indoor and outdoor settings. We assessed the protective efficacy using both landing rate and feeding success methods across five mosquito species, including pyrethroid susceptible Anopheles gambiae sensu stricto (s.s.) and Aedes aegypti, An. gambiae s.s. with knock down resistance (KDR), and pyrethroid resistant An. funestus and Culex quinquefasciatus with upregulation of mixed function oxidases. The results show that the feeding endpoint provides more robust estimates of protective efficacy compared to the landing endpoint. The BiteBarrier provided over 93% (95% CI: 92 - 93) protection indoors and 80% (95% CI: 78 - 81) outdoors against mosquito bites and substantial mortality 47% (95% CI: 43 - 53) indoor and 26% (95% CI: 22 - 30) outdoors, regardless of mosquito species or resistance status. Overall, the BiteBarrier shows potential as a tool for reducing mosquito bites and vectorial capacity, offering protection over at least eight weeks of use for both indoor and outdoor environments.

systems biology↗

bioRxiv2024

Intermittent energy restriction inhibits tumor growth and enhances paclitaxel response in a transgenic mouse model of endometrial cancer

ObjectiveOverweight/obesity is the strongest risk factor for endometrial cancer (EC), and weight management can reduce that risk and improve survival. We aimed to establish the differential abilities of intermittent energy restriction (IER) and low-fat diet (LFD), alone and in combination with paclitaxel, to reverse the procancer effects of high-fat diet (HFD)-induced obesity in a mouse model of EC. MethodsLkb1fl/flp53fl/fl mice were fed high-fat diet (HFD) or LFD to generate obese and lean phenotypes, respectively. Obese mice were maintained on HFD or switched to LFD (HFD-LFD) or IER (HFD-IER). Ten weeks after induction of endometrial tumor, mice in each group received paclitaxel or placebo for 4 weeks. Body and tumor weights; tumoral transcriptomic, metabolomic and oxylipin profiles; and serum metabolic hormones and chemocytokines were assessed. ResultsHFD-IER and HFD-LFD, relative to HFD, reduced body weight; reversed obesity-induced alterations in serum insulin, leptin and inflammatory factors; and decreased tumor incidence and mass, often to levels emulating those associated with continuous LFD. Concurrent paclitaxel, versus placebo, enhanced tumor suppression in each group, with greatest benefit in HFD-IER. The diets produced distinct tumoral gene expression and metabolic profiles, with HFD-IER associated with a more favorable (antitumor) metabolic and inflammatory environment. ConclusionIn Lkb1fl/flp53fl/fl mice, IER is generally more effective than LFD in promoting weight loss, inhibiting obesity-related endometrial tumor growth (particularly in combination with paclitaxel), and reversing detrimental obesity-related metabolic effects. These findings lay the foundation for further investigations of IER as a EC prevention strategy in women with overweight/obesity.

cancer biology↗

bioRxiv2023

Adaptation of a commercial NAD quantification kit to assay the base exchange activity of SARM1

Here we report an adapted protocol using the Promega NAD/NADH-Glo Assay kit. The assay normally allows quantification of trace amounts of both oxidized and reduced forms of nicotinamide adenine dinucleotide (NAD) by enzymatic cycling, but we now show that the NAD analog 3- acetylpyridine adenine dinucleotide (AcPyrAD) also acts as a substrate. In fact, AcPyrAD generates amplification signals of larger amplitude than those obtained with NAD. We exploited this finding to devise and validate a novel method for assaying the base exchange activity of SARM1 in reactions containing NAD and an excess of the free base 3-acetylpyridine (AcPyr), where AcPyrAD is the product. We also propose an application of this method based on competition between AcPyr and other free bases to rank their preference for SARM1. This has significant advantages over traditional methods for assaying SARM1 base exchange as it is rapid, sensitive, cost-effective, and easily scalable. This could represent a useful tool given current interest in the role of SARM1 base exchange in programmed axon death and related human disorders. It may also be applicable to other multifunctional NAD glycohydrolases (EC 3.2.2.6) that possess similar base exchange activity.

biochemistry↗

bioRxiv2023

Acetyl-CoA Carboxylase Obstructs CD8+ T-Cell Lipid Utilization and Energy Synthesis in the Tumor Microenvironment

The solid tumor microenvironment (TME) imprints a compromised metabolic state in tumor infiltrating T cells (TILs) hallmarked by the inability to maintain effective energy synthesis for antitumor function and survival. T cells in the TME must catabolize lipids via mitochondrial fatty acid oxidation (FAO) to supply energy in nutrient stress, and it is established that T cells enriched in FAO are adept at cancer control. However, endogenous TILs and unmodified cellular therapy products fail to sustain bioenergetics in tumors. Using patient samples and mouse models, we reveal that the solid TME imposes perpetual acetyl-CoA carboxylase (ACC) activity, enforcing lipid biogenesis and storage in TILs that directly opposes FAO. Using metabolic, lipidomic, and confocal imaging strategies, we find that restricting ACC wholly rewires T cell metabolism, enabling energy maintenance in TME stress. Moreover, limiting ACC activity potentiates a gene and phenotypic program indicative of T cell memory, engendering TILs with increased survival and polyfunctionality, with the ability to control solid cancer.

immunology↗

bioRxiv2023

Genetically perturbed myelin as a risk factor for neuroinflammation-driven axon degeneration

Axon degeneration and functional decline in myelin diseases are often attributed to loss of myelin but their relation is not fully understood. Perturbed myelinating glia can instigate chronic neuroinflammation and contribute to demyelination and axonal damage. Here we study mice with distinct defects in the proteolipid protein 1 gene that develop axonal damage which is driven by cytotoxic T cells targeting myelinating oligodendrocytes. We show that persistent ensheathment with perturbed myelin poses a risk for axon degeneration, neuron loss, and behavioral decline. We demonstrate that CD8+ T cell-driven axonal damage is less likely to progress towards degeneration when axons are efficiently demyelinated by activated microglia. Mechanistically, we show that cytotoxic T cell effector molecules induce cytoskeletal alterations within myelinating glia and aberrant actomyosin constriction of axons at paranodal domains. Our study identifies detrimental axon-glia-immune interactions which promote neurodegeneration and possible therapeutic targets for disorders associated with myelin defects and neuroinflammation.

neuroscience↗

bioRxiv2023

Distinct axo-protective and axo-destructive roles for Schwann cells after injury in a novel compartmentalised mouse myelinating coculture system.

Myelinating Schwann cell (SC)- dorsal root ganglion (DRG) neuron cocultures have been an important technique over the last four decades in understanding cell-cell signalling and interactions during peripheral nervous system (PNS) myelination, injury, and regeneration. While methods using rat SCs and rat DRG neurons are commonplace, there are no established protocols in the field describing the use of mouse SCs with mouse DRG neurons in dissociated myelinating cocultures. There is a great need for such a protocol as this would allow the use of cells from many different transgenic mouse lines. Here we describe a protocol to coculture dissociated mouse SCs and DRG neurons and induce robust myelination. Use of microfluidic chambers permits fluidic isolation for drug treatments, allows cultures to be axotomised to study injury responses, and cells can readily be transfected with lentiviruses to permit live imaging. We used this model to quantify the rate of degeneration after traumatic axotomy in the presence and absence of myelinating SCs and axon aligned SCs that were not induced to myelinate. We find that SCs, irrespective of myelination status, are axo-protective and delay axon degeneration early on. At later time points after injury, we use live imaging of cocultures to show that once axonal degeneration has commenced SCs break up, ingest, and clear axonal debris. Summary statementA novel compartmentalised dissociated mouse myelinating SC-DRG coculture system reveals distinct axo-protective and axo-destructive phases of Schwann cells on axon integrity after trauma.

neuroscience↗

bioRxiv2022

SARM1 detection in oligodendrocytes but not Schwann cells though sarm1/Sarm1 deletion does not perturb CNS nor PNS myelination in zebrafish and mice.

SARM1 is a central regulator of programmed axon death and is required to initiate axon self-destruction after traumatic and toxic insults to the nervous system. Abnormal activation of this axon degeneration pathway is increasingly recognized as a contributor to human neurological disease and SARM1 knockdown or inhibition has become an attractive therapeutic strategy to preserve axon loss in a variety of disorders of the peripheral and central nervous system. Despite this, it remains unknown whether Sarm1/SARM1 is present in myelinating glia and whether it plays a role in myelination in the PNS or CNS. It is important to answer these questions to understand whether future therapies inhibiting SARM1 function may have unintended deleterious impacts on myelination. Here we show that Sarm1 mRNA is present in oligodendrocytes in zebrafish but only detectable at low levels in Schwann cells in both zebrafish and mice. We find SARM1 protein is readily detectable in murine oligodendrocytes in vitro and in vivo and activation of endogenous SARM1 in oligodendrocytes induces cell death. In contrast, SARM1 protein is not detectable in Schwann cells and satellite glia in the adult murine nervous system. Cultured Schwann cells contain negligible functional SARM1 and are insensitive to specific SARM1 activators. Using zebrafish and mouse Sarm1 mutants, we show that SARM1 is not required for initiation of myelination nor myelin sheath maintenance by oligodendrocytes and Schwann cells. Thus, strategies to inhibit SARM1 function in the nervous system to treat neurological disease are unlikely to perturb myelination in humans. Main PointsO_LISARM1 protein is detectable in oligodendrocytes but not in Schwann cells C_LIO_LIOligodendrocytes but not Schwann cells die in response to endogenous SARM1 activation C_LIO_LICNS nor PNS myelination, in zebrafish and mice, is hindered by loss of sarm1/Sarm1 C_LI

neuroscience↗