Biology subjects

Maxwell, S.

Publications and source records attributed to Maxwell, S..

7 recordsLinked to original sources

bioRxiv2025

Development of long-term oyster tissue cultures reveals cellular plasticity, regenerative potential, and sustained physiological activity

Molluscs are ecologically and economically significant, yet progress in understanding their cellular biology has been constrained by the lack of reliable molluscan cell culture systems. Insights into key molluscan biology such as immunity, biomineralization, and host-pathogen interactions, has previously been limited by short term survival of primary culture systems. Here, we establish reproducible long-term in vitro and ex vivo cultures of cells and tissues from the oyster, Ostrea edulis, including whole heart, visceral mass, mantle, and gill explants. Explanted tissues remained viable for over two months, with whole hearts maintaining rhythmic, stimulus-responsive contractions for up to nine months. Cultures maintained structural and functional features while uncovering cellular plasticity, including haemocyte granule turnover, auricular epithelial remodelling with novel ciliation, and the emergence of de novo multicellular microtissues. Previously under-characterized tissue-specific cell types were maintained in culture, including adipocytes from the visceral mass and myocytes from the mantle, thereby expanding the cellular repertoire accessible in vitro. Mineralized structures were observed across tissue cultures, highlighting the potential of this system for studying biomineralization. By sustaining diverse cell types in vitro, these cultures provide a novel tractable platform for studying molluscan diseases, while also laying the foundation for deeper investigation into comparative invertebrate biology and the development of immortalised molluscan cell lines.

cell biology↗

bioRxiv2025

Lymph-node transcriptomics define prognostic immune states in mucosal melanoma and reveal IBA1 as a practical biomarker for improved prognosis

Mucosal melanoma (MM) is a rare and aggressive cancer in humans with poor prognosis and limited response to immunotherapy or targeted therapy. Progress has been hindered by the lack of immune-competent, translational models. Dogs develop oral mucosal melanoma (OMM), a biologically equivalent disease, making them a valuable companion animal model that shares the human environment and immune context. In this study, we present the first transcriptomic analysis of regional lymph nodes in dogs with OMM, revealing that lymph nodes stratify into two distinct subgroups, independent of histopathological metastatic status at time of surgery, and which can be succinctly captured with a 35-gene signature. Notably, this stratification correlates with survival outcomes, providing unique early prognostic insights at the time of diagnosis. Furthermore, we explore the immune landscape of these subgroups and identify IBA1+ monocyte/macrophage infiltration as a key distinguishing biomarker. Using immunohistochemistry (IHC) and digital pathology, we demonstrate that higher IBA1 expression is associated with the transcriptomic subgroups associated with improved survival. These findings highlight IBA1 as a potential biomarker for risk stratification, offering a clinically relevant tool for refining prognosis and guiding treatment decisions in canine OMM. HighlightsO_LITranscriptomic profiling of canine OMM lymph nodes identifies two prognostic subgroups, independent of histopathological metastatic status. C_LIO_LILymph node transcriptomic stratification correlates with survival, providing prognostic insights beyond conventional histopathology at the time of diagnosis. C_LIO_LIIBA1+ monocyte/macrophage infiltration is associated with improved survival, and shows strong diagnostic potential via immunohistochemistry, supporting its use as a clinically feasible stratification tool. C_LI

cancer biology↗

bioRxiv2024

Structures of the human adult muscle-type nicotinic receptor in resting and desensitised states

Muscle-type nicotinic acetylcholine receptor (AChR) is the key signalling molecule in neuromuscular junctions. Here we present the structures of full-length human adult receptors in complex with Fab35 in -bungarotoxin (BuTx)-bound resting states, and in acetylcholine (ACh)-bound desensitised states. In addition to identifying the conformational changes during recovery from desensitisation, we also used electrophysiology to probe the effects of eight previously unstudied AChR genetic variants found in congenital myasthenic syndrome (CMS) patients, revealing they cause either slow- or fast-channel CMS characterised by prolonged or abbreviated ion channel bursts. The combined kinetic and structural data offer a better understanding of both AChR state transition and the pathogenic mechanisms of disease variants.

neuroscience↗

bioRxiv2024

Identification of SLC45A4 as a pain gene encoding a neuronal polyamine transporter.

Polyamines are regulatory metabolites with key roles in transcription, translation, cell signalling and autophagy1. They are implicated in multiple neurological disorders including stroke, epilepsy and neurodegeneration and can regulate neuronal excitability through interactions with ion channels2. Polyamines have been linked to pain showing altered levels in human persistent pain states and modulation of pain behaviour in animal models3. However, the systems governing polyamine transport within the nervous system remain unclear. In undertaking a Genome Wide Association Study (GWAS) of chronic pain intensity in the UK-Biobank we found significant association with variants mapping to the SLC45A4 gene locus. In the mouse nervous system SLC45A4 expression is enriched in all sensory neuron sub-types within the dorsal root ganglion including nociceptors. Cell-based assays show that SLC45A4 is a selective plasma membrane polyamine transporter, whilst the cryo-EM structure reveals a novel regulatory domain and basis for polyamine recognition. Mice lacking SLC45A4 show normal mechanosensitivity but reduced sensitivity to noxious heat and algogen induced tonic pain that is associated with reduced excitability of peptidergic nociceptors. Our findings thus establish a role for neuronal polyamine transport in pain perception and identify a new target for therapeutic intervention in pain treatment.

neuroscience↗

bioRxiv2021

Developmental and behavioral phenotypes in a new mouse model of DDX3X syndrome

BackgroundMutations in the X-linked gene DDX3X account for ~2% of intellectual disability in females, often co-morbid with behavioral problems, motor deficits, and brain malformations. DDX3X encodes an RNA helicase with emerging functions in corticogenesis and synaptogenesis. MethodsWe generated a Ddx3x haploinsufficient mouse (Ddx3x+/-) with construct validity for DDX3X loss-of-function mutations. We used standardized batteries to assess developmental milestones and adult behaviors, as well as magnetic resonance imaging and immunostaining of cortical projection neurons to capture early postnatal changes in brain development. ResultsDdx3x+/- mice show physical, sensory, and motor delays that evolve into behavioral anomalies in adulthood, including hyperactivity, anxiety-like behaviors, cognitive impairments, and motor deficits. Motor function further declines with age. These behavioral changes are associated with a reduction in brain volume, with some regions (e.g., cortex and amygdala) disproportionally affected. Cortical thinning is accompanied by defective cortical lamination, indicating that Ddx3x regulates the balance of glutamatergic neurons in the developing cortex. ConclusionsThese data shed new light on the developmental mechanisms driving DDX3X syndrome and support face validity of this novel pre-clinical mouse model.

neuroscience↗

bioRxiv2020

Structural correlates of human muscle nicotinic acetylcholine receptor subunit assembly mediated by δ(+) interface residues

Muscle nicotinic acetylcholine receptors are a class of heteropentameric ligand-gated cation channels with constituent subunits adopting a fixed stoichiometric arrangement. The specific amino acid residues that govern subunit ordering are however, only partially understood. By integrating all-atom molecular dynamics simulations, bioinformatics, two-electrode voltage clamp electrophysiology and 125I--bungarotoxin assays of chimeric nAChR subunits, we identify residues across the extracellular, transmembrane and extended M4 helix of the {delta} subunit that make structural signatures that contribute to intransigent assembly rules. Furthermore, functional differences observed in 2{delta}2{beta} receptors can be rationalized by changes in dynamical behavior that manifest themselves at the agonist binding site.

neuroscience↗

bioRxiv2018

CoPhosK: A Method for Comprehensive Kinase Substrate Annotation Using Co-phosphorylation Analysis

We present CoPhosK to predict kinase-substrate associations for phosphopeptide substrates detected by mass spectrometry (MS). The tool utilizes a Naive Bayes framework with priors of known kinase-substrate associations (KSAs) to generate its predictions. Through the mining of MS data for the collective dynamic signatures of the kinases substrates revealed by correlation analysis of phosphopeptide intensity data, the tool infers KSAs in the data for the considerable body of substrates lacking such annotations. We benchmarked the tool against existing approaches for predicting KSAs that rely on static information (e.g. sequences, structures and interactions) using publically available MS data, including breast, colon, and ovarian cancer models. The benchmarking reveals that co-phosphorylation analysis can significantly improve prediction performance when static information is available (about 35% of sites) while providing reliable predictions for the remainder, thus tripling the KSAs available from the experimental MS data providing a to comprehensive and reliable characterization of the landscape of kinase-substrate interactions well beyond current limitations. Author SummaryKinases play an important role in cellular regulation and have emerged as an important class of drug targets for many diseases, particularly cancers. Comprehensive identification of the links between kinases and their substrates enhances our ability to understand the underlying mechanism of diseases and signalling networks to drive drug discovery. Most of the current computational methods for prediction of kinase-substrate associations use static information such as sequence motifs and physical interactions to generate predictions. However, phosphorylation is a dynamic process and these static predictions may overlook unique features of cellular context, where kinases may be rewired. In this manuscript, we propose a computational method, CoPhosK, which uses the mass spectrometry based phosphoproteomics data to predict the kinase for all identified phosphosites in the experiment. We show that our approach complements and extends existing approaches.

bioinformatics↗