Biology subjects

Davies, C.

Publications and source records attributed to Davies, C..

30 records · Page 2Linked to original sources

bioRxiv2022

Campylobacter jejuni modulates reactive oxygen species production and NADPH oxidase 1 expression in human intestinal epithelial cells

Campylobacter jejuni is the major bacterial cause of foodborne gastroenteritis worldwide. Mechanistically, how this pathogen interacts with intrinsic defence machinery of human intestinal epithelial cells (IECs) remains elusive. To address this, we investigated how C. jejuni counteracts the intracellular and extracellular reactive oxygen species (ROS) in IECs. Our work shows that C. jejuni differentially regulates intracellular and extracellular ROS production in human T84 and Caco-2 cells. C. jejuni downregulates the transcription and translation of Nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase (Nox1), a key ROS-generating enzyme in IECs and antioxidant defence genes cat and sod1. Furthermore, inhibition of Nox1 by diphenylene iodonium (DPI) and siRNA reduced C. jejuni ability to interact, invade and intracellularly survive within T84 and Caco-2 cells. Collectively, these findings provide mechanistic insight into how C. jejuni modulates the IEC defence machinery.

microbiology↗

bioRxiv2021

Aberrant paracrine signalling for bone remodelling underlies the mutant histone-driven giant cell tumour of bone.

Oncohistones represent compelling evidence for a causative role of epigenetic perturbations in cancer. Giant cell tumours of bone (GCTs) are characterised by a mutated histone H3.3 as the sole genetic driver present in bone-forming osteoprogenitor cells but absent from abnormally large bone-resorbing osteoclasts which represent the hallmark of these neoplasms. While these striking features imply a pathogenic interaction between mesenchymal and myelomonocytic lineages during GCT development, the underlying mechanisms remain unknown. We show that the changes in the transcriptome and epigenome in the mesenchymal cells caused by the H3.3-G34W mutation contribute to increase osteoclast recruitment in part via reduced expression of the TGF{beta}-like soluble factor, SCUBE3. In turn, osteoclasts secrete unregulated amounts of SEMA4D enhancing proliferation of mutated osteoprogenitors and arresting their maturation. These findings provide a mechanism by which GCTs undergo differentiation upon denosumab treatment, a drug that depletes osteoclasts. In contrast, gain of hTERT activity, commonly found in malignant GCT, makes neoplastic cells insensitive to osteoclasts, predicting the unresponsiveness to denosumab. We provide a mechanism for GCT initiation and its response to current treatment, the basis of which is dysfunctional cross-talk between bone-forming and bone-resorbing cells, emphasising the importance of tumor/microenvironment bidirectional interactions in tumorigenesis.

cancer biology↗

bioRxiv2021

Reducing voltage-dependent potassium channel Kv3.4 levels ameliorates synapse loss in a mouse model of Alzheimers disease

Synapse loss is associated with cognitive decline in Alzheimers disease (AD) and owing to their plastic nature, synapses are an ideal target for therapeutic intervention. Oligomeric amyloid beta (A{beta}) around amyloid plaques is known to contribute to synapse loss in mouse models and is associated with synapse loss in human AD brain tissue, but the mechanisms leading from A{beta} to synapse loss remain unclear. Recent data suggest that the fast-activating and -inactivating voltagegated potassium channel subtype 3.4 (Kv3.4) may play a role in A{beta}-mediated neurotoxicity. Here, we tested whether this channel could also be involved in A{beta} synaptotoxicity. Using adeno-associated virus and CRISPR (clustered regularly interspaced short palindromic repeats) technology, we reduced Kv3.4 expression in neurons of the somatosensory cortex of APP/PS1 mice. These mice express human familial AD associated mutations in amyloid precursor protein and presenilin 1 and develop amyloid plaques and plaque-associated synapse loss similar to that observed in AD brain. We observe that reducing Kv3.4 levels ameliorates dendritic spine loss and changes spine morphology compared to control virus. In support of translational relevance, Kv3.4 protein was observed in human AD and control brain and is associated with synapses in human iPSC-derived cortical neurons. Interestingly, we observe a decrease in Kv3.4 expression in iPSC derived cortical neurons when they are challenged with human Alzheimers disease derived brain homogenate. These results suggest that approaches to reduce Kv3.4 expression and/or function could be protective against A{beta}-induced synaptic alterations.

neuroscience↗

bioRxiv2021

Task-independent acute effects of delta-9-tetrahydrocannabinol on human brain function and its relationship with cannabinoid receptor gene expression: a neuroimaging meta-regression analysis

BackgroundThe neurobiological mechanisms underlying the effects of delta-9-tetrahydrocannabinol (THC) remain unclear. Here, we examined the spatial acute effect of THC on human on regional brain activation or blood flow (hereafter called activation signal) in a core network of brain regions that subserve a multitude of processes. We also investigated whether the neuromodulatory effects of THC are related to the local expression of its key molecular target, cannabinoid-type-1 (CB1R) but not type-2 (CB2R) receptor. MethodsA systematic search was conducted of acute THC-challenge studies using fMRI, PET, and arterial spin labelling in accordance with established guidelines. Using pooled summary data from 372 participants, tested using a within-subject repeated measures design under experimental conditions, we investigated the effects of a single dose (6-42mg) of THC, compared to placebo, on brain signal. FindingsAs predicted, THC augmented the activation signal, relative to placebo, in the anterior cingulate, superior frontal cortices, middle temporal and middle and inferior occipital gyri, striatum, amygdala, thalamus, and cerebellum crus II and attenuated it in the middle temporal gyrus (spatially distinct from the cluster with THC-induced increase in activation signal), superior temporal gyrus, angular gyrus, precuneus, cuneus, inferior parietal lobule, and the cerebellum lobule IV/V. Using post-mortem gene expression data from an independent cohort from the Allen Human Brain atlas, we found a direct relationship between the magnitude of THC-induced brain signal change, indexed using pooled effect-size estimates, and CB1R gene expression, a proxy measure of CB1R protein distribution, but not CB2R expression. A dose-response relationship was observed with THC dose in certain brain regions. InterpretationThese meta-analytic findings shed new light on the localisation of the effects of THC in the human brain, suggesting that THC has neuromodulatory effects in regions central to many cognitive tasks and processes, with greater effects in regions with higher levels of CB1R expression.

neuroscience↗

bioRxiv2021

Gestational methylazoxymethanol acetate administration alters α5GABAA and NMDA receptor density: An integrated neuroimaging, behavioral and pharmacological study

Hippocampal hyperactivity driven by GABAergic interneuron deficits and NMDA receptor hypofunction is associated with the hyperdopaminergic state often observed in schizophrenia. Furthermore, previous research in the methylazoxymethanol acetate (MAM) rat model has demonstrated that repeated peripubertal diazepam administration can prevent the emergence of adult hippocampal hyperactivity, dopamine system hyperactivity, and associated psychosis-relevant behaviors. Here, we sought to characterize hippocampal GABAA and NMDA receptors in MAM-treated rats and to elucidate the receptor mechanisms underlying the promising effects of peripubertal diazepam exposure. Quantitative receptor autoradiography was used to measure receptor density in dorsal hippocampus CA1, ventral hippocampus CA1, and in ventral subiculum. Specifically, [3H]-Ro15-4513 was used to quantify the density of 5 GABAA receptors (5GABAAR), [3H]-flumazenil to quantify 1-3;5GABAAR, and [3H]-MK801 to quantify NMDA receptors. MAM rats exhibited anxiety and schizophrenia-relevant behaviors as measured by elevated plus maze and amphetamine-induced hyperlocomotion (AIH), although diazepam only partially rescued these behaviors. 5GABAAR density was reduced in MAM-treated rats in all hippocampal sub-regions, and negatively correlated with AIH. Ventral hippocampus CA1 5GABAAR density was positively correlated with anxiety-like behavior. Dorsal hippocampus CA1 NMDA receptor density was increased in MAM-treated rats, and positively correlated with AIH. [3H]-Flumazenil revealed no significant effects. Finally, we found no significant effect of diazepam treatment on receptor densities, potentially related to the only partial rescue of schizophrenia-relevant phenotypes. Overall, our findings provide first evidence of 5GABAAR and NMDA receptor abnormalities in the MAM model, suggesting that more selective pharmacological agents may become a novel therapeutic mechanism in schizophrenia.

neuroscience↗

bioRxiv2021

Genomic analysis of patient-derived xenograft models reveals intra-tumor heterogeneity in endometrial cancer and can predict tumor growth inhibition with talazoparib

BackgroundEndometrial cancer (EC) is a major gynecological cancer with increasing incidence. It comprised of four molecular subtypes with differing etiology, prognoses, and response to chemotherapy. In the future, clinical trials testing new single agents or combination therapies will be targeted to the molecular subtype most likely to respond. Pre-clinical models that faithfully represent the molecular subtypes of EC are urgently needed, we sought to develop and characterize a panel of novel EC patient-derived xenograft (PDX) models. MethodsHere, we report whole exome or whole genome sequencing of 11 PDX models and the matched primary tumor. Analysis of multiple PDX lineages and passages was performed to study tumor heterogeneity across lineages and/or passages. Based on recent reports of frequent defects in the homologous recombination (HR) pathway in EC, we assessed mutational signatures and HR deficiency scores and correlated these with in vivo responses to the PARP inhibitor (PARPi) talazoparib in six PDXs representing the different molecular subtypes of EC. ResultsPDX models were successfully generated from all four molecular subtypes of EC and uterine carcinosarcomas, and they recapitulated morphology and the molecular landscape of primary tumors without major genomic drift. We also observed a wide range of inter-tumor and intra-tumor heterogeneity, well captured by different PDX lineages, which could lead to different treatment responses. An in vivo response to talazoparib was detected in two p53mut models consistent with stable disease, however both lacked the HR deficiency genomic signature. ConclusionsEC PDX models represent the four molecular subtypes of disease and can capture intra-tumoral heterogeneity of the original primary tumor. PDXs of the p53mut molecular subtype showed sensitivity to PARPi, however, deeper and more durable responses will likely require combination of PARPi with other agents.

genomics↗

bioRxiv2021

TMEM97 increases in synapses and is a potential synaptic Aβ binding partner in human Alzheimer's disease

Synapse loss correlates with cognitive decline in Alzheimers disease, and soluble oligomeric amyloid beta is implicated in synaptic dysfunction and loss. An important knowledge gap is the lack of understanding of how amyloid beta leads to synapse degeneration. In particular, there has been difficulty in determining whether there is a synaptic receptor that binds amyloid beta and mediates toxicity. While many candidates have been observed in model systems, their relevance to human AD brain remains unknown. This is in part due to methodological limitations preventing visualization of amyloid beta binding at individual synapses. To overcome this limitation, we combined two high resolution microscopy techniques: array tomography and Forster resonance energy transfer (FRET) to image over 1 million individual synaptic terminals in temporal cortex from AD (n=9) and age matched control cases (n=6). Within postsynaptic densities, amyloid beta generates a FRET signal with transmembrane protein 97, cellular prion protein, and postsynaptic density 95. Transmembrane protein 97 is also present in a higher proportion of postsynapses in Alzheimers brain compared to controls. Further, we inhibited amyloid beta / transmembrane protein 97 interaction in a mouse model of amyloidopathy by treating with the an allosteric modulator CT1812 or vehicle. CT1812 drug concentration correlated negatively with synaptic FRET signal between transmembrane protein 97 and amyloid beta. In human induced pluripotent stem cell derived neurons challenged with human Alzheimers brain homogenate, transmembrane protein 97 and amyloid beta are present in synapses. Transcriptional changes are induced by A{beta} including changes in genes involved in neurodegeneration and neuroinflammation. CT1812 treatment of these neurons caused changes in gene sets involved in synaptic function. These data support a role for transmembrane protein 97 in the synaptic binding of amyloid beta in human Alzheimers disease brain where it may mediate synaptotoxicity.

neuroscience↗

bioRxiv2020

VGLL1-directed TEAD activation drives endocrine therapy resistance in estrogen receptor positive breast cancer

Resistance to endocrine therapies (ET) is common in estrogen receptor (ER) positive breast cancer and most relapsed patients die with ET-resistant disease. While genetic mutations provide explanations for some relapsed patients1, mechanisms of resistance remain undefined in many cases. Drug-induced epigenetic reprogramming provides possible routes to resistance2. By analysing histone H3 lysine 27 acetylation (H3K27ac) profiles in models of ET resistance, we discovered that selective ER down-regulators (SERDs) such as fulvestrant promote epigenetic activation of VGLL1, a co-activator for TEAD transcription factors. We show that VGLL1, acting via TEADs, promotes expression of genes that drive growth of fulvestrant-resistant breast cancer cells. Pharmacological disruption of VGLL1/TEAD4 interaction inhibits VGLL1/TEAD transcriptional programmes to block growth of the resistant cells and prevents growth. Among the VGLL1/TEAD-regulated genes, we identify EGFR, whereby VGLL1-directed EGFR upregulation sensitises fulvestrant-resistant breast cancer cells to EGFR inhibitors. Taken together, our findings identify VGLL1 as a transcriptional driver in ET resistance and advance new therapeutic possibilities for relapsed ER+ breast cancer patients.

cancer biology↗

bioRxiv2019

Temporal proteomic analysis of BK polyomavirus infection reveals virus-induced G2 arrest and highly effective evasion of innate immune sensing

BK polyomavirus (BKPyV) is known to cause severe morbidity in renal transplant recipients and can lead to graft rejection. The simple 5.2 kilobase pair dsDNA genome expresses just seven known proteins, thus it relies heavily on host machinery to replicate. How the host proteome changes over the course of infection is key to understanding this host:virus interplay. Here for the first time quantitative temporal viromics has been used to quantify global changes in >9,000 host proteins in two types of primary human epithelial cell throughout 72 hours of BKPyV infection. These data demonstrate the importance both of cell cycle progression and pseudo-G2 arrest in effective BKPyV replication, along with a surprising lack of innate immune response throughout the whole virus replication cycle. BKPyV thus evades pathogen recognition to prevent activation of innate immune responses in a sophisticated manner.

microbiology↗

bioRxiv2018

Reducing tau ameliorates behavioural and transcriptional deficits in a novel model of Alzheimer’s disease

SummaryOne of the key knowledge gaps blocking development of effective therapeutics for Alzheimers disease (AD) is the lack of understanding of how amyloid beta (A{beta}) and tau cooperate in causing disease phenotypes. Within a mouse tau deficient background, we probed the molecular, cellular and behavioural disruption triggered by wild-type human taus influence on human A{beta}-induced pathology. We find that A{beta} and tau work cooperatively to cause a hyperactivity phenotype and to cause downregulation of gene transcription including many involved in synaptic function. In both our mouse model and in human post-mortem tissue, we observe accumulation of pathological tau in synapses, supporting the potential importance of synaptic tau. Importantly, tau depletion in the mice, initiated after behavioural deficits emerge, was found to correct behavioural deficits, reduce synaptic tau levels, and substantially reverse transcriptional perturbations, suggesting that lowering tau levels, particularly at the synapse, may be beneficial in AD.\n\nHighlights- Expression of human familial Alzheimers associated mutant amyloid precursor protein and presenillin 1 with wild-type human tau in the absence of endogenous tau in a novel MAPT-AD mouse model results in behavioural deficits and downregulation of genes involved in synaptic function.\n- Tau is present in pre and postsynaptic terminals in MAPT-AD mice and human AD brain. In mice, lowering synaptic tau levels was associated with improved cognition and recovered gene expression.\n- These data suggest that A{beta} and tau act cooperatively in impairing synaptic function and that lowering tau at synapses could be a beneficial therapeutic approach in AD.

neuroscience↗

bioRxiv2018

SREBP1 drives KRT80-dependent cytoskeletal changes and invasive behavior in endocrine resistant ERα breast cancer

Approximately 30% of women diagnosed with ER breast cancer relapse with metastatic disease following adjuvant treatment with endocrine therapies1,2. The connection between acquisition of drug resistance and invasive potential is poorly understood. In this study, we demonstrate that the type II keratin topological associating domain (TAD)3 undergoes epigenetic reprogramming in cells that develop resistance to aromatase inhibitors (AI), leading to keratin 80 (KRT80) upregulation. In agreement, an increased number of KRT80-positive cells are observed at relapse in vivo while KRT80 expression associates with poor outcome using several clinical endpoints. KRT80 expression is driven by de novo enhancer activation by sterol regulatory element-binding protein 14 (SREBP1). KRT80 upregulation directly promotes cytoskeletal rearrangements at the leading edge, increased focal adhesion maturation and cellular stiffening, which collectively promote cancer cell invasion. Shear-wave elasticity imaging of prospective patients shows that KRT80 levels correlate with stiffer tumors in vivo. Collectively, our data uncover an unpredicted and potentially targetable direct link between epigenetic and cytoskeletal reprogramming promoting cell invasion in response to chronic AI treatment.

cancer biology↗

bioRxiv2018

Cross-fostering in rodents causes region-specific alterations in entorhinal cortical gamma rhythms associated with NMDA receptor dysfunction

There has recently been a large increase in the number of children placed in foster care in the United States and Europe. While this is the least worst scenario for those with a lack of appropriate biological care, it is recognised that these children are exposed to major stressors correlated with behavioural changes, particularly in the realm of social cognition into adulthood. Here we model foster care in rodents: rat pups are removed from their biological mother and placed with a non-genetically related dam. This prevented the entorhinal cortex from generating patterns of gamma rhythms required for normal parahippocampal function relevant to social interaction. These changes correlated with a reduction in NMDA receptor-mediated excitation, and changes in parvalbumin expression in interneurons. These data suggest that early life care delivered by a non-biological parent may disrupt social behaviour but, in contrast, generate neurobiological changes antagonistic to those currently associated with psychosis.\n\nSignificance StatementCross fostering is an effective approach for delineating the effect of environment from genetic influences upon behavior. This involves removal of pups from one mother and transfer to another lactating dam. This manipulation is considered as a mild form of early life stress, producing neurobehavioral changes such as alterations in social interaction. We demonstrate that cross fostering produces changes in the ability of cortical microcircuits to generate oscillatory rhythms, in particular the gamma rhythm, in brain regions important for social cognition. This reduction in gamma rhythmogenesis is related to a reduction in synaptic drive provided by the NMDA receptor. One implication of this work is that the modulation of NMDA receptors offers a potential therapeutic strategy for disorders involving impaired sociability.

neuroscience↗