Biology subjects

Farmer, M.

Publications and source records attributed to Farmer, M..

7 recordsLinked to original sources

bioRxiv2025

Intracellular Trafficking SNARE Protein, Syntaxin-6, is a Modifier of Prion and Tau Pathogenesis in vivo and in Cellular Models

Syntaxin-6, a SNARE protein involved in intracellular protein trafficking, is a proposed risk factor for sporadic prion disease, progressive supranuclear palsy and Alzheimers disease. However, no study has validated its functional role in these diseases, explored the disease stage at which it is acting nor its mechanism of action. Here, we show that syntaxin-6 acts at early stages of prion disease in experimental mice by increasing disease transmission risk following inoculation with low prion doses. Conversely, syntaxin-6 does not affect prion propagation kinetics or toxicity during established disease. Syntaxin-6 manipulation in cellular models profoundly alters the subcellular distribution and morphologies of disease-related PrP and modifies prion export. Furthermore, syntaxin-6 knockout in a transgenic tauopathy mouse model exerts protective effects on numerous physiological, behavioural and neuropathological outcome measures. Therefore, our studies firmly establish syntaxin-6 as a modifier of prion and tau pathogenesis, providing key insights into a fundamental mechanism of neurodegeneration.

neuroscience↗

bioRxiv2024

Gut Microbial Impact on Colitis and Colitis-Associated Carcinogenesis in a Primary Sclerosing Cholangitis-IBD Model

Background and AimsPrimary sclerosing cholangitis (PSC) associated inflammatory bowel diseases (IBD) increase colorectal dysplasia and malignancy risk. Current mouse models do not adequately replicate human PSC-IBD, limiting mechanistic understanding and therapeutic development. This study uses Mdr2/Il10 double knockout (DKO) mice to examine microbiota roles in mediating colitis, colitis-associated colorectal dysplasia and hepatobiliary inflammation/fibrosis. GoalDevelop and phenotype a chronic spontaneous PSC-IBD mouse model, emphasizing colitis, colonic dysplasia, hepatobiliary inflammation/ fibrosis and the functional roles of resident microbiota. MethodsWe utilized germ-free (GF) and specific-pathogen-free Mdr2/Il10 DKO, Il10-/- and Mdr2-/- mice to model PSC-IBD. We monitored colonic dysplasia progression, colitis kinetics and severity by lipocalin-2, cytokine measurement, and tissue evaluations of colon and liver. We manipulated the microbiome to assess its functional effects. ResultsDKO mice exhibited age- and region-specific accelerated colitis and spontaneous colonic dysplasia progressing to high-grade invasive adenocarcinomas. Despite aggressive colonic inflammation, DKO mice showed reduced hepatic fibrosis, increased hepatic reparative macrophages, and matrix metalloproteinase activity compared to Mdr2-/- mice. GF DKO had heightened liver inflammation and mortality with absent colitis and colonic dysplasia, reversed with microbial reconstitution from DKO mice. Changes in DKO primary/secondary bile acid profiles mirrored those in PSC-IBD. ConclusionThe Mdr2/Il10 DKO model mirrors key factors in PSC-IBD patients in terms of inflammation and carcinogenesis. We found an important role for the dysbiotic microbiota in DKO mice for disease onset and progression. Targeting microbiota and bile acid metabolism may provide promising strategies for developing effective PSC-IBD therapies.

microbiology↗

bioRxiv2024

Nitrous oxide production, mechanisms, and modeling from a denitrifying phosphorus removal bioreactor

Nitrous oxide (N2O) is a potent greenhouse gas produced as an unintentional, undesired byproduct in many nitrogen removal bioprocesses. Given the considerable challenges in managing N2O emissions from wastewater treatment, N2O could be reframed as a value-added product if intentionally generated and captured. This study assesses N2O production and mechanisms in a Coupled Aerobic-anoxic Nitrous Decomposition Operation with Phosphorus removal (CANDO+P) reactor. Optimal performance was achieved when the reactor was fed with a mixture of propionate and glucose, resulting in N2O was production up to 50% of influent nitrogen. Through 16S rRNA amplicon and shotgun metagenomic sequencing, we found that Candidatus Accumulibacter were the dominant phosphorus accumulating organism (PAO). Assembly of a high-quality metagenome-assembled genome showed that Ca. Accumulibacter encoded a full complete denitrification pathway from nitrite to nitrogen gas. We also found abundant populations of denitrifying glycogen accumulating organisms (GAO) and ordinary heterotrophic organisms (OHO). We also incorporated truncated denitrification pathways into a process model to predict N2O generation. N2O predictions were the most similar to observed results when the denitrification pathways of PAO, GAO, and OHO model populations reflected denitrification gene abundances from the metagenomic sequencing analysis. Our work demonstrates the feasibility of using non-VFA carbon for intentional N2O generation and provides broader insights into N2O generation and truncated denitrification pathways of denitrifying PAO and GAO.

microbiology↗

bioRxiv2024

Induction and characterisation of Abeta and tau pathology in AppNL-F/NL-F mice following inoculation with Alzheimer's disease brain homogenate

Alzheimers disease (AD) is defined by the accumulation of neurofibrillary tangles containing hyperphosphorylated Tau and plaques containing Amyloid-{beta} (A{beta}). The aggregation of these two proteins is considered central to the disease. The lack of animal models that can recapitulate A{beta} and tau pathologies without overexpressing these proteins has hindered AD research. Accelerating pathology by inoculating A{beta} and tau seeds has helped to understand their prion-like propagation in the brain. Previous studies failed to characterise both A{beta} and tau pathologies in vivo upon inoculating AD brain homogenates. Here we present a longitudinal and systematic study; we inoculated the AppNL-F/NL-F knockin mice, which express humanised A{beta} and murine wild-type tau, with extracts from diseased human brains to analyse the contribution of A{beta} and tau assemblies to AD pathogenesis. We found that mice inoculated with AD brain extracts evinced early and prominent amyloid deposition, while those injected with control brain extracts or vehicle did not. Parenchymal and vascular amyloid accumulated in the same brain regions affected in control-inoculated AppNL-F/NL-F mice. However, the extent of vascular amyloid far exceeded that seen in AppNL-F/NL-Fmice injected with control brain extracts, and parenchymal deposits extended to a previously untargeted brain region - the cerebellum. An end-point titration of an AD brain homogenate in AppNL-F/NL-F mice demonstrated that human A{beta} seeds can be titrated in a prion-like fashion, which is useful for sample comparison, diagnostic and risk studies. Notably, the inoculation of AppNL-F/NL-F mice with AD brain homogenate induced intense tau phosphorylation, and provides more detailed context for the inoculation of AppNL-F/NL-F mice with human samples to study temporal and mechanistic relationships between A{beta} and tau pathology, vascular amyloid deposition and bioactivity of A{beta} seeds.

neuroscience↗

bioRxiv2023

Meta-omic profiling reveals ubiquity of genes encoding for the high value nitrogen rich biopolymer cyanophycin in activated sludge microbiomes

Recovering nitrogen (N) from municipal wastewater is a promising approach to prevent nutrient pollution, reduce energy use, and transition towards a circular N bioeconomy, but remains a technologically challenging endeavor. Existing N recovery techniques are optimized for high-strength, low-volume wastewater. Therefore, developing methods to concentrate dilute N from mainstream wastewater will bridge the gap between existing technologies and practical implementation. The N-rich biopolymer cyanophycin is a promising candidate for N bioconcentration and recovery due to its solubility characteristics and potential for high levels of accumulation in a limited number of bacterial isolates. However, the cyanophycin synthesis pathway is poorly explored in natural and engineered microbiomes. In this study, we analyzed over 3700 publicly available metagenome assembled genomes (MAGs) and found that the cyanophycin synthesis gene cphA was ubiquitous across common activated sludge bacteria. Surprisingly, we found that cphA was present in all analyzed genomes of the common phosphorus accumulating organisms (PAO) Ca. Accumulibacter and Tetrasphaera, suggesting potential for simultaneous N and P bioconcentration in the same organisms. Using metatranscriptomic data, we also confirmed the expression of cphA in lab-scale bioreactors enriched with PAO. Our findings suggest that cyanophycin synthesis is a ubiquitous metabolic pathway in activated sludge microbiomes and therefore may have potential for integration in existing biological nutrient removal and recovery processes. We anticipate this work to be a starting point for future evaluations of combined N and P bioaccumulation, with the ultimate goal of advancing widespread adoption of nutrient recovery from municipal wastewater.

ecology↗

bioRxiv2022

Impact of cellular prion protein expression on disease progression and pathology in two mouse models of Alzheimer's disease

The aggregation of amyloid-{beta} (A{beta}) monomers increases their neurotoxicity, and these oligomeric species are thought to be central to the pathogenesis of Alzheimers disease. Unsurprisingly for such a complex disease, current Alzheimers disease mouse models fail to fully mimic the clinical disease in humans. Moreover, results obtained in a given mouse model are not always reproducible in a different model. Cellular prion protein (PrPC) is now an established receptor for A{beta} oligomers. However, different groups studying the A{beta}-PrPC interaction in vivo using a variety of mouse models have obtained contradictory results. Here we performed a longitudinal study in two commonly used AD mouse models using a range of biochemical, histological and behavioural techniques and found similar contradictory results and a possible explanation for the discrepancy. We propose that these two mouse models produce A{beta} oligomers with different conformations. Therefore, binding to PrPC and the subsequent activation of toxic signalling cascade will occur only when the A{beta} oligomer species with appropriate conformation are present. Hence, it is crucial to select the appropriate model producing the appropriate species of A{beta} oligomers to study specific aspects of {beta}-amyloidosis and its downstream pathways. Further conformational characterisation of A{beta} oligomers and their binding to PrPC is required to better understand A{beta} neurotoxicity.

neuroscience↗

bioRxiv2021

Protective and aggressive bacterial subsets and metabolites modify hepatobiliary inflammation and fibrosis in PSC.

ObjectiveConflicting microbiota data exist for primary sclerosing cholangitis (PSC) and experimental models. Goal: Define complex interactions between resident microbes and their association in PSC patients by studying antibiotic-treated specific pathogen-free (SPF) and germ-free (GF) multi-drug-resistant 2 deficient (mdr2-/-) mice. DesignWe measured weights, liver enzymes, RNA expression, histological, immunohistochemical and fibrotic biochemical parameters, fecal 16s rRNA gene profiling, and metabolomic endpoints in gnotobiotic and antibiotic-treated SPF mdr2-/- mice and targeted metagenomic analysis in PSC patients. ResultsGF mdr2-/- mice had exaggerated hepatic inflammation and fibrosis with 100% mortality by 8 weeks; early SPF autologous stool transplantation rescued liver-related mortality. Broad-spectrum antibiotics and vancomycin alone accelerated disease in weanling SPF mdr2-/- mice, indicating that vancomycin-sensitive resident microbiota protect against hepatobiliary disease. Vancomycin treatment selectively decreased Lachnospiraceae and short-chain fatty acids (SCFAs) but expanded Enterococcus and Enterobacteriaceae. Antibiotics increased cytolysin-expressing E. faecalis and E. coli liver translocation; colonization of gnotobiotic mdr2-/- mice with translocated E. faecalis and E. coli strains accelerated liver inflammation and mortality. Lachnospiraceae colonization of antibiotic pre-treated mdr2-/- mice reduced liver fibrosis, inflammation and translocation of pathobionts, while Lachnospiraceae-produced SCFA decreased fibrosis. Fecal E. faecalis/ Enterobacteriaceae was positively and Lachnospiraceae was negatively associated with PSC patients clinical severity Mayo risk scores. ConclusionsWe identified specific functionally protective and detrimental resident bacterial species in mdr2-/- mice and PSC patients with associated clinical outcomes. These insights may guide personalized targeted therapeutic interventions in PSC patients.

microbiology↗