Biology subjects

Fowler, S.

Publications and source records attributed to Fowler, S..

7 recordsLinked to original sources

bioRxiv2025

Microbiota Modulation Induces Elevated Duodenal Eosinophils Upon Gluten Exposure in Mice: Implications for Non-Coeliac Gluten Sensitivity

A growing proportion of the non-celiac population experience adverse symptoms to gluten. The pathogenesis of non-coeliac gluten sensitivity (NCGS) is unclear, but elevated duodenal eosinophils and altered mucosa-associated microbiota (MAM) populations have been reported. Given the microbiomes role in gluten digestion and its susceptibility to antibiotics, we hypothesised that altering the microbiome with antibiotics would modify immune responses to gluten in mice. BALB/C mice consuming gluten-free chow received amoxicillin/clavulanate (5mg/kg) or PBS-vehicle daily for 5 days. Mice were then treated with a 3mg wheat-gluten suspension, or vehicle, on days 4 and 5 before sacrifice on day 7. Duodenal immune cells were analysed by histology and flow cytometry, while the duodenal MAM and faecal microbiome were characterised via 16S rRNA and shotgun metagenomic sequencing, respectively. Antibiotic treatment followed by gluten reintroduction significantly reduced Staphylococcus in the duodenal MAM, enriched Bacteroides in faeces, and resulted in altered microbial carbohydrate and lipid metabolism, compared to vehicle controls. Treatment with antibiotics and gluten also increased duodenal eosinophils which positively correlated with the genus Blautia. Flow cytometry revealed that antibiotics and gluten treatment resulted in a greater proportion of active eosinophils and epithelial {gamma}{delta} T-cells, compared to vehicle control mice. This study demonstrated that modulating the microbiome with antibiotics was sufficient to alter the immune response to gluten in mice. These findings suggest that the microbiome may determine the capacity for gluten to induce an immune response and offers a valuable insight into potential mechanisms underlying NCGS. New & NoteworthyA mouse model examined how microbial modulation affects immune responses to gluten. Antibiotic treatment followed by gluten reintroduction reduced duodenal Staphylococcus and altered microbial carbohydrate and lipid metabolism pathways in the faecal microbiome. Antibiotics and gluten treatment resulted in increased abundance and activation of duodenal eosinophils, and elevated {gamma}{delta} T-cells in the duodenal epithelium. These findings highlight the role the microbiome plays in gluten-induced immune responses, providing insights into mechanisms behind non-coeliac gluten sensitivity.

immunology↗

bioRxiv2025

Hidden Diversity of Threatened Sharks and Rays in the Global Meat Trade

International wildlife trade is a major source of biodiversity loss, yet many species lie hidden within aggregated data that conceals trade impacts. We overcome this problem for the largest vertebrate wildlife trade globally - shark and ray meat - comprising 438 538 mt yr-1 across more than 150 species, 76% of which are Threatened. Revealed trade contains greater quantities of skates (+10%), hammerheads (+8%), and smoothhounds, dogfishes & tope (+5%), and fewer pelagic sharks (-38%) than previously known. Shorttail yellownose skate, smoothound, silky, mako, and blue sharks are the most underreported meat species, due to aggregated landings from China, Argentina, Japan, and Indonesia, demonstrating international trade in shark and ray meat as a diverse, pervasive, and previously hidden source of fishing mortality for many threatened species.

ecology↗

bioRxiv2025

Fexinidazole and Corallopyronin A target Wolbachia-infected sheath cells present in filarial nematodes

The discovery of the endosymbiotic bacteria Wolbachia as an obligate symbiont of filarial nematodes has led to antibiotic-based treatments for filarial diseases. While lab and clinical studies have yielded promising results, recent animal studies reveal that Wolbachia levels may rebound following treatment with suboptimal doses of the antibiotic rifampicin. Previous work showed that a likely source of the bacterial rebound in females were dense clusters of Wolbachia in ovarian tissue. The number, size, and density of these Wolbachia clusters were not diminished despite antibiotic treatment. Here we define the cellular characteristics of the Wolbachia clusters in Brugia pahangi (wBp) and identify drugs that also target them. We have evidence that the Wolbachia clusters originate from newly formed sheath cells adjacent to the ovarian Distal Tip Cells. The dramatically enlarged volume of an infected sheath cell is strikingly similar to endosymbiont-induced bacteriocytes found in many insect species. Ultrastructural analysis reveals that the clustered Wolbachia present within the sheath cells exhibit a distinct morphology and form direct connections with the oocyte membrane and possibly the cytoplasm. This includes membrane-based channels providing a connection between Wolbachia-infected sheath cells and oocytes. We also determined that the Wolbachia within the sheath cells are either quiescent or replicating at a very low rate. Screens of known antibiotics and other drugs revealed that two drugs, Fexinidazole and Corallopyronin A, significantly reduced the number of clustered Wolbachia located within the sheath cells.

pathology↗

bioRxiv2022

Distinct Wolbachia localization patterns in oocytes of diverse host species reveal multiple strategies of maternal transmission

A broad array of endosymbionts radiate through host populations via vertical transmission, yet much remains unknown concerning the cellular basis, diversity and routes underlying this transmission strategy. Here we address these issues, by examining the cellular distributions of Wolbachia strains that diverged up to 50 million years ago in the oocytes of 18 divergent Drosophila species. This analysis revealed three Wolbachia distribution patterns: 1) a tight clustering at the posterior pole plasm (the site of germline formation); 2) a concentration at the posterior pole plasm, but with a significant bacteria population distributed throughout the oocyte; 3) and a distribution throughout the oocyte, with none or very few located at the posterior pole plasm. Examination of this latter class indicates Wolbachia accesses the posterior pole plasm during the interval between late oogenesis and the blastoderm formation. We also find that one Wolbachia strain in this class concentrates in the posterior somatic follicle cells that encompass the pole plasm of the developing oocyte. In contrast, strains in which Wolbachia concentrate at the posterior pole plasm generally exhibit no or few Wolbachia in the follicle cells associated with the pole plasm. Taken together, these studies suggest that for some Drosophila species, Wolbachia invade the germline from neighboring somatic follicle cells. Phylogenomic analysis indicates that closely related Wolbachia strains tend to exhibit similar patterns of posterior localization, suggesting that specific localization strategies are a function of Wolbachia-associated factors. Previous studies revealed that endosymbionts rely on one of two distinct routes of vertical transmission: continuous maintenance in the germline (germline-to-germline) or a more circuitous route via the soma (germline-to-soma-to-germline). Here we provide compelling evidence that Wolbachia strains infecting Drosophila species maintain the diverse arrays of cellular mechanisms necessary for both of these distinct transmission routes. This characteristic may account for its ability to infect and spread globally through a vast range of host insect species.

cell biology↗

bioRxiv2022

Genome-Wide Association Study Finds Multiple Loci Associated with Intraocular Pressure in HS Rats

Elevated intraocular pressure (IOP) is influenced by environmental and genetic factors. Increased IOP is a major risk factor for most types of glaucoma, including primary open angle glaucoma (POAG). Investigating the genetic basis of IOP may lead to a better understanding of the molecular mechanisms of POAG. The goal of this study was to identify genetic loci involved in regulating IOP using outbred heterogeneous stock (HS) rats. HS rats are a multigenerational outbred population derived from eight inbred strains that have been fully sequenced. This population is ideal for genome-wide association studies (GWASs) owing to the accumulated recombinations among well-defined haplotypes, the relatively high allele frequencies, the accessibility to a large collection of tissue samples, and the large allelic effect size compared to human studies. Both male and female HS rats (N=1,812) were used in the study. Genotyping-by-sequencing was used to obtain ~3.5 million single nucleotide polymorphisms (SNP) from each individual. SNP heritability for IOP in HS rats was 0.32, which agrees with other studies. We performed a GWAS for the IOP phenotype using a linear mixed model and used permutation to determine a genome-wide significance threshold. We identified three genome-wide significant loci for IOP on chromosomes 1, 5, and 16. Next, we sequenced the mRNA of 51 whole eye samples to find cis-eQTLs to aid in identification of candidate genes. We report 5 candidate genes within those loci: Tyr, Ctsc, Plekhf2, Ndufaf6 and Angpt2. Tyr, Ndufaf6 and Angpt2 genes have been previously implicated by human GWAS of IOP-related conditions. Ctsc and Plekhf2 genes represent novel findings that may provide new insight into the molecular basis of IOP. This study highlights the efficacy of HS rats for investigating the genetics of elevated IOP and identifying potential candidate genes for future functional testing. Contribution to the field statementGlaucoma is the leading cause of irreversible blindness worldwide. Intraocular pressure (IOP) is the only known modifiable risk factor. This study describes results of the genome-wide association study (GWAS) performed in outbred rats that identifies known and novel genes involved in IOP regulation. To our knowledge, this is the first GWAS performed for IOP in a rat model. Identifying novel candidate genes in the rat model provides insight into the risk factors for glaucoma in humans and potential pharmacological targets for regulating IOP. The rat model is advantageous for studying natural variations in IOP, controlling environmental exposures, and providing easier access to tissue that can be used in phenotyping and gene expression in future studies.

genomics↗

bioRxiv2018

Unc 51-like autophagy-activating kinase (ULK1) mediates clearance of free {alpha}-globin in {beta}-thalassemia

Erythroid maturation is coordinated to maximize the production of hemoglobin A heterotetramers (2{beta}2) and minimize the accumulation of potentially toxic free - or {beta}-globin subunits. In {beta}-thalassemia, mutations in the {beta}-globin gene cause a build-up of free -globin, which forms intracellular precipitates that impair erythroid cell maturation and viability. Protein quality-control systems mitigate {beta}-thalassemia pathophysiology by degrading toxic free -globin. We show that loss of the Unc 51-like autophagy-activating kinase gene Ulk1 in {beta}-thalassemic mice reduces autophagic clearance of -globin in red cell precursors and exacerbates disease phenotypes, whereas inactivation of the canonical autophagy gene Atg5 has minimal effects. Systemic treatment with rapamycin to inhibit the ULK1 inhibitor mTORC1 reduces -globin precipitates and lessens pathologies in {beta}-thalassemic mice, but not in those lacking Ulk1. Similarly, rapamycin reduces free -globin accumulation in erythroblasts derived from {beta}-thalassemic patient CD34+ hematopoietic progenitors. Our findings identify a new, drug-regulatable pathway for ameliorating {beta}-thalassemia.\n\nOne Sentence SummaryRapamycin alleviates {beta}-thalassemia by stimulating ULK1-dependent autophagy of toxic free -globin.

cell biology↗

bioRxiv2017

LIM Protein Ajuba associates with the RPA complex through direct and cell cycle-dependent interaction with the RPA70 subunit.

DNA damage response pathways are essential for genome stability and cell survival. Specifically, the ATR kinase is activated by DNA replication stress. An early event in this activation is the recruitment and phosphorylation of RPA, a single stranded DNA binding complex composed of three subunits, RPA70,RPA32 and RPA14. We have previously shown that the LIM protein Ajuba associates with RPA, and that depletion of Ajuba leads to potent activation of ATR. In this study, we show evidence that the Ajuba-RPA interaction occurs through direct protein contact with RPA70, and that their association is cell cycle-regulated and is reduced upon DNA replication stress. We propose a model in which Ajuba negatively regulates the ATR pathway by directly interacting with RPA70, thereby preventing an inappropriate ATR activation. Our results provide a framework to understand the mechanism of regulation of ATR in human cells, which is important to prevent cellular transformation and tumorigenesis.

cancer biology↗