Biology subjects

Fowler, A.

Publications and source records attributed to Fowler, A..

17 recordsLinked to original sources

bioRxiv2025

Environmental gradients decouple demographic and adaptive connectivity in a highly mobile coastal marine species

Understanding how eco-evolutionary processes shape genetic variation and persistence in marine species with highly variable recruitment dynamics and dispersal potential remains a fundamental challenge, particularly when considering the interplay between gene flow and local adaptation. Here, we employed a seascape genomics approach to investigate population connectivity and local adaptation in Australasian snapper (Chrysophrys auratus, Sparidae) along 1500 km of the environmentally heterogeneous southern Australian coastline. Using 14,699 SNPs, we identified two distinct regional populations aligned with known biogeographical regions. Genotype-environment association analyses revealed 855 candidate adaptive loci associated with environmental variation, including temperature, salinity, and primary productivity. Connectivity analyses using neutral markers indicated high gene flow throughout both eastern and western regions, while candidate adaptive loci revealed substantially reduced connectivity, especially for Northern Spencer Gulf and West Coast populations. This pattern of locally restricted gene flow at adaptive genomic regions suggests that strong environmental gradients are driving adaptive divergence despite high overall connectivity. Our results support contingent migration as a potential mechanism modulating the balance between local adaptation and gene flow in this economically and ecologically important marine species. These findings might also have implications for regional management of other coastal fisheries that are experiencing substantial declines. As climate change alters coastal marine environments around the world, the dynamics of local recruitment, site fidelity and local adaptation are expected to change. This highlights the importance of integrating knowledge about eco-evolutionary processes into marine resource management, fisheries stock assessment, and restocking and stock enhancement activities.

ecology↗

bioRxiv2025

Leveraging autophagy and pyrimidine metabolism to target pancreatic cancer

Autophagy inhibitors are promising compounds to treat pancreatic ductal adenocarcinoma (PDA) but their efficacy in patients is unclear, highlighting a need to understand mechanisms of resistance. We used a novel approach to uncover metabolic adaptations that bypass autophagy inhibition. Utilizing PDA cells with acquired resistance to different autophagy inhibitors, we found that severe autophagy depletion induces metabolic rewiring to sustain TCA intermediates and nucleotides for biosynthesis. Long-term autophagy inhibition results in altered pyruvate metabolism likely regulated by lower pyrimidine pools. Cells adapting to loss of autophagy preferentially salvage pyrimidines to replenish these pools instead of synthesizing them de novo. Exploiting this metabolic vulnerability, we found that acquired resistance to autophagy inhibition promotes increased salvage and therefore sensitivity to pyrimidine analogues, including gemcitabine and trifluridine/tipiracil leading to combinatory effects with autophagy inhibitors and pyrimidine analogs. These studies provide mechanistic insight defining how autophagy inhibition can be leveraged to treat pancreatic cancer.

cancer biology↗

bioRxiv2025

A Multi-Model Ensemble Reveals Soil Carbon Gains from Regenerative Practices in the U.S. Midwest Cropland

Process-based cropping systems models (CSMs) are key components of measurement, monitoring, reporting, and verification (MMRV) frameworks of carbon markets, but their application suffers from model-specific differences that keep any one model from working well across all combinations of soils, climates, crops, and agronomic practices at varying scales. Multi-model ensemble (MME), successfully used to quantify soil, management and climate impact on crop productivity, provide an opportunity to better estimate changes in soil organic carbon (SOC) outcomes for agronomic practices that have the potential to mitigate SOC loss at scale. We used an MME across 46 million hectares of US Midwest cropland at a resolution of 4- km2 to assess the aggregate ability of different regenerative practices to sequester SOC at this scale compared to their dynamic baselines. MME was validated with long-term experimental data and compared to its constituent CSMs, showing greater accuracy and lower uncertainty. The results show that adopting no-till combined with cover crops increased SOC stocks by 0.36 {+/-} 0.12 Mg ha-1 yr-1 aggregated across the entire U.S. Midwest cropland. At the regional scale, this corresponds to a net SOC gain of 16.4 Tg C yr-1 compared to business-as-usual baselines. These benefits are approximately halved when each management change is practiced individually, and the modest gains are only fully realized when continued over the long-term in soils with low initial carbon stock. Results demonstrate the power of MMEs run at high resolution for providing robust estimates of environmental outcomes following agricultural practice change, and for pinpointing locations for most effective intervention. This approach can alleviate many producer carbon market participation barriers and help address market issues while ultimately supporting large-scale regenerative agriculture initiatives.

ecology↗

bioRxiv2025

Sustained efficacy of CRISPR-Cas13b gene therapy for FSHD is challenged by immune response to Cas13b

Facioscapulohumeral muscular dystrophy (FSHD) is a potentially devastating muscle disease caused by de-repression of the toxic DUX4 gene in skeletal muscle. FSHD patients may benefit from DUX4 inhibition therapies, and although several experimental strategies to reduce DUX4 levels in skeletal muscle are being developed, no approved disease modifying therapies currently exist. We developed a CRISPR-Cas13b system that cleaves DUX4 mRNA and reduces DUX4 protein level, protects cells from DUX4-mediated death, and reduces FSHD-associated biomarkers in vitro. In vivo delivery of the CRISPR-Cas13b system with adeno-associated viral vectors reduced acute damage caused by high DUX4 levels in a mouse model of severe FSHD. However, protection was not sustained over time, with decreases in Cas13b and guide RNA levels between 8 weeks and 6 months after injection. In addition, wild-type mice injected with AAV6.Cas13b showed muscle inflammation with infiltrates containing Cas13b-responsive CD8+ cytotoxic T cells. Our RNA-seq data confirmed that several immune response pathways were significantly increased in human FSHD myoblasts transfected with Cas13b. Overall, our findings suggest that CRISPR-Cas13b is highly effective for DUX4 silencing but successful implementation of CRISPR/Cas13-based gene therapies may require strategies to mitigate immune responses.

molecular biology↗

bioRxiv2024

Evaluating the utility of amino acid similarity-aware kmers to represent TCR repertoires for classification

Insights gained through interpretation of models trained on the T-cell receptor (TCR) repertoire contribute to advances in understanding of immune-mediated disease. This has the potential to improve diagnostic tests and treatments, particularly for autoimmune diseases. However, TCR repertoire datasets with samples from donors of known autoimmune disease status generally include orders of magnitude fewer samples than TCR sequences. Promising TCR repertoire classification approaches consider relationships between non-identical TCR sequences. In particular, kmer methods demonstrate strong and stable performance for small datasets. We propose a TCR repertoire representation that considers the relationships between amino acids within kmers flexibly and efficiently, which makes exploration of a wide range of TCR sequence features feasible. XGBoost models are trained and tested on kmer representations of TCR repertoire datasets including samples from patients with coeliac disease as well as donors with previous cytomegalovirus infection. We show that kmers that use small representative alphabets of amino acids are capable of training models that perform similarly or better than kmers based on all 20 amino acids. We find that, for cytomegalovirus infection status classification, defining amino acid relationships using BLOSUM62 can lead to a model with stronger performance as compared to an Atchley factor definition. Finally, we detail kmers or motifs which are important in each classification model and highlight the challenge of training truly interpretable TCR repertoire classification models which, if overcome, could lead to biomarker discovery for autoimmune diseases. Author summaryTCR repertoire classification models can provide valuable understanding of autoimmune diseases if they can accurately infer autoimmune disease status and are biologically interpretable. Based on a kmer representation of the TCR repertoire, which has been shown to be most appropriate to train classification models on smaller datasets, we develop a computationally efficient method of grouping amino acid sequences to add knowledge to immune status classification model inputs, and consider its effect on interpretability. We find that most of the 4mer-based feature types we tested perform well in combination with an XGBoost model, where some benefit may be gained by applying a greatly-reduced alphabet of amino acids based on BLOSUM62 for cytomegalovirus serostatus classification. Our proposed reduced alphabet methodology is an alternative to kmer clustering which allows more efficient exploration of amino acid relationships and results in a more interpretable feature space.

immunology↗

bioRxiv2024

Identification of molecular and functional subtypes using chronic pancreatitis patient-derived organoid models

Chronic pancreatitis (CP) affects [~]3 million people worldwide, yet altering the course of disease is challenging. We developed a patient-derived organoid (PDO) platform to investigate the molecular pathogenesis of this disease and identify therapeutic strategies. We generated 36 PDOs from patients with idiopathic, hereditary, and alcohol-related CP with high genetic concordance. PDOs retained inflammation-associated transcriptional and proteomic features. Transcriptomic profiling revealed three molecular subtypes of CP independent of etiology. We discovered widespread dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) in half of the CP PDOs, including those with wildtype CFTR. Clinically available CFTR modulators stabilized mutant or wildtype CFTR, restored CFTR function, and decreased mitogenic and inflammatory signaling. This work provides the first comprehensive PDO platform for modeling CP. We demonstrate the utility of this platform for precision therapeutic investigations. Our findings reveal CFTR modulators as a broadly applicable and effective therapeutic strategy.

cell biology↗

bioRxiv2024

Individual performance niches may buffer population responses to climate change in estuarine fishes

Climate change may impact individual organisms in different ways, a consideration often overshadowed by predominant focus on population effects in studies. We examined three estuarine fish species to determine if individual fish performance, persisted across winter water temperatures. Fish performance at 16{degrees}C (current Sydney winter estuarine water temperature) and 20{degrees}C (predicted under climate change) with low and high food regimes was assessed using key physiological (growth, aerobic scope, burst speed) and behavioural parameters (foraging activity, boldness, shelter usage, predator escape response). We expected a strong positive relationship between performance at 16{degrees}C and 20{degrees}C for each parameter, and interactions with food level, however in general this was not found for any species. Relative performance was only maintained across temperatures for a few parameters, such as bite rate, boldness, and shelter response in one species (trumpeter Pelates sexlineatus), with aerobic scope in silver biddy Gerres subfasciatus, and boldness in fortescue Centropogon australis. Our results suggest that individuals fitness (directly via changes in growth, indirectly via behaviours) will be impacted by climate warming due to differences in relative performance among individuals across water temperatures. Changes in relative performance among individuals may initially compensate for a population-level response, thereby buffering the effects of climate change.

ecology↗

bioRxiv2023

Glioma Cells Secrete Collagen VI to Facilitate Invasion

While glioblastoma (GBM) progression is associated with extensive extracellular matrix (ECM) secretion, the causal contributions of ECM secretion to invasion remain unclear. Here we investigate these contributions by combining engineered materials, proteomics, analysis of patient data, and a model of bevacizumab-resistant GBM. We find that GBM cells cultured in engineered 3D hyaluronic acid hydrogels secrete ECM prior to invasion, particularly in the absence of exogenous ECM ligands. Proteomic measurements reveal extensive secretion of collagen VI, and collagen VI-associated transcripts are correspondingly enriched in microvascular proliferation regions of human GBMs. We further show that bevacizumab-resistant GBM cells deposit more collagen VI than their responsive counterparts, which is associated with marked cell-ECM stiffening. COL6A3 deletion in GBM cells reduces invasion, {beta}-catenin signaling, and expression of mesenchymal markers, and these effects are amplified in hypoxia. Our studies strongly implicate GBM cell-derived collagen VI in microenvironmental remodeling to facilitate invasion.

bioengineering↗

bioRxiv2023

Patient phenotypes and their relation to TNFα signaling and immune cell composition in critical illness and autoimmune disease

RationaleTNF inhibitors have shown promise in reducing mortality in hospitalized COVID-19 patients; one hypothesis explaining the limited clinical efficacy is patient heterogeneity in the TNF pathway. MethodsWe evaluated the effect of TNF inhibitors in a mouse model of LPS-induced acute lung injury. Using machine learning we attempted predictive enrichment of TNF signaling in patients with either ARDS or sepsis. We examined biological factors that drive heterogeneity in host responses to critical infection and their relation to clinical outcomes. ResultsIn mice, LPS induced TNF-dependent neutrophilia, alveolar permeability and endothelial injury. In humans, TNF pathway activation was significantly increased in peripheral blood of patients with critical illnesses and associated with the presence of mature neutrophils across critical illnesses and several autoimmune conditions. Machine learning using a gene signature separated patients into 5 phenotypes; one was a hyper-inflammatory, interferon-associated phenotype enriched for increased TNF pathway activation and conserved across critical illnesses and autoimmune diseases. Cell subset profiles segregated severely ill patients into neutrophil-subset-dependent groups that were enriched for disease severity, demonstrating the importance of neutrophils in the immune response in critical illness. ConclusionsTNF signaling and mature neutrophils are associated with a hyper-inflammatory phenotype of patients, shared across critical illness and autoimmune disease. This phenotyping provides a personalized medicine hypothesis to test anti-TNF therapy in severe respiratory illness. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/564631v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@1e25724org.highwire.dtl.DTLVardef@c708bcorg.highwire.dtl.DTLVardef@10e7531org.highwire.dtl.DTLVardef@3014b8_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2023

A Virus-like particle-based bivalent PCSK9 vaccine lowers LDL-cholesterol levels in Non-Human Primates

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor in the development of atherosclerotic cardiovascular disease (ASCVD). Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDL-C metabolism, have emerged as promising approaches for reducing elevated LDL-C levels. Here, we evaluated the cholesterol lowering efficacy of virus-like particle (VLP) based vaccines that target epitopes found within the LDL receptor (LDL-R) binding domain of PCSK9. In both mice and non-human primates, a bivalent VLP vaccine targeting two distinct epitopes on PCSK9 elicited strong and durable antibody responses and lowered cholesterol levels. In macaques, a VLP vaccine targeting a single PCSK9 epitope was only effective at lowering LDL-C levels in combination with statins, whereas immunization with the bivalent vaccine lowered LDL-C without requiring statin co-administration. These data highlight the efficacy of an alternative, vaccine-based approach for lowering LDL-C.

immunology↗

bioRxiv2023

Bioregional boundaries and genomically-delineated stocks in snapper (Chrysophrys auratus) from southeastern Australia

Marine species often exhibit genetic discontinuities concordant with biogeographic boundaries, frequently occurring due to changes in ocean circulation, bathymetry, coastline topography and temperature. Here we used 10,916 single nucleotide polymorphisms (SNPs) to assess the concordance between population genomic differentiation and coastal biogeography in the fishery important snapper (Chrysophrys auratus) across southeastern Australia. Additionally, we investigated whether spatial scales of assessment and management of snapper align with evidence from population genomics. Across 488 snapper samples from 11 localities between the west coast of South Australia and the south coast of New South Wales, we detected genomic structure concordant with the regions three biogeographic provinces. We also detected fine-scale genetic structuring relating to spatial variation in spawning and recruitment dynamics, as well as temporal stability in the genomic signal associated with two important spawning grounds. The current management boundaries in the region coincided with either the genetic breaks at bioregional boundaries or with localscale variation. Our study highlights the value of population genomic surveys in species with high dispersal potential for uncovering stock boundaries and demographic variation related to spawning and recruitment. It also illustrates the importance of marine biogeography in shaping population structure in commercial species with high dispersal potential.

genomics↗

bioRxiv2022

Fisheries genomics of snapper (Chrysophrys auratus) along the western Australian coast

The efficacy of fisheries management strategies depends on stock assessment and management actions being carried out at appropriate spatial scales. This requires understanding of spatial and temporal population structure and connectivity, which is challenging in weakly structured and highly connected marine populations. We carried out a population genomics study of the heavily exploited snapper (Chrysophrys auratus) along [~]2,600 km of the Australian coastline, with a focus on Western Australia (WA). We used 10,903 filtered SNPs in 341 individuals from eight locations to characterise population structure and connectivity in snapper across WA and to assess if current spatial scales of stock assessment and management agree with evidence from population genomics. Our dataset also enabled us to investigate temporal stability in population structure as well as connectivity between WA and its nearest, eastern jurisdictional neighbor. As expected for a species influenced by the extensive ocean boundary current in the region, low genetic differentiation and high connectivity was uncovered across WA. However, we did detect strong isolation by distance and genetic discontinuities in the mid-west and south-east. The discontinuities correlate with boundaries between biogeographic regions, influenced by on-shelf oceanography, and the sites of important spawning aggregations. We also detected temporal instability in genetic structure at one of our sites, possibly due to interannual variability in recruitment in adjacent regions. Our results partly contrast with the current spatial management of snapper in WA, highlighting the need for a review. This study supports the value of population genomic surveys in informing the management of weakly-structured and wide-ranging marine fishery resources.

genomics↗

bioRxiv2021

A VLP-based vaccine targeting ANGPTL3 lowers plasma triglycerides in mice

Elevated triglycerides (TGs) are an important risk factor for the development of coronary heart disease (CHD) and in acute pancreatitis. Angiopoietin-like proteins 3 (ANGPTL3) and 4 (ANGPTL4) are critical regulators of TG metabolism that function by inhibiting the activity of lipoprotein lipase (LPL), which is responsible for hydrolyzing triglycerides in lipoproteins into free fatty acids. Interestingly, individuals with loss-of-function mutations in ANGPTL3 and ANGPTL4 have low plasma TG levels, have a reduced risk of CHD, and are otherwise healthy. Consequently, interventions targeting ANGPTL3 and ANGPTL4 have emerged as promising new approaches for reducing elevated TGs. Here, we developed virus-like particle (VLP) based vaccines that target the LPL binding domains of ANGPTL3 and ANGPTL4. ANGPTL3 VLPs and ANGPTL4 VLPs are highly immunogenic in mice and vaccination with ANGPTL3 VLPs, but not ANGPTL4 VLPs, was associated with reduced steady state levels of TGs. Immunization with ANGPTL3 VLPs rapidly cleared circulating TG levels following an oil gavage challenge and enhanced plasma LPL activity. These data indicate that targeting ANGPTL3 by active vaccination is potential alternative to other ANGPTL3-inhibiting therapies. HighlightsO_LIANGPTL3 and ANGPTL4 are mediators of lipoprotein metabolism that inhibit lipoprotein lipase (LPL) activity. C_LIO_LIVaccination using virus-like particles (VLPs) targeting ANGPTL3 and ANGPTL4 elicits high-titer IgG antibody responses. C_LIO_LIImmunization with ANGPTL3 VLPs lowers steady-state plasma triglycerides and enhances LPL activity. C_LI

immunology↗

bioRxiv2020

Predicting the animal hosts of coronaviruses from compositional biases of spike protein and whole genome sequences through machine learning

The COVID-19 pandemic has demonstrated the serious potential for novel zoonotic coronaviruses to emerge and cause major outbreaks. The immediate animal origin of the causative virus, SARS-CoV-2, remains unknown, a notoriously challenging task for emerging disease investigations. Coevolution with hosts leads to specific evolutionary signatures within viral genomes that can inform likely animal origins. We obtained a set of 650 spike protein and 511 whole genome nucleotide sequences from 225 and 187 viruses belonging to the family Coronaviridae, respectively. We then trained random forest models independently on genome composition biases of spike protein and whole genome sequences, including dinucleotide and codon usage biases in order to predict animal host (of nine possible categories, including human). In hold-one-out cross-validation, predictive accuracy on unseen coronaviruses consistently reached [~]73%, indicating evolutionary signal in spike proteins to be just as informative as whole genome sequences. However, different composition biases were informative in each case. Applying optimised random forest models to classify human sequences of MERS-CoV and SARS-CoV revealed evolutionary signatures consistent with their recognised intermediate hosts (camelids, carnivores), while human sequences of SARS-CoV-2 were predicted as having bat hosts (suborder Yinpterochiroptera), supporting bats as the suspected origins of the current pandemic. In addition to phylogeny, variation in genome composition can act as an informative approach to predict emerging virus traits as soon as sequences are available. More widely, this work demonstrates the potential in combining genetic resources with machine learning algorithms to address long-standing challenges in emerging infectious diseases.

genomics↗

bioRxiv2020

Growth impacts in a changing ocean: insights from two coral reef fishes in an extreme environment

Determining the life history consequences for fishes living in extreme and variable environments will be vital in predicting the likely impacts of ongoing climate change on reef fish demography. Here, we compare size-at-age and maximum body size of two common reef fish species (Lutjanus ehrenbergii and Pomacanthus maculosus) between the environmentally extreme Arabian/Persian Gulf (‘Arabian Gulf’) and adjacent comparably benign Oman Sea. Additionally, we use otolith increment width profiles to investigate the influence of temperature, salinity and productivity on the individual growth rates. Individuals of both species showed smaller size-at-age and lower maximum size in the Arabian Gulf compared to conspecifics in the less extreme and less variable environment of the Oman Sea, suggesting a life-history trade-off between size and metabolic demands. Salinity was the best environmental predictor of interannual growth across species and regions, with low growth corresponding to more saline conditions. However, salinity had a weaker negative effect on interannual growth of fishes in the Arabian Gulf than in the Oman Sea, indicating Arabian Gulf populations may be better able to acclimate to changing environmental conditions. Temperature had a weak positive effect on the interannual growth of fishes in the Arabian Gulf, suggesting that these populations may still be living within their thermal windows. Our results highlight the potential importance of osmoregulatory cost in impacting growth, and the need to consider the effect of multiple stressors when investigating the consequences of future climate change on fish demography.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2019

Reduced Plasma Ascorbic Acid Levels in Recipients of Myeloablative Conditioning & Hematopoietic Cell Transplantation

Hematopoietic cell transplantation (HCT) conditioned using myeloablative conditioning (MAC) is complicated by end organ injury due to endothelial dysfunction and graft versus host disease. Mucositis and oxidant injury results in micronutrient deficiency. Ascorbic acid (AA) levels were measured in 15 patients undergoing HCT conditioned with MAC (11 allogeneic and 4 autologous HCT). Ascorbate levels declined post conditioning to 27.3 ({+/-}14.1) by day 0 (p <0.05 compared with baseline), reaching a nadir level of 21.5 ({+/-}13.8) on day 14 (p <0.05) post-transplant. Patients undergoing allogeneic HCT continued to have low AA levels to day 60 post transplant, whereas recipients of autologous HCT recovered plasma AA levels to normal. The role of AA in maintaining endothelial function and hematopoietic as well as T cell recovery is provided, developing the rationale for repletion of vitamin C following HCT.

physiology↗

bioRxiv2018

Inferring B cell specificity for vaccines using a mixture model

Vaccines have greatly reduced the burden of infectious disease, ranking in their impact on global health second only after clean water. Most vaccines confer protection by the production of antibodies with binding affinity for the antigen, which is the main effector function of B cells. This results in short term changes in the B Cell receptor (BCR) repertoire when an immune response is launched, and long term changes when immunity is conferred. Analysis of antibodies in the serum is usually used to evaluate vaccine response, however this is limited and therefore the investigation of the BCR repertoire provides far more detail for the analysis of vaccine response. Here, we introduce a novel Bayesian model to describe the observed distribution of BCR sequences and the pattern of sharing across time and between individuals, with the goal to identify vaccine-specific BCR sequences. We use data from two studies to assess the model and estimate that we can identify vaccine-specific sequences with 69% sensitivity.

genomics↗