Biology subjects

Miller, K. M.

Publications and source records attributed to Miller, K. M..

At least 19 recordsLinked to original sources

bioRxiv2026

Kynurenine Metabolism Mediates Tumor Progression in Renal Cell Carcinoma

Renal cell carcinoma (RCC) is characterized by dysregulation of the kynurenine pathway (KP), which converts tryptophan to NAD+ while generating immunomodulatory metabolites. Therapeutic efforts have focused on inhibiting IDO1 at the pathway entry point, but the functional consequences of targeting downstream KP enzymes remain poorly characterized. We used CRISPR/Cas9 to generate knockouts of three KP enzymes in the RENCA murine RCC model--kynurenine 3-monooxygenase (KMO), quinolinic acid phosphoribosyltransferase (QPRT), and 3-hydroxyanthranilic acid dioxygenase (HAAO)--and evaluated effects on cell migration, colony formation, tumor burden, metastasis, and survival. KMO and QPRT knockouts consistently reduced migratory capacity and colony size in vitro. However, in vivo effects were distinct: while QPRT knockout reduced tumor burden, KMO knockout did not. Notably, we did not detect metastasis in female mice receiving KMO knockout RENCA cells. HAAO knockout produced divergent effects, increasing migration and colony size in vitro, but reducing tumor burden and metastasis in vivo. Mice challenged orthotopically with all three knockout cell lines had significantly extended survival compared to mice receiving wild type cells. These results indicate that individual KP enzymes exert distinct, context-dependent effects on RCC progression. The enhanced in vitro aggressiveness coupled with reduced in vivo tumorigenicity observed in HAAO knockout RENCA cells illustrates that cell culture phenotypes do not reliably predict tumor behavior, particularly when perturbing metabolic pathways with pleiotropic effects. Our findings suggest that targeting specific KP enzymes warrants further investigation as a therapeutic strategy in RCC.

cancer biology↗

bioRxiv2024

Identification of Novel Modulators of the ALT Pathway Through a Native FISH-Based Optical Screen

A significant portion of human cancers utilize a recombination-based pathway, Alternative Lengthening of Telomeres (ALT), to extend telomeres. To gain further insights into this pathway, we developed a high-throughput imaging-based screen named TAILS (Telomeric ALT In situ Localization Screen), to identify genes that either promote or inhibit ALT activity. Screening over 1000 genes implicated in DNA transactions, TAILS revealed both well-established and novel ALT modulators. We have identified new factors that promote ALT, such as the nucleosome-remodeling factor CHD4 and the chromatin reader SGF29, as well as factors that suppress ALT, including the RNA helicases DDX39A/B, the replication factor TIMELESS, and components of the chromatin assembly factor CAF1. Our data indicate that defects in histone deposition significantly contribute to ALT-associated phenotypes. Based on these findings, we demonstrate that pharmacological treatments can be employed to either exacerbate or suppress ALT-associated phenotypes.

molecular biology↗

bioRxiv2024

Alanine Scanning to Define Membrane Protein-Lipid Interaction Sites Using Native Mass Spectrometry

Lipids surrounding membrane proteins interact with different sites on the protein at varying specificities, ranging from highly specific to weak interactions. These interactions can modulate the structure, function, and stability of membrane proteins. Thus, to better understand membrane protein structure and function, it is important to identify the locations of lipid binding and the relative specificities of lipid binding at these sites. In our previous native mass spectrometry (MS) study, we developed a single and double mutant analysis approach to profile the contribution of specific residues toward lipid binding. Here, we extend this method by screening a broad range of mutants of AqpZ to identify specific lipid binding sites and by measuring binding of different lipid types to measure the selectivity of different lipids at selected binding sites. We complemented these native MS studies with molecular dynamics (MD) simulations to visualize lipid interactions at selected sites. We discovered that AqpZ is selective towards cardiolipins (CL) but only at specific sites. Specifically, CL orients with its headgroup facing the cytoplasmic side, and its acyl chains interact with a hydrophobic pocket located at the monomeric interface within the lipid bilayer. Overall, this integrative approach provides unique insights into lipid binding sites and the selectivity of various lipids towards AqpZ, enabling us to map the AqpZ protein structure based on the lipid affinity.

biophysics↗

bioRxiv2024

TRIM24 directs replicative stress responses to maintain ALT telomeres via chromatin signaling

An inability to replicate the genome can cause replication stress and genome instability. Here, we develop BLOCK-ID, a proteomic method to identify and visualize proteins at stressed replication forks. This approach successfully identified novel mediators of the replication stress response, including the chromatin acetylation reader protein TRIM24. In validating TRIM24 function, we uncovered its crucial role in coordinating Alternative Lengthening of Telomeres (ALT), a cancer-specific telomere extension pathway involving replication stress. Our data reveal that TRIM24 is directed to telomeres via a p300/CBP-dependent acetylation chromatin signaling cascade, where it organizes ALT-associated PML bodies (APBs) to promote telomere DNA synthesis. Strikingly, we demonstrate that when artificially tethered at telomeres, TRIM24 can stimulate new telomere DNA synthesis in a SUMO-dependent manner, independently of p300/CBP or PML-dependent APBs. Thus, this study identifies a TRIM24 chromatin signaling pathway required for ALT telomere maintenance.

cell biology↗

bioRxiv2024

eDNA sampling systems for salmon ecosystem monitoring

Environmental DNA (eDNA) is transforming the way aquatic ecosystems are monitored and managed by scientists, resource managers, ENGOs, First Nations communities, and citizen scientists alike. However, the lack of sampling systems enabling high filtration volumes and rapid sample collection in the field have thus far hindered broad scale eDNA studies in the ocean specifically for small and medium scale organizations. To overcome these challenges, several modular water sampling systems that utilize hollow-membrane filtration cartridges were developed by RKS laboratories and tested by the Fisheries and Oceans, Canada, Molecular Genetics Laboratory. Compared to Sterivex filters, an industry standard for eDNA filtration, the hollow-membrane filtration cartridges allowed for a six-fold increase in filtration volume and threefold increase in filtration speed. The field sampling systems, which combine pumps, a programmable controller, an air pump, an ozone generator, and up to eight filters at once, enabled efficient direct eDNA filtration from diverse aquatic environments, from creeks to the open ocean. To evaluate ease of deployment, we present the results of a three day workshop where technical staff of an Indigenous resource management organization, without any prior knowledge in eDNA sampling, were trained and performed independent eDNA sample collection. The samples were analyzed by metabarcoding and qPCR to reveal the distributions of salmon and other species co-occurring in salmon ecosystems, from large ephemeral predators, to the planktonic prey of salmon, even including their pathogens. In this example study, we further observed a substantial shift in community composition in the vicinity of aquaculture facilities where marine species associated with aquaculture feed were detected in freshwater at high relative abundance. This study demonstrates how these sampling systems provide an efficient entry point for small and medium scale organizations to utilize eDNA to fulfill their research and monitoring objectives.

genomics↗

bioRxiv2024

Hybrid Sequencing Facilitates Robust De Novo Plasmid Assembly

Despite the wide use of plasmids in research and clinical production, the need to verify plasmid sequences is a bottleneck that is too often underestimated in the manufacturing process. Although sequencing platforms continue to improve, the method and assembly pipeline chosen still influence the final plasmid assembly sequence. Furthermore, few dedicated tools exist for plasmid assembly, especially for de novo assembly. Here, we evaluated short-read, long-read, and hybrid (both short and long reads) de novo assembly pipelines across three replicates of a 24-plasmid library. Consistent with previous characterizations of each sequencing technology, short-read assemblies had issues resolving GC-rich regions, and long-read assemblies commonly had small insertions and deletions, especially in repetitive regions. The hybrid approach facilitated the most accurate, consistent assembly generation and identified mutations relative to the reference sequence. Although Sanger sequencing can be used to verify specific regions, some GC-rich and repetitive regions were difficult to resolve using any method, suggesting that easily sequenced genetic parts should be prioritized in the design of new genetic constructs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=126 SRC="FIGDIR/small/586694v2_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@13945c1org.highwire.dtl.DTLVardef@11287a8org.highwire.dtl.DTLVardef@1885654org.highwire.dtl.DTLVardef@1dbdbf3_HPS_FORMAT_FIGEXP M_FIG GRAPHICAL ABSTRACT C_FIG

synthetic biology↗

bioRxiv2024

Experimental variables that impact outcomes in Caenorhabditis elegans aging stress response

Cellular stress is a fundamental component of age-associated disease. Cells encounter various forms of stress - oxidative stress, protein misfolding, DNA damage, etc. - and respond by activating specific, well-defined stress response pathways. As we age, the burden of stress and resulting damage increases while our cells ability to deal with the consequences becomes diminished due to dysregulation of cellular stress response pathways. Many interventions that extend lifespan activate one or more stress response pathways or allow cells to maintain normal stress response later in life. The nematode Caenorhabditis elegans is a commonly used model for both aging and stress response research. As such, stress response experiments are regularly conducted as part of studies focused on mechanisms of aging in C. elegans. However, experimental design across experiments in the field are highly variable, including stressor dose, age at exposure, culture type (liquid vs. solid), bacterial strain used as a food source, and environmental temperature. These differences can result in different experimental outcomes, making comparison of results between studies challenging. Here we evaluate several experimental variables that are variable in the published literature and find that each can meaningfully alter experimental outcomes for multiple stressors. Our goal is to raise awareness of the issue of experimental variability within the field and suggest a standardized experimental design to serve as a set of guidelines for future experiments. By adopting these guidelines as a starting point, and explicitly noting differences in specific experiments, we aim to promote rigor and reproducibility, ultimately fostering more interpretable and translatable outcomes in geroscience research.

molecular biology↗

bioRxiv2023

The core microbiome of cultured Pacific oyster spat develops with age but not mortality

The Pacific oyster (Magallana gigas, also known as Crassostrea gigas) is the most widely cultured shellfish worldwide, but production has been affected by mortality events. This includes mortality events in hatcheries that can threaten the seed supply for growers. There are several pathogens that cause disease in oysters, but in many cases mortality events cannot be attributed to a single agent, and appear to be multifactorial and involve a combination of environmental variables, microbial interactions and disbiosis. In many organisms, a mature microbiome provides resilience against pathogens and environmental stressors. In this study we investigated the microbiomes of cohorts of freshly settled oyster spat, some of which experienced notable mortality. Deep sequencing of 16S rRNA gene fragments did not show a significant difference among the microbiomes of cohorts experiencing different levels of mortality, but revealed a characteristic core microbiome with 74 taxa. Irrespective of mortality, the spat core microbiomes changed significantly in the relative abundance of taxa as the spat aged; yet, remained distinct from the microbial community in the surrounding water. The core microbiome was dominated by bacteria in the families Rhodobacteraceae, Nitrosomonadaceae, Flavobacteriaceae, Pirellulaeceae and Saprospiraceae. Of these, 14 taxa were indicative for the change in the core microbiome, which we designated as the "Hard-Core Microbiome". The variability in diversity and richess of members of the core taxa decreased with oyster-spat aging, implying niche occupation. The study further accounts for the exchange of microbes with surrounding water during the core microbiome development. The observed shifts in the core microbiome with ageing oyster spat implies a crucial developmental period for the core microbiome of rearing spat. ImportanceThe Pacific oyster (Magallana gigas, also known as Crassostrea gigas) is the most widely cultivated shellfish and is important to the economy of many coastal communities. However, high mortality of spat during the first few days following metamorphosis can affect the seed supply to oyster growers. Here, we show that the microbiome composition of recently settled oyster spat experiencing low or high mortality were not significantly different. Instead, development of the core microbiome were associated with spat aging and was partially driven by dispersal through the water. These findings imply the importance of early stage rearing conditons for spat microbiome development in aquaculture facilities. Furthermore, shellfish growers could gain information about the developmental state of the oyster spat microbiome by assessing key taxa. Additionally, the study provides a baseline micriobiome for future hypothesis testing on developing spat.

microbiology↗

bioRxiv2023

The Prokaryotic and Eukaryotic Microbiome of Pacific Oyster Spat is Shaped by Ocean Warming but not Acidification

Pacific oysters (Magallana gigas, also known as Crassostrea gigas), the most widely farmed oysters, are under threat from climate change and emerging pathogens. In part, their resilience may be affected by their microbiome, which, in turn, may be influenced by ocean warming and acidification. Consequently, for three weeks, we exposed early-development Pacific oyster spat to different temperatures (18 and 24 {degrees}C) and pCO2 levels (800, 1600 and 2800 {micro}atm) in a fully crossed design. Under all conditions, the microbiome developed over time, with potentially pathogenic ciliates (Uronema marinum) greatly reduced in all treatments, suggesting that the spats microbiome undergoes adaptive shifts as the oysters age. The microbiome composition also differed significantly with temperature, but not acidification, indicating that M. gigas spat microbiomes can be altered by ocean warming but resilient to ocean acidification in our experiments. These findings highlight the spat microbiomes flexibility to environmental changes as well as its "protective" capability against potentially pathogenic microbes.

microbiology↗

bioRxiv2023

Tenacibaculosis in wild-caught, captive Chinook salmon (Oncorhynchus tshawytscha) in British Columbia, Canada

Substantial, acute mortality was observed in wild-caught Chinook salmon (Oncorhynchus tshawytscha) of various ages and sizes, from sub-adults to returning adults, held in tanks during two holding studies carried out in August and September 2022 at the Bamfield Marine Sciences Centre (BMSC), in Bamfield, British Columbia, Canada. Within days of capture, a substantial number of fish began presenting lethargy, loss of balance, abnormal swimming behavior, and skin ulcers involving the caudal peduncle, fins, belly, trunk and mouth. Molecular testing revealed high levels of Tenacibaculum dicentrarchi in skin swabs and gills, without appreciable consistent detections of other infectious agents. T. dicentrarchi was also isolated from the skin ulcers. Histological analysis confirmed the presence of ulcerative dermatitis and myositis, associated with mats of filamentous, rod-shaped bacteria. In two individuals, the infection became systemic, with a bacterial colony (identified as T. dicentrarchi) observed in the liver of one individual. In-situ hybridization against T. dicentrarchi and T. maritimum confirmed the presence of only the former agent in the gills and skin ulcers of the affected fish. This clinical report represents the first diagnosed case of tenacibaculosis in wild-caught (captive) Chinook salmon in British Columbia. CONFLICT OF INTERESTThe authors have no conflicts of interest to report. DATA AVAILABILITY STATEMENTThe data that support the findings of this study are available from the corresponding author upon reasonable request.

pathology↗

bioRxiv2022

Metatranscriptomics reveals a shift in microbial community composition and function during summer months in a coastal marine environment

Temperate coastal marine waters are often thermally stratified from spring through fall but can be dynamic and disrupted by tidal currents and wind-driven upwelling. These mixing events introduce deeper, cooler water with a higher partial pressure of CO2 (pCO2), and its associated microbial communities to the surface. Anecdotally, these events impact shellfish hatcheries and farms, warranting improved understanding of changes in composition and activity of marine microbial communities in relation to environmental processes. To characterize both compositional and functional changes associated with abiotic factors, here we generate a reference metatranscriptome from the Strait of Georgia over representative seasons and analyze metatranscriptomic profiles of the microorganisms present within intake water containing different pCO2 levels at a shellfish hatchery in British Columbia from June through October. Abiotic factors studied include pH, temperature, alkalinity, aragonite, calcite and pCO2. Community composition changes were observed to occur at broad taxonomic levels, and most notably to vary with temperature and pCO2. Functional gene expression profiles indicated a strong difference between early (June-July) and late summer (August-October) associated with viral activity. The taxonomic data suggests this could be due to the termination of cyanobacteria and phytoplankton blooms by viral lysis in the late season. Functional analysis indicated fewer differentially expressed transcripts associated with abiotic variables (e.g., pCO2) than with the temporal effect. Microbial composition and activity in these waters varies with both short-term effects observed alongside abiotic variation as well as long-term effects observed across seasons. The analysis of both taxonomy and functional gene expression simultaneously in the same samples by environmental RNA (eRNA metatranscriptomics) provided a more comprehensive view for monitoring water bodies than either would in isolation.

genetics↗

bioRxiv2021

Atlantic salmon farms are a likely source of Tenacibaculum maritimum infection in migratory Fraser River sockeye salmon

Infectious disease from domestic hosts, held for agriculture, can impact wild species that migrate in close proximity, potentially reversing selective advantages afforded by migration. For sockeye salmon in British Columbia, Canada, juveniles migrate past numerous Atlantic salmon farms from which they may acquire a number of infectious agents. We analyse patterns of molecular detection in juvenile sockeye salmon for one bacterial pathogen, Tenacibaculum maritimum, known to cause disease in fish species around the globe and to cause mouthrot disease in farmed Atlantic salmon in BC. Our data show a clear peak in T. maritimum detections in the Discovery Islands region of BC, where sockeye migrate close to salmon farms. Using well established differential-equation models to describe sockeye migration and T. maritimum infection spread, we fit models to our detection data to assess support for multiple hypotheses describing farm- and background-origin infection. Despite a data-constrained inability to resolve certain epidemiological features of the system, such as the relative roles of post infection mortality and recovery, our models clearly support the role of Discovery-Islands salmon farms in producing the observed patterns. Our best models (with 99.8% empirical model support) describe relatively constant (background) infection pressure, except around Discovery-Islands salmon farms, where farm-origin infection pressure peaked at 12.7 (approximate 95% CI: 4.5 to 31) times background levels. Given the evidence for farm-origin transfer of T. maritimum to Fraser-River sockeye salmon, the severity of associated disease in related species, and the imperilled nature of Fraser River sockeye generally, our results suggest the need for a more precautionary approach to managing farm/wild interactions in sockeye salmon.

ecology↗

bioRxiv2021

In-field genetic stock identification of overwintering coho salmon in the Gulf of Alaska: Evaluation of Nanopore sequencing for remote real-time deployment

Genetic stock identification (GSI) by single nucleotide polymorphism (SNP) sequencing has become the gold standard for stock identification in Pacific salmon, which are found in mixed-stocks during the oceanic phase of their lifecycle. Sequencing platforms currently applied require large batch sizes and multi-day processing in specialized facilities to perform genotyping by the thousands. However, recent advances in third-generation single-molecule sequencing platforms, like the Oxford Nanopore minION, provide base calling on portable, pocket-sized sequencers and hold promise for the application of real-time, in-field stock identification on variable batch sizes. Here we report and evaluate utility and comparability of at-sea stock identification of coho salmon Oncorhynchus kisutch based on targeted SNP amplicon sequencing on the minION platform during the International Year of the Salmon Signature Expedition to the Gulf of Alaska in the winter of 2019. Long read sequencers are not optimized for short amplicons, therefore we concatenate amplicons to increase coverage and throughput. Nanopore sequencing at-sea yielded stock assignment for 50 of the 80 assessed individuals. Nanopore-based SNP calls agreed with Ion Torrent based genotypes in 83.25%, but assignment of individuals to stock of origin only agreed in 61.5% of individuals highlighting inherent challenges of Nanopore sequencing, such as resolution of homopolymer tracts and indels. However, poor representation of assayed coho salmon in the queried baseline dataset contributed to poor assignment confidence on both platforms. Future improvements will focus on lowering turnaround time, accuracy, throughput, and cost, as well as augmentation of the existing baselines, specifically in stocks from coastal northern BC and Alaska. If successfully implemented, Nanopore sequencing will provide an alternative method to the large-scale laboratory approach. Genotyping by amplicon sequencing in the hands of diverse stakeholders could inform management decisions over a broad expanse of the coast by allowing the analysis of small batches in remote areas in near real-time.

genetics↗

bioRxiv2020

Poly(ADP-ribose)-binding and macroH2A mediate recruitment and functions of KDM5A at DNA lesions

The histone demethylase KDM5A removes histone H3 lysine 4 methylation, which is involved in transcription and DNA damage responses (DDR). While DDR functions of KDM5A have been identified, how KDM5A recognizes DNA lesion sites within chromatin is unknown. Here, we identify two factors that act upstream of KDM5A to promote its association with DNA damage sites. We have identified a non-canonical poly(ADP-ribose), (PAR), binding region unique to KDM5A. Loss of the PAR-binding region or treatment with PAR polymerase (PARP) inhibitors (PARPi) blocks KDM5A-PAR interactions and DNA repair functions of KDM5A. The histone variant macroH2A1.2 is also specifically required for KDM5A recruitment and functions at DNA damage sites, including homology-directed repair of DNA double-strand breaks and repression of transcription at DNA breaks. Overall, this work reveals the importance of PAR-binding and macroH2A1.2 in KDM5A recognition of damage sites that drive transcriptional and repair activities at DNA breaks within chromatin that are essential for maintaining genome integrity. SummaryThe histone demethylase KDM5A demethylates H3K4 to promote repair and transcriptional responses at DNA breaks. We identified poly(ADP-ribose)-binding and macroH2A1.2 as modulators of KDM5A association with DNA damage sites, revealing how KDM5A engages DNA breaks within chromatin.

cell biology↗

bioRxiv2020

Identification of hypoxia-specific biomarkers in salmonids using RNA-sequencing and validation using high-throughput qPCR

Identifying early gene expression responses to hypoxia (i.e., low dissolved oxygen) as a tool to assess the degree of exposure to this stressor is crucial for salmonids, because they are increasingly exposed to hypoxic stress due to anthropogenic habitat change, e.g., global warming, excessive nutrient loading, and persistent algal blooms. Our goal was to discover and validate gill gene expression biomarkers specific to the hypoxia response in salmonids across multi-stressor conditions. Gill tissue was collected from 24 freshwater juvenile Chinook salmon (Oncorhynchus tshawytscha), held in normoxia [dissolved oxygen (DO) > 8 mg L-1] and hypoxia (DO = 4{square}5 mg L-1) in 10 and 18{degrees}C temperatures for up to six days. RNA-sequencing (RNA-seq) was then used to discover 240 differentially expressed genes between hypoxic and normoxic conditions, but not affected by temperature. The most significantly differentially expressed genes had functional roles in the cell cycle and suppression of cell proliferation associated with hypoxic conditions. The most significant genes (n = 30) were selected for real-time qPCR assay development. These assays demonstrated a strong correlation (r = 0.88; p < 0.001) between the expression values from RNA-seq and the fold changes from qPCR. Further, qPCR of the 30 candidate hypoxia biomarkers was applied to an additional 322 Chinook salmon exposed to hypoxic and normoxic conditions to reveal the top biomarkers to define hypoxic stress. Multivariate analyses revealed that smolt stage, water salinity, and morbidity status were relevant factors to consider with the expression of these genes in relation to hypoxic stress. These hypoxia candidate genes will be put into application screening Chinook salmon to determine the identity of stressors impacting the fish.

genomics↗

bioRxiv2020

Direct readout of heterochromatic H3K9me3 regulates DNMT1-mediated maintenance DNA methylation

In mammals, repressive histone modifications such as trimethylation of histone H3 Lys9 (H3K9me3), frequently coexist with DNA methylation, producing a more stable and silenced chromatin state. However, it remains elusive how these epigenetic modifications crosstalk. Here, through structural and biochemical characterizations, we identified the replication foci targeting sequence (RFTS) domain of maintenance DNA methyltransferase DNMT1, a module known to bind the ubiquitylated H3 (H3Ub), as a specific reader for H3K9me3/H3Ub, with the recognition mode distinct from the typical trimethyl-lysine reader. Disruption of the interaction between RFTS and the H3K9me3Ub affects the localization of DNMT1 in stem cells and profoundly impairs the global DNA methylation and genomic stability. Together, this study reveals a previously unappreciated pathway through which H3K9me3 directly reinforces DNMT1-mediated maintenance DNA methylation.

genetics↗

bioRxiv2020

Emerging viruses in British Columbia salmon discovered via a viral immune response biomarker panel and metatranscriptomic sequencing

The emergence of infectious agents poses a continual economic and environmental challenge to aquaculture production, yet the diversity, abundance and epidemiology of aquatic viruses are poorly characterised. In this study, we applied salmon host transcriptional biomarkers to identify and select fish in a viral disease state but only those that we also showed to be negative for established viruses. This was followed by metatranscriptomic sequencing to determine the viromes of dead and dying farmed Atlantic (Salmo salar) and Chinook (Oncorhynchus tshawytscha) salmon in British Columbia. We found that the application of the biomarker panel increased the probability of discovering viruses in aquaculture populations. We discovered viruses that have not previously been characterized in British Columbian Atlantic salmon farms. To determine the epidemiology of the newly discovered or emerging viruses we conducted high-throughput RT-PCR to reveal their prevalence in British Columbia (BC), and detected some of the viruses we first discovered in farmed Atlantic salmon in Chinook and sockeye salmon, suggesting a broad host range. Finally, we applied in-situ hybridisation to confirm infection and explore the tissue tropism of each virus.

genomics↗

bioRxiv2020

Developmental exposure to the organochlorine pesticide dieldrin causes male-specific exacerbation of α-synuclein-preformed fibril-induced toxicity and motor deficits

Human and animal studies have shown that exposure to the organochlorine pesticide dieldrin is associated with increased risk of Parkinsons disease (PD). Previous work showed that developmental dieldrin exposure increased neuronal susceptibility to MPTP toxicity in male C57BL/6 mice, possibly via changes in dopamine (DA) packaging and turnover. However, the relevance of the MPTP model to PD pathophysiology has been questioned. We therefore studied dieldrin-induced neurotoxicity in the -synuclein (-syn)-preformed fibril (PFF) model, which better reflects the -syn pathology and toxicity observed in PD pathogenesis. Specifically, we used a "two-hit" model to determine whether developmental dieldrin exposure increases susceptibility to -syn PFF-induced synucleinopathy. Dams were fed either dieldrin (0.3 mg/kg, every 3-4 days) or vehicle corn oil starting 1 month prior to breeding and continuing through weaning of pups at postnatal day 22. At 12 weeks of age, male and female offspring received intrastriatal PFF or control saline injections. Consistent with the male-specific increased susceptibility to MPTP, our results demonstrate that developmental dieldrin exposure exacerbates PFF-induced toxicity in male mice only. Specifically, in male offspring, dieldrin exacerbated PFF-induced motor deficits on the challenging beam and increased DA turnover in the striatum 6 months after PFF injection. However, male offspring showed neither exacerbation of phosphorylated -syn (pSyn) aggregation in the substantia nigra (SN) at 1 or 2 months post-PFF injection, nor exacerbation of PFF-induced TH and NeuN loss in the SN 6 months post-PFF injection. Collectively, these data indicate that developmental dieldrin exposure produces a male-specific increase in neuronal vulnerability to synucleinopathy. This sex-specific result is consistent with both previous work in the MPTP model, our previously reported sex-specific effects of this exposure paradigm on the male and female epigenome, and the higher prevalence and more severe course of PD in males. The novel two-hit environmental toxicant/PFF exposure paradigm established in this project can be used to explore the mechanisms by which other PD-related exposures alter neuronal vulnerability to synucleinopathy in sporadic PD. HighlightsO_LIDevelopmental dieldrin exposure increases -syn-PFF-induced motor deficits C_LIO_LIDevelopmental dieldrin exposure increases PFF-induced deficits in DA handling C_LIO_LIDevelopmental dieldrin exposure does not affect PFF-induced loss of nigral neurons C_LIO_LIThis is a novel paradigm modeling how environmental factors increase risk of PD C_LIO_LIFemale mice show PFF-induced pathology, but no PFF-induced motor deficits. C_LI

neuroscience↗