Biology subjects

Bernier, N. J.

Publications and source records attributed to Bernier, N. J..

5 recordsLinked to original sources

bioRxiv2026

Transcriptional regulation of the rainbow trout spleen corticotropin-releasing factor system in response to inflammatory challenges: roles of NF-kB and cortisol

The corticotropin-releasing factor (CRF) system bidirectionally interacts with cytokines and other immune-related components in mammals. However, the nature of these interactions remains poorly characterized in other vertebrates, including teleost fishes. To gain insight into the relationship between immune responses and the CRF system in teleosts, we explored how CRF system components were transcriptionally regulated in immune organs of rainbow trout (Oncorhynchus mykiss). We first characterized the CRF system in the spleen and head kidney--two primary immune organs in teleosts--and found that many CRF system components were present in both tissues, but splenic expression was consistently greater. Changes in the abundance of splenic CRF system components following vaccination (which transiently stimulated inflammatory responses and cytokine production) indicated contrasting and time-dependent regulation of CRF receptor 1 (CRFR1; suppression) and CRFR2 (stimulation) activities in response to an inflammatory challenge. Using spleen explant cultures, we then evaluated whether these effects were mediated by either of nuclear factor kappa B (NF-{kappa}B; a pro-inflammatory transcription factor) or cortisol (an anti-inflammatory hormone). At baseline, cultured spleens increased cytokine production and exhibited transcriptional changes in CRF system components comparable to those observed following vaccination. Cortisol treatment and NF-{kappa}B inhibition both attenuated the rise in cytokine transcription; however, cortisol treatment generally affected transcripts influencing CRFR1 activity, while NF-{kappa}B inhibition reduced CRFR2 activity. Overall, our data provide novel insight into CRF system regulation in the spleen and suggest that cortisol and inflammatory cytokines differentially regulate CRFR1 and CRFR2 activity within this organ.

physiology↗

bioRxiv2026

Stressor- and tissue-specific regulation of the corticotropin-releasing factor system across epithelial tissues in rainbow trout

The corticotropin-releasing factor (CRF) system is a major neural regulator of stress responses in vertebrates. However, stress-related roles for the CRF system in other tissues--and whether these roles vary between stressor types--remain unclear. To address this gap, we first characterized the CRF system in the gills and intestine of rainbow trout (Oncorhynchus mykiss) and then evaluated how it is transcriptionally regulated following either an immune (vaccination) or osmotic (seawater transfer) stressor. Additionally, since the CRF system is involved in food intake regulation, we also evaluated whether feeding state affects the intestinal CRF system. Vaccination against Vibrio anguillarum reduced CRF system activity in the intestine--as indicated by elevations in CRF binding protein transcripts paired with reductions in ligand (crfa2) and receptor (crfr1b) transcripts--but did not affect the gill CRF system. In contrast, seawater transfer caused the abundance of most CRF system transcripts to increase in the middle (but not posterior) portion of the intestine, while transcript levels of CRF binding proteins and receptors in the gills declined. Finally, levels of CRF system transcripts in the intestine varied with feeding state in a region-specific manner. In the middle intestine, transcript levels of most components declined with fasting and increased when feeding was resumed, whereas the opposite pattern occurred in the posterior intestine. Overall, our results implicate the peripheral CRF system as a stressor- and epithelial tissue-specific modulator of immune and osmoregulatory functions in teleosts.

physiology↗

bioRxiv2025

High-throughput multispecies qPCR assays to study the effects of acute thermal stress in three species of Acipenser sturgeon

In this study, we developed a multispecies OpenArray qPCR "chip" to measure the effects of acute thermal stress on the mRNA response of Acipenser sturgeons. The qPCR chips were then tested on three species: Acipenser fulvescens, Acipenser oxyrinchus oxyrinchus, and Acipenser brevirostrum. The A. fulvescens were from two genetically distinct populations (Burntwood River and Winnipeg River, Manitoba, Canada) that were acclimated to three different temperatures (16, 20, and 24 {degrees}C) to quantify the effects of genetic background and acclimation temperatures on the transcriptomic response to acute thermal stress. Additionally, juvenile A. oxyrinchus oxyrinchus and A. brevirostrum were acclimated to 10 {degrees}C and then experienced acute thermal stress. All three species were sampled for gill and liver before and after experiencing acute thermal stress, which was applied using a CTmax test. The expression of 52 genes of interest was quantified using the multispecies qPCR chip for all three species, along with 4 reference genes. We showed that acute thermal stress affected the mRNA expression of 17-26 of the thermal metabolic stress genes that were assayed using the chip, depending on the species. However, the mRNA patterns varied between species and genetically distinct populations.

physiology↗

bioRxiv2024

Regulation of a unique neuroendocrine complex by environmental salinity in salmonid fishes

The caudal neurosecretory system (CNSS) is a fish-specific neuroendocrine complex whose function(s) remain uncertain despite 60+ years of research. Osmoregulatory roles for the CNSS have been hypothesized, but molecular regulation of the CNSS following changes in environmental salinity remains poorly characterized. Therefore, we performed transcriptomics on the CNSS of rainbow trout (Oncorhynchus mykiss) to establish: 1) how the CNSS responds following seawater (SW) transfer, and 2) which endocrine systems contribute to osmoregulatory responses in the CNSS. Responses following SW transfer varied at 24 h versus 168 h, with changes primarily affecting membrane transport and transcriptional processes at 24 h and neuronal processes at 168 h. Components of several osmoregulation-associated endocrine systems were affected (e.g., corticosteroids), including some which have not previously been identified in the CNSS (e.g., calcitonin). Additionally, transcript levels of corticotropin-releasing factor (CRF) peptides--which have osmoregulatory functions and were highly abundant in the CNSS--were [~]2-fold higher after 24 h in SW. Therefore, we performed additional experiments investigating CRF peptides in a more euryhaline salmonid, Atlantic salmon (Salmo salar). Smolts had up to 12-fold higher levels of CRF peptide transcripts than parr, but abundance declined following SW transfer. Additionally, CRF transcripts were lower 24 h following freshwater transfer of SW-acclimated salmon. These results suggest that CRF peptides acutely aid in coordinating physiological responses following fluctuations in environmental salinity via anticipatory and/or responsive mechanisms. Collectively, our data indicate that CNSS-mediated production of CRF peptides has osmoregulatory functions and provide a resource for investigations of novel CNSS functions.

zoology↗

bioRxiv2024

Development of multi-species qPCR assays for a stress transcriptional profiling (STP) Chip to assess the resilience of salmonids to changing environments

Ecologically and socio-economically important salmonid fishes in Canada are threatened by diverse environmental stressors. However, predicting species responses to environmental change requires understanding the underlying molecular mechanisms governing environmental stress tolerance. Developing advanced molecular genetic tools will provide opportunities to predict how salmonid fishes will respond to environmental stressors and assess their adaptive potential and vulnerability into the future. Here, we developed a panel of Taqman quantitative PCR (qPCR) assays designed to measure mRNA transcript abundance at selected candidate loci for use across salmonids. We designed and applied those assays for use in a high-throughput nanofluidic OpenArray Stress Transcriptional Profiling Chip (STP-Chip) capable of 2688 simultaneous qPCR at multiple gene loci (112 targets for 12 samples in duplicate). Using the nanofluidic STP-Chip, we tested these 112 multi-species qPCR assays using gill, liver and muscle tissue from eight species of salmonids across four genera. Of the selected 112 assays, 69 assays showed amplification in gill, 64 in liver, and 67 in muscle across all eight salmonid species. The percentage of assays that showed amplification across three tissues varied between genera: In general, Salmo, Oncorhynchus, and Salvelinus species showed a higher success rate than Coregonus species. Stress, circadian rhythm, apoptosis, growth-metabolism, and detoxification-relevant assays showed high success rates for amplification across all salmonid species for all three tissues. In contrast, neural plasticity, appetite regulation, osmoregulation, immune function, endocrine disruption, and hypoxia-relevant assays showed low success. Not surprisingly, we observed tissue-specific variation among qPCR amplification patterns. There were significant differences in mRNA transcript abundance among species across the four genera, but we did not see variation between species from the same genus. These qPCR assays can be used to design custom STP-Chips that can be used for quantifying stress in salmonid fish, improving health through more accurate diagnostic tests for disease, and monitoring adaptation to accelerated climate change regionally and globally.

genomics↗