Biology subjects

Heath, D. D.

Publications and source records attributed to Heath, D. D..

4 recordsLinked to original sources

bioRxiv2026

Gene transcriptional profiling to assess Chinook salmon osmoregulatory resilience to salinity challenges

Given unprecedented environmental change, Pacific salmonids are becoming increasingly threatened; however, genomic technologies provide an opportunity to assess Pacific salmonid resilience to on-going environmental change. Also, given increasing conservation and animal welfare concerns, non-lethal tissue sampling is emerging for assessing the physiological status of wild species. Relatively few studies, however, have compared the transcriptomic response of fish sampled non-lethally versus lethally for fish health and stress quantification. Here, we conducted a comparative gene transcriptional profiling study using 28 qPCR assays on the OpenArray platform as an osmoregulatory stress transcriptional profiling chip. We sampled both non-lethal (gill biopsies, skin swabs, and water [eRNA]) and lethal (whole gill and liver) tissue samples from Chinook salmon (Oncorhynchus tshawytscha) smolts exposed for 0 h, 24 h, and 72 h to freshwater (0 PSU), brackish water (15 PSU) or seawater (30 PSU). We observed that most assays showed higher qPCR amplification success in both non-lethal gill biopsies and lethal gill tissues, compared to other tissues. We found more significant differences in transcript abundance in traditional lethal tissues compared to non-lethal tissues. With increasing duration of salinity exposure, gene transcript levels were typically upregulated in seawater samples compared to freshwater samples for both non-lethal and lethal tissues. The targeted genes for both non-lethal and lethal tissues were significantly and positively correlated across time points. Our findings support the use of non-lethal tissue sampling to improve Chinook salmon hatchery rearing, inform hatchery release timing, and facilitate future field application for the conservation of wild stocks.

genomics↗

bioRxiv2024

Transcriptional profiling provides insights on sublethal thermal stress thresholds in juvenile bull trout

Bull trout (Salvelinus confluentus) inhabit mainly cold-water streams in their Western North American range. Multiple anthropogenic stressors, including climate change, have caused population declines and range reduction, leading to classification of bull trout as threatened. Characterizing how fish respond to increasing temperature can identify key thresholds beyond which fish health is impacted, which is useful for developing species recovery strategies. Juvenile bull trout were acclimated to a range of relevant temperatures (6-21 {degrees}C), after which mRNA transcripts involved in responding to thermal stress were measured using high- throughput qPCR, and their upper thermal tolerance (critical thermal maximum, CTmax) was determined. Beyond 18 {degrees}C appears to be a critical sublethal threshold for bull trout: capacity to increase CTmax through acclimation was lost, growth and survival decreased, and transcriptional data suggest widespread activation of cellular stress and growth suppression. Below 18 {degrees}C, transcriptional data suggest subtler metabolic adjustments in response to acclimation temperature, preceding changes in whole-animal performance. Altogether, these data provide insight into thermal responses in bull trout, and their capacity to cope with climate-change related warming.

physiology↗

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↗

bioRxiv2022

Acute thermal stress elicits interactions between gene expression and alternative splicing in a fish of conservation concern

Transcriptomics provides a mechanistic understanding of an organisms response to environmental challenges such as increasing temperatures, which can provide key insights into the threats posed by thermal challenges associated with urbanization and climate change. Differential gene expression and alternative splicing are two elements of the transcriptomic stress response that may work in tandem, but relatively few studies have investigated these interactions in fishes of conservation concern. We studied the imperilled redside dace (Clinostomus elongatus) as thermal stress is hypothesised to be an important cause of population declines. We tested the hypothesis that gene expression-splicing interactions contribute to the thermal stress response. Wild fish exposed to acute thermal stress were compared with both handling controls and fish sampled directly from a river. Liver tissue was sampled to study the transcriptomic stress response. Thermally stressed fish showed a prominent transcriptional response (estimated with mRNA transcript abundance) related to transcription regulation and responses to unfolded proteins, and prominent alternatively spliced genes related to gene expression regulation and metabolism. One splicing factor, prpf38b, was upregulated in the thermally stressed group compared to the other treatments. This splicing factor may have a role in the Jun/AP-1 cellular stress response, a pathway with wide-ranging and context-dependent effects. Given large gene interaction networks and the context-dependent nature of transcriptional responses, our results highlight the importance of understanding interactions between gene expression and splicing for understanding transcriptomic responses to thermal stress. Our results also reveal transcriptional pathways that can inform conservation breeding, translocation, and reintroduction programs for redside dace and other imperilled species by identifying appropriate source populations. SUMMARY STATEMENTGene expression and alternative splicing interact in response to thermal stress in an imperilled fish, with implications for conservation and mechanisms of thermal tolerance in vertebrate ectotherms.

physiology↗