Project description:The Atlantic killifish (Fundulus heteroclitus) is an ideal model species to study physiological and toxicological adaptations to stressors. Killifish inhabiting the PCB-contaminated Superfund site in New Bedford Harbor, MA (NBH) have evolved resistance to toxicity and activation of the aryl hydrocarbon receptor (AHR) signaling pathway after exposure to PCBs and other AHR agonists. Until recently, a lack of genomic information has limited efforts to understand the molecular mechanisms underlying environmental adaptation to stressors. The advent of high throughput sequencing has facilitated an unbiased assessment of coding as well as non-coding RNAs in any species of interest. Among non-coding RNAs, microRNAs (miRNAs) are important regulators of gene expression and play crucial roles in development and physiology. The objective of this study is to catalog the miRNAs in killifish and determine their expression patterns in the embryos from contaminated (NBH) and pristine (Scorton Creek, MA (SC)) sites. Embryos from NBH and SC were collected daily from 1 to 15 days post-fertilization and RNA from pooled samples from each site was sequenced using SOLiD sequencing. We obtained 7.5 and 11 million raw reads from pooled SC and NBH samples, respectively. Analysis of the sequencing data identified 216 conserved mature miRNA sequences that are expressed during development. Using the draft killifish genome, we retrieved the miRNA precursor sequences. Based on the capacity of these putative precursor sequences to form the characteristic hairpin loop (assessed using RNAfold), we identified 197 conserved miRNA sequences in the genome.
Project description:Subspecies of the Atlantic killifish, Fundulus heteroclitus, differ in their maximum thermal tolerance. To determine whether there is a link between the heat shock response (HSR) and maximum thermal tolerance, we exposed 20ºC acclimated killifish from these subspecies to a 2hr heat shock at 34ºC and examined gene expression during heat shock and recovery using real time quantitative PCR and a heterologous cDNA microarray designed for salmonid fishes. Keywords: Expression profiling by array
Project description:The Atlantic killifish (Fundulus heteroclitus), native to estuarine areas of the Atlantic coast of the United States, has become a valuable ecotoxicological model due to its ability to acclimate to rapid environmental changes and adapt to polluted habitats. Killifish respond to rapid increases in salinity with an immediate change in gene expression, as well as long-term remodeling of the gills. Arsenic, a major environmental toxicant, was previously shown to inhibit the ability of killifish gill to respond to a rapid increase in salinity. We characterized miRNA expression in killifish gill under salinity acclimation with and without arsenic and identified a small group of highly expressed, well-conserved miRNAs as well as 16 novel miRNAs not yet identified in other organisms.
Project description:Transcriptomic assessment of resistance to effects of an aryl hydrocarbon receptor (AHR) agonist in embryos of Atlantic killifish (Fundulus heteroclitus) from a marine Superfund site
Project description:Subspecies of the Atlantic killifish, Fundulus heteroclitus, differ in their maximum thermal tolerance. To determine whether there is a link between the heat shock response (HSR) and maximum thermal tolerance, we exposed 20ºC acclimated killifish from these subspecies to a 2hr heat shock at 34ºC and examined gene expression during heat shock and recovery using real time quantitative PCR and a heterologous cDNA microarray designed for salmonid fishes. Keywords: Expression profiling by array Microarray analyses were performed on four individual fish per subspecies of killifish (northern and southern) prior to heat shock (control) and after 60 minutes of heat shock, hybridized (one slide per individual) against a common reference RNA pool composed of an equal amount of RNA from all samples in the analysis.
Project description:Hypoxia in coastal waters is an increasing concern, with the frequency of hypoxic events rising because of climate change and human-driven impacts such as eutrophication. The Atlantic killifish (Fundulus heteroclitus), an estuarine species known for its resilience to environmental stressors, provides a valuable model to investigate the physiological, transcriptional, and epigenetic mechanisms underlying adaptation. Some killifish populations, like those in New Bedford Harbor (NBH), Massachusetts, have evolved resistance to dioxin-like polychlorinated biphenyls (PCBs) due to chronic exposure. These populations offer a unique opportunity to investigate how toxicant resistance might influence responses to secondary stressors like hypoxia. The objective of this study is to characterize the impacts of evolved resistance to toxicants on the ability to cope with acute hypoxia. We compared hepatic gene expression and DNA methylation patterns in response to two levels of hypoxia in killifish from NBH and Scorton Creek (SC), a reference population from a relatively pristine environment. We hypothesized that NBH fish would exhibit altered molecular responses to hypoxia due to trade-offs associated with toxicant resistance. Our results revealed significant differences between the two populations. SC fish demonstrated a dose-dependent increase in gene expression in response to hypoxia, while NBH fish exhibited a muted transcriptional response to severe hypoxia, indicating potential impairment in their ability to cope with hypoxic stress. Interestingly, NBH fish showed significant DNA methylation changes in response to hypoxia, while SC fish did not exhibit notable epigenetic alterations. These findings suggest that toxicant-adapted killifish may face trade-offs in their response to additional environmental stressors, with potential consequences for their ability to survive in increasingly hypoxic coastal habitats. Further research is needed to elucidate the functional implications of these epigenetic modifications and their role in adaptive stress responses.
Project description:RNA from PCB-126 exposed 10 days post-fertilization (dpf) embryos were sequenced to characterize the chemical exposure response of killifish from a PCB-resistant population (NBH, New Bedford Harbor, MA, Superfund site) as compared to a reference (SC, Scorton Creek, MA) population. Since the genome sequence was not available, we also performed shot-gun sequencing of RNA from 1-15 dpf embryos sampled every day from both populations to serve as a transcriptome assembly. The results suggest that the NBH fish possess a gene regulatory defect that is not limited to a few target genes. We detected multiple genes that were differentially expressed in these two populations. This study was the first application of pyrosequencing technology to combine transcriptome characterization and gene expression profiling in a marine animal.