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Identification of a gene set to evaluate the potential effects of loud sounds from seismic surveys on the ears of fishes: a study with Salmo salar.

ABSTRACT: Functional genomic studies were carried out on the inner ear of Atlantic salmon Salmo salar following exposure to a seismic airgun. Microarray analyses revealed 79 unique transcripts (passing background threshold), with 42 reproducibly up-regulated and 37 reproducibly down-regulated in exposed v. control fish. Regarding the potential effects on cellular energetics and cellular respiration, altered transcripts included those with roles in oxygen transport, the glycolytic pathway, the Krebs cycle and the electron transport chain. Of these, a number of transcripts encoding haemoglobins that are important in oxygen transport were up-regulated and among the most highly expressed. Up-regulation of transcripts encoding nicotinamide riboside kinase 2, which is also important in energy production and linked to nerve cell damage, points to evidence of neuronal damage in the ear following noise exposure. Transcripts related to protein modification or degradation also indicated potential damaging effects of sound on ear tissues. Notable in this regard were transcripts associated with the proteasome-ubiquitin pathway, which is involved in protein degradation, with the transcript encoding ubiquitin family domain-containing protein 1 displaying the highest response to exposure. The differential expression of transcripts observed for some immune responses could potentially be linked to the rupture of cell membranes. Meanwhile, the altered expression of transcripts for cytoskeletal proteins that contribute to the structural integrity of the inner ear could point to repair or regeneration of ear tissues including auditory hair cells. Regarding potential effects on hormones and vitamins, the protein carrier for thyroxine and retinol (vitamin A), namely transthyretin, was altered at the transcript expression level and it has been suggested from studies in mammalian systems that retinoic acid may play a role in the regeneration of damaged hair cells. The microarray experiment identified the transcript encoding growth hormone I as up-regulated by loud sound, supporting previous evidence linking growth hormone to hair cell regeneration in fishes. Quantitative (q) reverse transcription (RT) polymerase chain reaction (qRT-PCR) analyses confirmed dysregulation of some microarray-identified transcripts and in some cases revealed a high level of biological variability in the exposed group. These results support the potential utility of molecular biomarkers to evaluate the effect of seismic surveys on fishes with studies on the ears being placed in a priority category for development of exposure-response relationships. Knowledge of such relationships is necessary for addressing the question of potential size of injury zones.

SUBMITTER: Andrews CD

PROVIDER: S-EPMC4277336 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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Identification of a gene set to evaluate the potential effects of loud sounds from seismic surveys on the ears of fishes: a study with Salmo salar.

Andrews C D CD Payne J F JF Rise M L ML

Journal of fish biology 20140509 6

Functional genomic studies were carried out on the inner ear of Atlantic salmon Salmo salar following exposure to a seismic airgun. Microarray analyses revealed 79 unique transcripts (passing background threshold), with 42 reproducibly up-regulated and 37 reproducibly down-regulated in exposed v. control fish. Regarding the potential effects on cellular energetics and cellular respiration, altered transcripts included those with roles in oxygen transport, the glycolytic pathway, the Krebs cycle ...[more]

PMID: 24814183

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Project description:Considerable interest and controversy has arisen over the potential effects of seismic surveys carried out during exploration for oil and gas deposits. Regarding fish, there is a concern that intense sound sources, such as seismic airguns, may injure their auditory system. In this study, salmonid cDNA microarrays, reciprocal suppression subtractive hybridization (SSH) cDNA libraries and quantitative reverse transcription – polymerase chain reaction (QPCR) were used to identify and study a responsive gene set in the inner ear of Atlantic salmon (Salmo salar) following seismic airgun exposure. Microarray analyses on pooled seismic exposed inner ear RNA versus pooled control inner ear RNA revealed 79 unique transcripts (passing background threshold) that were greater than 1.75-fold differentially-regulated by acoustic stress on at least 3 of the 4 slides in the study (including at least one dye-swap). QPCR analyses of 8 microarray-identified transcripts of interest revealed a significant up-regulation (P<0.05) of transcripts encoding nicotinamide riboside kinase 2 (1.89-fold) and hemoglobin subunit alpha-4 (3.78-fold), and a significant down-regulation (P<0.05) of a transcript encoding C14orf159 protein (1.35-fold). QPCR analyses also confirmed an overall up-regulation of transcripts encoding growth hormone I (7.78-fold), c-type lectin receptor A (2.20-fold) and retinol binding protein I (1.24-fold), however these differences were not considered to be statistically significant (P<0.05) due to the high biological variability in the seismic exposed group for these transcripts of interest. A total of 683 expressed sequence tags (ESTs) generated from SSH cDNA salmon ear libraries enriched for genes responsive to seismic airgun noise have been deposited in the GenBank dbEST. Targeted gene discovery in salmon ear allowed for the identification of novel transcripts, including some with sensory-relevant functional annotations, and represents a significant contribution to salmonid hearing research. Initial results demonstrate that genomics has the potential to greatly enhance our understanding of the impact of seismic airguns on gene and molecular pathways involved in hearing, and provide valuable molecular biomarkers that can act as an early warning sensor to acoustic stress. Juvenile Atlantic salmon (Salmo salar) smolt were obtained from North Water Products Ltd., Daniel’s Harbour, NL and held at ambient seawater temperature, in a flow-through system supplied with air at the Northwest Atlantic Fisheries Centre, St. John’s, NL. Two weeks prior to seismic airgun exposures, fish were divided into two 1m3 cages, one each for control (non-exposed) and exposed groups, in a 15,000L aquarium at ambient seawater temperature (0.2°C). Each cage was placed the same distance from the water intake and airstones were placed next to each cage. Fish were fasted for two days prior to exposure. Sixteen control (non-exposed) fish from one cage were sampled prior to seismic activity. Immediately following sampling of control fish, seventeen fish in the remaining cage were placed 2m from a 10in3 Texas Instruments airgun. Fish were subjected to 50 exposures, 1 exposure every 10 seconds, at an average sound pressure level of 204 dB peak-to-peak relative to 1µPa; considered to be a worse case scenario within a few hundred meters of a survey vessel. Seventeen seismic exposed fish were sampled 16 h following exposure. The only aquarium available that was suitable for seismic airgun exposures was not designed to have a regulated photoperiod. For this reason the fish were held under a constant daylight regime. Fish were collected by dip-net and euthanized by severing the spinal cord. The inner ears from each salmon were removed, placed immediately in RNase-free 2 ml tubes, and then flash frozen in liquid nitrogen. RNA isolated from the right inner ear of the 12 seismic exposed and 12 control individuals that gave the highest total RNA yields were used to generate 2 mRNA pools (a “seismic” pool and a “control” pool). Each sample contributed 4.0 µg column purified total RNA to each pool. Comparisons were made for the seismic exposed mRNA pool compared to the control (non-exposed) mRNA pool using the consortium for Genomic Research on All Salmonids Project (cGRASP) 16K (salmonid) cDNA array and the 3DNA Array 900 Detection Kit and instructions (Genisphere). Technical quadruplicate slides including 2 dye-swaps were run for the comparison. Slide GG003_011: Cy5-labeled control ear, Cy3-labeled seismic Slide GG003_012: Cy5-labeled control ear, Cy3-labeled seismic Slide GG003_013: Cy3-labeled control ear, Cy5-labeled seismic Slide GG003_014: Cy3-labeled control ear, Cy5-labeled seismic

Dataset Information

Identification of a gene set to evaluate the potential effects of loud sounds from seismic surveys on the ears of fishes: a study with Salmo salar.

Publications

Identification of a gene set to evaluate the potential effects of loud sounds from seismic surveys on the ears of fishes: a study with Salmo salar.

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