Novel transcriptome assembly and comparative toxicity pathway analysis in mahi-mahi (Coryphaena hippurus) embryos and larvae exposed to Deepwater Horizon oil

Abstract

The impacts of Deepwater Horizon (DWH) oil on morphology and function during embryonic development have been documented for a number of fish species, including the economically and ecologically important pelagic species, mahi-mahi (Coryphaena hippurus). However, further investigations on molecular events and pathways responsible for developmental toxicity have been largely restricted due to the limited molecular data available for this species. We sought to establish the de novo transcriptomic database from the embryos and larvae of mahi-mahi exposed to water accommodated fractions (HEWAFs) of two DWH oil types (weathered and source oil), in an effort to advance our understanding of the molecular aspects involved during specific toxicity responses. By high throughput sequencing (HTS), we obtained the first de novo transcriptome of mahi-mahi, with 60,842 assembled transcripts and 30,518 BLAST hits. Among them, 2,345 genes were significantly regulated in 96hpf larvae after exposure to weathered oil. With comparative analysis to a reference-transcriptome-guided approach on gene ontology and tox-pathways, we confirmed the novel approach effective for exploring tox-pathways in non-model species, and also identified a list of co-expressed genes as potential biomarkers which will provide information for the construction of an Adverse Outcome Pathway which could be useful in Ecological Risk Assessments.

Exposure to Oil and Hypoxia Results in Alterations of Immune Transcriptional Patterns in Developing Sheepshead Minnows (Cyprinodon variegatus)

“…The mahi mahi study noted activation of these same three pathways in both life stage transitions 19 . Interestingly, magnitude and directionality of immune-related transcriptional responses appear to depend on length of oil exposure and type of oil: most immune-related pathways were activated at 96 hours of exposure to slick oil in mahi mahi, but were mostly unaffected at 96 hours of exposure to source oil 20 . At 48 hours of exposure to source of slick oil (the same amount of time as our exposure duration), most immune pathways were suppressed or unchanged in mahi mahi, and at 24 hours of exposure to source or slick oil, no immune pathways were altered 20 .…”

“…We then performed RNAseq and bioinformatic analyses to determine differentially expressed transcripts and pathways between treatment groups and age stages, with a specific focus on immune-related genes and pathways. Previous research in developing fish has found that exposure to oil does significantly impact some immune-related pathways [19][20][21] . Therefore, we wanted to examine how the effects of these stressors change transcriptional patterns as the developing fish undergo two significant transitions: between the embryonic and post-hatch life stages, and between the post-hatch and post-larval life stages.…”

Untangling mechanisms of crude oil toxicity: linking gene expression, morphology and PAHs at two developmental stages in a cold-water fish

“…Recently, a study linked oil-induced changes in lipid composition and dynamics to reduced growth and survival in polar cod (Boreogadus saida) (Laurel et al, 2019). Consistently, impacts on lipid metabolism pathways have been reported in several RNAseq studies (Sørhus et al, 2017;Xu et al, 2017). Several gene expression studies have started to unravel initiating events and key events of adverse outcome pathways of crude oil (Laurel et al, 2019;Lie et al, 2019;McGruer et al, 2019;Sørhus et al, 2017), but there are still knowledge gaps in understanding the underlying mechanisms of crude oil toxicity.…”

“…A circulation-and time-independent expression of bmp10 suggests a direct effect of crude oil on calcium homeostasis. Several signaling pathways linked to cardiac development and proliferation are impacted by the complexity of crude oil exposure, including calciumregulated pathways (Sørhus et al, 2017;Xu et al, 2017), AhR (Yin et al, 2008) and retinoic acid (Lie et al, 2019)-dependent pathways. Disruption of intracellular calcium levels has been shown to reduce cardiomyocyte proliferation leading to smaller ventricles (Ebert et al, 2005;Rottbauer et al, 2001), suggesting that ventricular proliferation is calcium controlled.…”

Transcriptomics in aquaculture: current status and applications

“…Xu et al . () analysed genes responsible for deep‐water horizon oil toxicity in mahi‐mahi ( Coryphaena hippurus ). This study described the genes causing toxic effect such as liver proliferation, cholesterol biosynthesis, cardiac hypertrophy, and renal necrosis/apoptosis.…”