Project description:The goal of this study was to gain a better understanding of the genetic background of gonadal maturation of the European eel and to use gene expression profiles to identify predictive markers for broodstock selection that can be measured in blood samples. Three-year-old farmed silver female European eels were injected with 20 mg salmon pituitary extract (SPE) once per week and sampled after 4 weekly hormone injections. Four responders (gonadosomatic index > 1.5) and two non-responders (gonadosomatic index < 1.0) were selected for Illumina RNAseq analysis to identify early markers of responsiveness to gonadotropin treatment. Deep-sequencing transcriptome analysis of ovarian samples derived from four responsive and two non-responsive eels after four weekly injections with gonadotropins.
Project description:The goal of this study was to gain a better understanding of the genetic background of gonadal maturation of the European eel and to use gene expression profiles to identify predictive markers for broodstock selection that can be measured in blood samples. Three-year-old farmed silver female European eels were injected with 20 mg salmon pituitary extract (SPE) once per week and sampled after 4 weekly hormone injections. Four responders (gonadosomatic index > 1.5) and two non-responders (gonadosomatic index < 1.0) were selected for Illumina RNAseq analysis to identify early markers of responsiveness to gonadotropin treatment.
Project description:Since the early 1980s, the population of European eels (Anguilla anguilla) has dramatically declined. Nowadays, the European eel is listed on the red list of threatened species (IUCN Red List) and is considered as critically endangered of extinction. Pollution is one of the explanations of the collapse of this species. Among their possible effects, pollutants gradually accumulated in eels during their somatic growth phase (yellow eel stage) would be remobilized during their reproductive migration leading to potential toxic events in gonads. The aim of this study was to investigate the potential effect of pollution on the gonad development of wild female silver eels. Female silver eels from two sites with differing contamination levels were artificially matured. Transcriptomic analyses by means of a 1000 candidate gene cDNA microarray were performed on gonads after 11 weeks of maturation. The results showed that the transcription levels of several genes that were associated to the gonadosomatic index (GSI) were involved in mitotic cell division but also in spermatogenesis. Genes associated to pollution were mainly involved in the mechanisms of protection against oxidative stress, in DNA repair, in the purinergic signaling pathway and in steroidogenesis, suggesting an impairment of gonad development in eels from the polluted site. This was in agreement with the fact that eels from the reference site showed a higher gonad growth in comparison to contaminated fish.
Project description:Japanese eel (Anguilla japonica) is a migratory fish with high economic value. The gonads of eels cultured in captivity do not mature naturally, and under artificial ripening, their hypothalamic-pituitary-gonadal axis is activated and the maturation coefficient of the gonads is significantly increased. Previous studies on eel breeding have focused on reproductive physiological processes, with limited insight into the molecular mechanisms in the pituitary gland that influence ovarian development. To address these limitations, we used pituitary tissues of female Japanese eels as samples for Pacbio Iso-Seq and RNA-Seq combining analyses, selecting pre-matured (PP) and after-matured (AP) samples to investigate DEGs and signal pathways regulating gonadal development in the pituitary gland, respectively.
Project description:Background: The Japanese eel (Anguilla japonica) holds significant economic value in East Asia, but limitations in understanding its reproductive biology have hindered advancements in artificial breeding techniques. Previous research has primarily focused on conserved sex differentiation genes, offering limited insights into the broader molecular mechanisms driving gonadal development and sexual dimorphism. To address these limitations, this study aims to investigate key genes and pathways involved in gonadal development through a comprehensive transcriptomic analysis of male and female eel gonads. Results: PacBio Iso-Seq and Illumina RNA-Seq technologies were combined to conduct a full-length transcriptome analysis of male and female Japanese eel gonads at a post-differentiation, pre-maturation stage. A total of 24661 unigenes were identified in ovaries and 15023 in testes, along with genomic regulatory elements such as transcription factors, simple sequence repeats, and long non-coding RNAs. Additionally, 1,210 differentially expressed genes were detected. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed significant pathways involved in cell cycle regulation, metabolic processes, apoptosis, and hormone activity. Notably, several reproductive-related genes, including bambi, ccnb1, cdc20, gdf9, prlh, ccdc39, chrebp, tspo, syce3, and ngb, demonstrated significant dimorphic expression in eel gonads. Conclusions: This study provides valuable insights into the molecular mechanisms of gonadal differentiation and sexual dimorphism in Japanese eels. The findings expand the genetic resources available for the eel breeding industry and could facilitate the development of improved artificial breeding techniques focused on reproductive development.
Project description:Our main objectives were: 1) to test whether the caudal fin may be used to detect the effects of pollutant exposure by means of DNA microarray; 2) to test whether the fin may be used to detect the effects of pollutants in wild contaminated fish; 3) to investigate the mechanisms of toxicity for Cd metal. Detecting and unraveling specific effects of contaminants in a multi-stress field context remain a major challenge in ecotoxicology. The aim of this study was to apply a previously developed DNA microarray comprising 1000 candidate genes on caudal fin clips in order to assess the usefulness of a non-invasive method in ecotoxicogenomic studies in the European eel. Fin gene expression patterns of eels exposed in laboratory to Cd or a PCBs mixture were compared to test whether fin clips may be used to detect effects of these contaminants. Then, gene transcription profiles of wild fish from 3 sampling sites with differing contamination levels were compared to experimental exposures to test whether fin could detect and unravel the in situ effects of these contaminants. Also, transcriptomic profiles from liver and caudal fin of eels experimentally exposed to Cd were compared to test whether fins may be used to investigate the toxicity mechanisms of this metal. Our results showed distinct fin transcription profiles in response to Cd or PCBs exposure. In addition, the transcription profiles of eels from the most contaminated site clustered with the laboratory-exposed fish. Finally, gene transcription patterns from caudal fin and liver in Cd-exposed eels showed significant differences between the two organs and only 16 common genes were identified. Many of these genes were found to be involved in tissue development and in epigenetic mechanisms. This study thus demonstrates the applicability and usefulness of performing gene transcription assays on non-invasive tissue sampling in order to assess the effect of Cd and PCBs on the transcriptome of fish.
Project description:The goal of this study was to gain a better understanding of the genetic background of gonadal maturation of the European eel and to use gene expression profiles to identify predictive markers for broodstock selection that can be measured in blood samples. To find leads for maturation markers we performed a pilot deep-sequencing transcriptome analysis of ovarian tissue derived from a yellow eel, a prepubertal silver eel and a post-spawning matured eel. Among the best leads were two key players in steroidogenesis, namely pP450c17 and liver receptor homolog-1.
Project description:Detecting the effects of Cd and PCBs by means of a non-invasive transcriptomic approach in laboratory- and wild-contaminated European eels (Anguilla anguilla)
Project description:The goal of this study was to gain a better understanding of the genetic background of gonadal maturation of the European eel and to use gene expression profiles to identify predictive markers for broodstock selection that can be measured in blood samples. To find leads for maturation markers we performed a pilot deep-sequencing transcriptome analysis of ovarian tissue derived from a yellow eel, a prepubertal silver eel and a post-spawning matured eel. Among the best leads were two key players in steroidogenesis, namely pP450c17 and liver receptor homolog-1. Pilot deep-sequencing transcriptome analysis of ovary from a yellow, a prepubertal silver and a post-spawning matured eel