Metabolomic-based analysis reveals bile acid-mediated ovarian failure induced by low temperature in zebrafish.

As ectotherms, fish are highly sensitive to temperature fluctuations, which can profoundly impact their reproductive cycles. In this study, we investigated the fertility and histological characteristics of zebrafish ( Danio rerio) ovaries exposed to a temperature gradient ranging from the thermopreferendum temperature of the species, 27°C, to lower temperatures of 22°C, 20°C, and 13°C over a period of two weeks. Comparative metabolomic (six biological replicates for each temperature) and transcriptomic (four biological replicates for each temperature) analyses were conducted under the four temperature conditions. Results indicated that lower temperatures inhibited oocyte development and differential metabolites were involved in steroid hormone production, antioxidant function, and lipid and protein catabolism. Disrupted reproductive hormones, increased proteolysis, and lipid degradation significantly impeded oocyte development and egg maturation. Notably, a significant increase in bile acid content was noted in the ovaries of the cold-treated fish, indicating that bile acids play a critical role in ovarian failure. Overall, these findings provide valuable insights into the mechanisms governing the reproductive response of fish to cold stress.

Tissue-specific temperature dependence of RNA editing levels in zebrafish.

BACKGROUND: RNA editing by adenosine deaminase acting on RNA (ADAR) occurs in all metazoans and fulfils several functions. Here, we examined effects of acclimation temperature (27 °C, 18 °C,13 °C) on editing patterns in six tissues of zebrafish (Danio rerio). RESULTS: Sites and total amounts of editing differed among tissues. Brain showed the highest levels, followed by gill and skin. In these highly edited tissues, decreases in temperatures led to large increases in total amounts of editing and changes in specific edited sites. Gene ontology analysis showed both similarities (e.g., endoplasmic reticulum stress response) and differences in editing among tissues. The majority of edited sites were in transcripts of transposable elements and the 3'UTR regions of protein coding genes. By experimental validation, translation efficiency was directly related to extent of editing of the 3'UTR region of an mRNA. CONCLUSIONS: RNA editing increases 3'UTR polymorphism and affects efficiency of translation. Such editing may lead to temperature-adaptive changes in the proteome through altering relative amounts of synthesis of different proteins.