miR-210 promotes immune- and suppresses oocyte meiosis-related genes in the zebrafish ovarian cells

microRNA-210 (miRNA), a well-documented miRNA, has been implicated in a myriad of biological processes, including responses to hypoxia, angiogenesis, cell proliferation, and male infertility in humans. However, a comprehensive understanding of its functions in fish requires further investigation. This study pursued to elucidate the downstream effect of dre-miR-210-5p on primary ovarian cell culture in zebrafish (Danio rerio), an animal model. A protocol was settled down by incubations with either an miR-210 mimic or a scrambled miRNA in the isolated ovaries. RNA-sequencing analysis identified ∼6000 differentially expressed target genes revealing that downregulated genes were associated with reproduction-related pathways while immune-related pathways displayed an upregulated pattern. To identify molecular markers, predicted target genes were classified into reproduction and immune cell types. These findings underscore the existence of a profound interplay between the reproductive and immune systems, with miR-210 emerging as a pivotal player in orchestrating transcriptomic alterations within fish ovaries.

Deciphering sex-specific miRNAs as heat-recorders in zebrafish

In the last decade, a plethora of microRNAs (miRNAs) has been reported in a wide variety of physiological processes, including reproduction, in many aquatic organisms. However, miRNAome alterations occurred by environmental cues due to water temperature increment have not yet been elucidated. With the aim to identify epigenetic regulations mediated by miRNAs in the gonads in a climate change scenario, the animal model zebrafish (Danio rerio) were subjected to high temperatures during sex differentiation, a treatment that results in male-skewed sex ratios in the adulthood. Once the fish reached adulthood, gonads were sequenced by high-throughput technologies and a total of 23 and 1 differentially expressed miRNAs in ovaries and testes, respectively, were identified two months after the heat treatment. Most of these heat-recorder miRNAs were involved in human sex-related cancer and about 400 predicted-target genes were obtained, some with reproduction-related functions. Their synteny in the zebrafish genome was, for more than half of the predicted target genes, in the chromosomes 7, 2, 4, 3 and 11 in the ovaries, chromosome 4 being the place where the sex-associated-region (sar) is localized in wild zebrafish. Further, spatial localization in the gonads of two selected heat-recorder miRNAs (miR-122-5p and miR-146-5p) showed exclusive expression in the ovarian germ cells. The present study expands the catalog of sex-specific miRNAs and deciphers, for the first time, thermosensitive miRNAs in the zebrafish gonads that might be used as potential epimarkers to predict environmental past events.