Microrna Expression in Aurelia aurita Metamorphosis

In animal taxa and jellyfish, the same genome encodes for the dif-ferent phenotypes that characterize life stages that follow each other during ontogeny. This situation underscores the existence of profound regulation of genomic information at the epigenetic level. MicroRNAs are fundamental epigenetic regulators. The aim of this study is to evaluate the role of microRNA regulation during jellyfish metamorphosis and to explore the existence of evolutionarily conserved microRNAs.

Specimens belonging to the 4-metamorphosis stages of A. aurita (polyps, ephyra, young, and adult jellyfish) were bred and collected. The expression of 2,549 miRNAs for each stage was tested using microarray technology. The comparison of microRNA expres-sion for each phase was performed using line plot analysis and Principal Component Anal-ysis of variance (PCA), while the identification of microRNA clusters was performed via volcano plot analysis.

A remarkable number of A. aurita miRNAs specifically hybridize with a human miRNA library. Each metamorphosis stage is characterized by a different level of expression of miRNAs: 1) Polyp vs. Ephyra stage: 128 upregulated, 2 downregulated; 2) Ephyra vs. Young stage: 2 upregulated, 135 downregulated; 3) Young vs. Adult stage: 69 upregulated, 6 downregulated. Specific functions inferred from known activities of corresponding miR-NAs in higher animals (PubMed database) appear to be coherent with the correlated exper-imental model.

Present results reveal that microRNAs with human homologs undergo specific expression changes throughout Aurelia aurita metamorphosis. This observation reinforces the hypothesis of a shared evolutionary origin of certain miRNA families between Cnidaria and Bilateria. The dynamic and stage-specific regulation pattern observed suggests that miR-NAs play a key role in orchestrating the complex transitions involved in jellyfish develop-ment. These findings point to a broader conservation of epigenetic mechanisms, such as miRNA-mediated gene silencing, which may have emerged early in metazoan evolution and contributed to the regulation of cell differentiation and phenotype modulation.

The present study highlights the importance of Aurelia aurita as a model for investigating miRNA-driven epigenetic regulation in non-bilaterian animals. The identifica-tion of human-homologous miRNAs provides novel insights into the evolutionary stability of the epigenetic machinery and suggests conserved regulatory functions across distant taxa. Although limited by the use of a human-based microarray platform, the data presented here lay a solid foundation for future studies employing sequencing and functional assays to fur-ther explore the role of miRNAs in cnidarian development and evolution.