Differential cardiac microRNA expression in anoxic Trachemys scripta elegans turtles

Red-eared slider turtles (Trachemys scripta elegans) possess exceptional tolerance to prolonged periods of anoxia, surviving seasonally in oxygen-deprived environments without apparent cardiac damage. This resilience is supported by deep metabolic suppression and transcriptional reprogramming, but the contribution of microRNA in post-transcriptional gene regulatory control remains poorly understood. Here, we employed small RNA sequencing to profile cardiac miRNA expression under normoxic and anoxic conditions. Differential expression analysis of 26 human-conserved miRNAs reveal upward trends in miR-1973 (p = 0.003) and miR-6747-5p (p = 0.011) in response to 20 h of anoxia at 5 °C. Predicted gene set enrichment analysis suggest roles for miRNA in diverse protein post-translational modification, cytoskeletal remodeling and metabolic adaptation through suppression of the ribosome and oxygen-dependent activities. Separately, 35 non-human miRNAs mapped to Chrysemys picta turtles revealed an additional four (cpi-miR-2188-5p, cpi-miR-15b-5p, cpi-miR-551-5p, cpi-miR-1805-3p) that were anoxia-responsive (|FC| > 1.5, FDR-adjusted p < 0.05). These results provide evidence that miRNAs may contribute to cardiac plasticity in T.s. elegans by modifying the cellular phenotype and reducing energy expenditure during anoxia. Our study proposes novel insights into the post-transcriptional control of vertebrate anoxia tolerance and highlights potential regulatory motifs relevant to ischemia-reperfusion medicine.