PIWI-interacting RNA (piRNA) HAAPIR directly interacts with NAT10 and promotes CM apoptosis by enhancing ac4C acetylation of transcription factor EC (TFEC), which results in deteriorated cardiac function in MI.311 m6A levels increase with downregulated FTO expression in mammalian HF and CMs suffering from hypoxia, rather than cardiac fibroblasts (CFs) or ECs.312 FTO overexpression improves sarcomere contraction by regulating intracellular Ca2+ and cardiac function after MI, due to FTO-mediated demethylation of ATP2A2 mRNA (coding SERCA2a protein) in response to increased ATP2A2 mRNA levels. Here, ATP2A2 is linked to hydrops fetalis.