oar-mir-21: Oar-mir-21 is a known miRNA that has been validated in various studies [PMC4657999]. It has been found to be differentially expressed in sheep-related diseases and is worth further investigation in the context of seasonal reproduction [PMC9464909]. Oar-mir-21 has also been identified as a target of other miRNAs in competitive endogenous RNA networks [PMC9464909]. Additionally, it has been reported to be highly expressed in ovine ovarian follicles and is differentially regulated between different photoperiods [PMC4287553] [PMC9428447]. Oar-mir-21, along with other miRNAs, has been found to be unique to peripheral blood mononuclear cells (PBMC) and not stromal cells, suggesting its involvement in immune mechanisms [PMC6893480]. It is highly expressed in the lungs of sheep with lesions and may serve as an indicator of lesion severity or a potential therapeutic target for lung diseases [PMC6339376]. Oar-mir-21, along with other miRNAs, may also have implications for host-virus interactions [PMC6339376] [PMC9344810]. The expression of oar-mir-21 has been validated using qPCR and its upregulation confirmed in diseased animals compared to seronegative animals [PMC6339376]. It is one of the most abundant differentially expressed miRNAs and primarily immune-related among sheep miRNAs [PMC6339376] [PMC7070426]. Furthermore, oar-mir-21 has been shown to downregulate reporter fluorescence through interactions with specific 3' UTR sites on various genes such as KLF3, CNKSR2, and TNPO1[ PMC6599667].