mmu-mir-667: Mmu-mir-667 is a mature miRNA derived from the mmu-mir-667 precursor miRNA, which is relatively unique in the mouse genome/transcriptome [PMC6366741]. It is one of the miRNAs located on chromosome 12, specifically in a clustered region with mmu-mir-679 [PMC6366741]. Mmu-mir-667 is the only candidate in this region whose targets are predicted to have a significant association with P < 0.001 [PMC4579042]. It does not have targets in Comt mRNA, which is downregulated by other miRNAs such as mmu-miR-3470a/b [PMC4579042]. Lentiviral injections of mmu-miR-3470a, mmu-miR-3470b, and mmu-mir-667 have been shown to increase hypersensitivity during tonic inflammatory pain states in mice [PMC4579042]. The expression of mmu-mir-667 and other related miRNAs has been estimated across various mouse tissues and cells using RNA-seq data sets [PMC4579042]. Lentiviral vectors were used to subcutaneously inject these miRNAs into the foot plantar surface to confirm their modulation of pain responses in vivo [PMC4579042]. In vitro experiments have shown that both mRNA and enzymatic activity of murine ancestral Comt can be downregulated by mmu-mir-667, mmu-miR-3470a, or mmu-miR-3470b miRNAs. Mmu-mir-667 has been found to downregulate COMT protein level more robustly than mRNA level, suggesting its role in controlling translational efficiency as well as mRNA stability [PMC4579042].