mmu-mir-665: Mmu-mir-665 is a microRNA located on chromosome 12, specifically in a cluster with mmu-mir-431, mmu-mir-679, and mmu-mir-667 [PMC6366741]. It has been shown to regulate the expression of the Abcc3 gene in response to colonization [PMC6599659]. Comparative profiling of miRNA expression in conventional and germ-free mice revealed that mmu-mir-665 is dysregulated during colonization and directly targets the 3'-UTR of Abcc3 mRNA, leading to down-regulation of Abcc3 expression [PMC3224226] [PMC3084815]. Luciferase assays and GFP production assays confirmed the repressive effect of mmu-mir-665 on Abcc3 expression [PMC3084815]. In the colon, Abcc3 was identified as a potential target gene for mmu-mir-665, while no overlapping gene was found for the ileum [PMC3084815]. It is suggested that gut microbiota may upregulate Abcc3 expression by down-regulating mmu-mir-665 [PMC3084815]. In vitro experiments demonstrated that upregulation of Abcc3 during colonization was associated with downregulation of mmu-mir-665 [PMC9468484]. These findings suggest that miRNA-mediated regulation by mmu-mir-665 may play a role in gut microbiota-induced changes in host gene expression.