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Background: Well-balanced interactions between gut microbiota and the immune system are essential to prevent chronic intestinal inflammation, as observed in inflammatory bowel diseases (IBD). Toll-like receptor 4 (TLR4) functions as a sensor mediating the crosstalk between the intestinal commensal microbiome and host immunity, but the influence of TLR4 on the shaping of intestinal microbiota and immune responses during colon inflammation remains poorly characterized. We investigated whether the different susceptibilities to colitis between wild-type (WT) and TLR4−/− mice were gut microbiota-dependent and aimed to identify the potential immunity modulation mechanism. Methods: We performed antibiotic depletion of the microbiota, cohousing experiments, and faecal microbiota transplantation (FMT) in WT and TLR4−/− mice to assess the influence of TLR4 on intestinal microbial ecology. 16S rRNA sequencing was performed to dissect microbial discrepancies, and dysbiosis-associated immune perturbation was investigated by flow cytometry. Akkermansia muciniphila (A. muciniphila)-mediated immune modulation was confirmed through the T-cell transfer colitis model and bone marrow chimaera construction. Results: TLR4−/− mice experienced enhanced susceptibility to DSS-induced colitis. 16S rRNA sequencing showed notable discrepancy in the gut microbiota between WT and TLR4−/− mice. In particular, A. muciniphila contributed most to distinguishing the two groups. The T-cell transfer colitis model and bone marrow transplantation (BMT) consistently demonstrated that A. muciniphila ameliorated colitis by upregulating RORγt+ Treg cell-mediated immune responses. Mucosal biopsies from human manifested parallel outcomes with colon tissue from WT mice, as evidenced by the positive correlation between TLR4 expression and intestinal A. muciniphila colonization during homeostasis. Conclusions: Our results demonstrate a novel protective role of TLR4 against intestinal inflammation, wherein it can modulate A. muciniphila-associated immune responses. These findings provide a new perspective on host-commensal symbiosis, which may be beneficial for developing potential therapeutic strategies. CehHU1DpMuC43wfy6GXbFM Video abstract. [ABSTRACT FROM AUTHOR]

Background: Genesis of novel gene regulatory modules is largely responsible for morphological and functional evolution. De novo generation of novel cis-regulatory elements (CREs) is much rarer than genomic events that alter existing CREs such as transposition, promoter switching or co-option. Only one case of de novo generation has been reported to date, in fish and without involvement of phenotype alteration. Yet, this event likely occurs in other animals and helps drive genetic/phenotypic variation., Results: Using a porcine model of spontaneous hearing loss not previously characterized we performed gene mapping and mutation screening to determine the genetic foundation of the phenotype. We identified a mutation in the non-regulatory region of the melanocyte-specific promoter of microphthalmia-associated transcription factor (MITF) gene that generated a novel silencer. The consequent elimination of expression of the MITF-M isoform led to early degeneration of the intermediate cells of the cochlear stria vascularis and profound hearing loss, as well as depigmentation, all of which resemble the typical phenotype of Waardenburg syndrome in humans. The mutation exclusively affected MITF-M and no other isoforms. The essential function of Mitf-m in hearing development was further validated using a knock-out mouse model., Conclusions: Elimination of the MITF-M isoform alone is sufficient to cause deafness and depigmentation. To our knowledge, this study provides the first evidence of a de novo CRE in mammals that produces a systemic functional effect.

Background: The impact of miRNA differential expression on the auditory epithelium stem cell development in postnatal rats is not clear. The present study was designed to analyze miRNA expression in the organ of Corti of neonatal and adult rats., Methods: The cochleae of newborn (P0) and adult (P30) Sprague-Dawley rats were dissected in cold PBS to collect the sensory epithelia. Small RNAs were extracted using the mirVana RNA Isolation kit. Then, miRNA expression profiling was performed with RNAs from three newborns and three adult rats utilizing the TaqMan Array Rodent MicroRNA Panel., Results: Eighteen miRNAs were found be differentially expressed, 16 were unregulated in mature cochleae with the fold changes ranging from 17 to 600 folds. The expression levels of two miRNAs were reduced in the mature rat cochleae. GO analysis and signaling pathway analysis revealed the potential involvement of the miRNAs in the regulation of Wnt and TGF-β signaling pathways in hair cell development., Conclusions: Our results provided novel insights into the functional significance of miRNAs in the basilar membrane cells development, and revealed the potential importance of miRNAs in the hair cell by regulation of Wnt and TGF-β signaling.