The miR-424(322)/503 gene cluster regulates pro- vs anti-inflammatory skin DC subset differentiation by modulating TGF-βsignaling

TGF-β family ligands are key regulators of dendritic cell (DC) differentiation and activation. Epidermal Langerhans cells (LCs) require TGF-β family signaling for their differentiation and canonical TGF-β1 signaling secures a non-activated LC state. LCs reportedly control skin inflammation and are replenished from peripheral blood monocytes, which also give rise to pro-inflammatory monocyte-derived DCs (moDCs). By studying mechanisms in inflammation, we previously screened LCs vs moDCs for differentially expressed miRNAs. miR-424/503 was the most strongly inversely regulated (moDCs > LCs). We found that miR-424/503 is induced during moDC differentiation and promotes moDC differentiation in human and mouse. Inversely, forced repression of miR-424 during moDC differentiation facilitated TGF-β1-dependent LC differentiation. Mechanistically, miR-424/503 deficiency in monocyte/DC precursors leads to the induction of TGF-β1-response genes critical for LC differentiation. Therefore, the miR-424/503 gene cluster plays a decisive role in anti-inflammatory LC vs pro-inflammatory moDC differentiation from monocytes. To decipher the role of miR-424(322/503), we performed RNA-seq for the bone marrow of WT and miR-424(322/503) KO mice at day 0 and day 2 after GM-CSF stimulation.