Identification of miR-141 as a Regulator of Homeostasis

MicroRNAs, small endogenous noncoding RNAs, are involved in the regulation of epidermal homeostasis. Among them, miR-203 was the most described and expressed in human epidermis, promoting keratinocyte (KC) differentiation by repressing genes involved in proliferation. To identify other microRNAs involved in this process, the miRNomes of normal human KCs cultured in monolayer (2-dimensional) or in 3-dimensional reconstructed skin were compared. Besides miR-203, miR-141 was one of the most expressed microRNAs in 3-dimensional culture and was overexpressed in 3-dimensional versus 2-dimensional condition, that is, during KC differentiation. Functional experiments revealed that, mostly expressed in the basal layer, miR-141 decreased KC proliferation and clonogenicity while promoting differentiation. Target prediction algorithm coupled with transcriptomic data of KCs overexpressing miR-141 as well as 30 untranslated region luciferase assays highlighted CCND2 mRNA as a direct target of miR-141, leading to its downregulation by miR-141 overexpression. Finally, CCND2 silencing decreased KC proliferation and induced differentiation, revealing that miR-141 action was mediated by CCND2. MiR-141 features were also compared with those of miR-203 in parallel experiments. Although miR-141 displayed functions similar to those of miR-203, it exhibited different localization and targets, suggesting a joint participation of miR-141 and miR-203 in engaging and maintaining KC toward differentiation, respectively.