Spatiotemporally specific expression of miR-203 in the skin. (a) At E13.5, miR-203 is absent from the single layer of multipotent skin stem cells. (b) When the epidermis begins to stratify and gives rise to differentiated suprabasal layers at E15.5, miR-203 is specifically induced in the differentiated layers. (c) At E17.5, miR-203 starts to express in differentiated cells located in the hair germ (hg), whereas it continues to expand in the suprabasal epidermis. (d) With the progressive maturation of the hair follicle, the expression of miR-203 in differentiated lineages of the hair follicle becomes clearly visible at P0.5. (e) At P6.5, miR-203 is highly expressed in all differentiated skin lineages that exit the cell cycle and stop dividing while absent from all stem/progenitor skin lineages that either have proliferative potential, for example, stem cells, or actively divide, for example, matrix cells