Fig. 3.

Ultrastructural defects of Dicer and Dgcr8 cKO skin. (A) Skins from neonatal WT control, Dicer cKO and Dgcr8 cKO mice were fixed and processed for electron microscopy as described. Shown are regions of the epidermis, where a whorl of evaginated hair germ (hg) cells are readily identified by the presence of dermal papilla (DP) cells at the center of the structure. These aberrations in follicle morphogenesis distorted the surrounding epidermis. (Scale bar, 10 μm.) (B) Cells with hair follicle matrix cell (Mx) morphology were present in the evaginating hair germs of Dgcr8 cKO epidermis. These cells frequently contained melanin granules (Mel). Melanocytes are normally never in mouse skin epidermis, and the appearance of melanin within the whorls was an additional hallmark of the evaginating hair germs. (Scale bar, 2 μm.) (C and E) Closed-up pictures of boxed areas in A. Note the presence of hemidesmosomes (Hd) and a loose basal lamina (bl) at the evaginating hair germ-DP border (C) as well as the epidermal-dermal boundary to what appeared to be an underlying DP (E) in the Dgcr8 cKO skin. (Scale bar, 500 nm.) (D) Enriched apoptotic cells (Ap) in hair germs of Dgcr8 cKO skin. (Scale bar, 2 μm.) Additional abbreviations: SC, stratum corneum; Gr, granular layers; Sp, spinous layers; BL, basal epidermal layer; Der, dermis. Dotted lines mark epidermal-dermal boundaries.