Deletion of Dicer in the epidermis induces DNA damage.

<p><b>A</b>) Representative hematoxylin and eosin staining of skin sections of 7-8 month old K5-Cre+ control mice, and of 7-8 month old Dicer-ablated mice with (Dicer^Δ/Δ) or without functional p53 (Dicer^Δ/Δ, p53^Δ/Δ). <b>B</b>) Phospho-H2A.X staining of representative skin samples reveals DNA damage in <i>Dicer</i>-ablated skin. <b>C</b>) Staining of sections for phospho-ATM indicates activation of DNA damage signaling (ATM auto-phosphorylation) specifically in <i>Dicer</i>-ablated skin, regardless of p53 status. Scale bars equal 100 microns. <b>D</b>) Quantification of DNA damage levels in the epidermis of Dicer-ablated mice. Average percentage of phospho-H2A.X positive nuclei shown (bars), with standard deviation. Little phospho-H2A.X staining was observed in the epidermis of wildtype mice or of K5-Cre control mice (white bars), whereas increased staining was seen in Dicer-ablated skin (gray bar) and in Dicer, p53 co-ablated skin (black bar) relative to controls. Asterisks indicate p values<0.01 between control and Dicer-ablated skin or control and Dicer, p53 co-ablated skin.