Fig. 3. Increase in cell proliferation accompanies utricle formation. (A) Immunohistochemical detection of PCNA (proliferating cell nuclear antigen) in sagittal sections from backskin of P16 mice. Arrowheads indicate PCNA-positive cells in interfollicular epidermis, infundibulum (in wild type, +/+) and utricle (in Hr^-/-, -/-). (B) Proliferating cells in utricle express K14. Immunofluorescent detection of BrdU (red) and keratin 14 (green) in sagittal skin sections from P20 mice. White arrowheads indicate BrdU-positive cells. DAPI (blue), nuclear marker. (C) Utricle epithelium does not express keratin 16 (K16), a marker of abnormal epidermal differentiation. Immunohistochemical detection of K16 in sagittal sections from backskin at P20; K16 expression is detected in club hair sheath (chs). Arrowheads in C indicate infundibulum. -/-, Hr^-/-; +/+, wild type. Scale bar: 50 µm.