The OE of HBC-specific Pax6-knockout mice. (A–F) Images of hematoxylin and eosin-stained coronal sections from the OE of 6-week-old Pax6flox/flox mice (control; A) and K5-Cre+/−::Pax6flox/flox mice (Pax6-cKO; B). (C–F) NQO1 was stained as a marker for zone 1. (G, H) Pax6 and p63 expression in the OE of control and Pax6-cKO mice. In the OE of control mice, Pax6 was observed in HBCs, GBCs, SUSs, and BG cells (G). The majority of HBCs coexpressed p63 and Pax6 (G, white arrows). In the Pax6-cKO OE, many of the HBCs lacked Pax6 expression (H, yellow arrows), and the percentage of Pax6-positive HBCs was significantly lower in zone 1 compared to control mice (I, left); the percentage of Pax6-positive HBCs was also significantly reduced in zones 2–4 in the Pax6-cKO mice, although to a lesser extent than in zone 1 (I, right). (J) OE thickness did not differ significantly between control and Pax6-cKO mice in zone 1 or zones 2–4. (K) The absolute number of p63-positive HBCs did not differ significantly between control and Pax6-cKO mice in either zone 1 or zones 2–4. The dotted line in (A–H) indicates the basal lamina. Scale bars represent 1,000 μm (A–B), 200 μm (A2, B2, D, F), and 50 μm (G–H). *P<0.05; ***P<0.001. BG, Bowman's gland; GBCs, globose basal cells; LP, lamina propria; OE, olfactory epithelium; NQO1, NAD(P)H dehydrogenase [quinone] 1; SUSs, sustentacular cells. Color images available online at www.liebertpub.com/scd