KLF4 coordinates corneal epithelial apicobasal polarity and plane of cell division, and is downregulated in ocular surface squamous neoplasia

Apicobasal polarity (ABP) is an important feature of many epithelial cells, including those in the stratified squamous corneal epithelium (CE). Previously, we demonstrated that KLF4 promotes CE homeostasis by suppressing epithelial-mesenchymal transition (EMT) and TGF-{beta} signaling. As dysregulation of TGF-{beta} signaling affects ABP, we investigated the role of KLF4 in regulating cell polarity and plane of division by spatiotemporally regulated ablation of Klf4 in adult ternary transgenic Klf4{Delta}/{Delta}CE (Klf4LoxP/LoxP/Krt12rtTA/rtTA/Tet-O-Cre) mouse CE. Klf4{Delta}/{Delta}CE cells displayed decreased expression and mis-localization of apical polarity markers Pals1 and Crumbs1, apicolateral Par3, and basolateral Scribble. Cdc42 was upregulated, while Rac and Rho were mis-localized in the Klf4{Delta}/{Delta}CE cytoplasm unlike their cortical expression in the control. Phalloidin staining revealed disrupted actin cytoskeleton in the Klf4{Delta}/{Delta}CE cells. Survivin and phospho-histone-H3 immunostaining revealed a tilt in the plane of cell division favoring symmetrical divisions with vertical axis in the Klf4{Delta}/{Delta}CE compared with predominantly asymmetrical divisions with horizontal axis in the control. Human ocular surface squamous neoplasia (OSSN) tissues displayed signs of EMT and loss of ABP markers PAR3, PALS1 and SCRIB, coupled with downregulation of KLF4. By demonstrating that Klf4 ablation affects CE expression of ABP markers and Rho family GTPases, cytoskeletal actin organization and the plane of cell division, and that KLF4 is downregulated in OSSN tissues that display EMT and lack ABP, these results elucidate the key integrative role of KLF4 in coordinating CE cell polarity and plane of division, loss of which results in OSSN.