Abstract
Purpose :
Apical-basal polarity (ABP) is essential to establish the apical barrier function in many epithelial tissues in the body including the cornea. Previously, we demonstrated that the corneal epithelial (CE) maturation and homeostasis depend on Krüppel-like transcription factor 4 (Klf4) that promotes epithelial identity and suppresses mesenchymal gene expression. We also demonstrated that the mature CE ABP is disrupted in the absence of Klf4. Here we evaluate the expression of ABP-determinants during CE stratification and maturation.
Methods :
We employed 8 mm thick cryosections from postnatal day-8 (PN-8), PN-12, PN-14, and PN-90 wild type mouse eyes to evaluate the expression of ABP determinants Pals1, Par3, Scribble and Cdc42 during CE stratification and maturation by immunofluorescent staining.
Results :
Immunofluorescent staining of sections from mature (PN90) mouse eyes revealed that Klf4 is most intensely expressed in the central CE, and gradually tapered off towards the periphery. ABP markers Pals1, Par3 and Cdc42 were prominently membrane-associated in the central and peripheral mature CE, while faint or no immunostaining was observed in the limbal region or the adjoining conjunctiva. Coincident with the mouse CE stratification, ABP markers Par3, Scribble and Cdc42 were more cortically organized in the PN-12 and PN-14 corneas compared with their diffuse expression in the unstratified PN-8 CE. As the CE matured (PN-90), immunostaining for these markers became more prominently organized in the cortical regions of the CE cells. We also observed that the basal CE has more Yap1 (a nuclear effector of Hippo signaling pathway involved in development, growth, repair, and homeostasis) expression during stratification (PN-12 to PN-14), compared with either the unstratified (PN-8) or fully mature CE (PN-90).
Conclusions :
These results demonstrate dynamic changes in expression of ABP-determinants during CE stratification and their sub-cellular re-organization from being diffusely expressed at PN-8 to being cortically organized at PN-14 and PN-90. Based on these results, we suggest that Klf4 plays a key role in CE stratification by promoting relative enrichment of ABP-determinants in the central CE compared with the limbus or the conjunctiva.
This is a 2021 ARVO Annual Meeting abstract.