title: Wnt/β-catenin signaling modulates corneal epithelium stratification via inhibition of Bmp4 during mouse development.
abstract: The development of organs with an epithelial parenchyma relies on reciprocal mesenchymal-epithelial communication. Mouse corneal epithelium stratification is the consequence of a coordinated developmental process based on mesenchymal-epithelial interactions. The molecular mechanism underlying these interactions remains unclear. The Wnt/β-catenin signaling pathway is involved in fundamental aspects of development through the regulation of various growth factors. Here, we show that conditional ablation of either β-catenin (Ctnnb1(cKO)) or co-receptors Lrp5/6 (Lrp5/6(cKO)) in corneal stromal cells results in precocious stratification of the corneal epithelium. By contrast, ectopic expression of a murine Ctnnb1 gain-of-function mutant (Ctnnb1(cGOF)) retards corneal epithelium stratification. We also discovered that Bmp4 is upregulated in the absence of β-catenin in keratocytes, which further triggers ERK1/2 (Mapk3/1) and Smad1/5 phosphorylation and enhances transcription factor p63 (Trp63) expression in mouse corneal basal epithelial cells and in a human corneal epithelial cell line (HTCE). Interestingly, mouse neonates given a subconjunctival BMP4 injection displayed a phenotype resembling that of Ctnnb1(cKO). Conditional ablation of Bmp4 eradicates the phenotype produced in Ctnnb1(cKO) mice. Furthermore, ChIP and promoter-luciferase assays show that β-catenin binds to and suppresses Bmp4 promoter activity. These data support the concept that cross-talk between the Wnt/β-catenin/Bmp4 axis (in the stromal mesenchyme) and Bmp4/p63 signaling (in the epithelium) plays a pivotal role in epithelial stratification during corneal morphogenesis.
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA School of Optometry, Indiana University, Bloomington, IN 47405, USA zhang512@iu.edu liuchia@iu.edu.
authors.forename: Yujin
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Ophthalmology, Chang-Gung Memorial Hospital, Linkou, Taoyuan 333, Taiwan, R.O.C Chang-Gung University College of Medicine, Taoyuan 33302, Taiwan, R.O.C.
authors.forename: Lung-Kun
authors.initials: LK
authors.lastname: Yeh
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA Undergraduate Programs of Biology, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Suohui
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA.
authors.forename: Mindy
authors.initials: M
authors.lastname: Call
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Health Research Institute, National Institute of Advanced Industrial Science and Technology, Takamatsu 761-0395, Japan.
authors.forename: Mayu
authors.initials: M
authors.lastname: Yasunaga
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA.
authors.forename: Winston W-Y
authors.initials: WW
authors.lastname: Kao
authors.affiliation: Edith J. Crawley Vision Research Center, Department of Ophthalmology, University of Cincinnati School of Medicine, Cincinnati, OH 45267, USA School of Optometry, Indiana University, Bloomington, IN 47405, USA zhang512@iu.edu liuchia@iu.edu.
authors.forename: Chia-Yang
authors.initials: CY
authors.lastname: Liu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D055415:Bone Morphogenetic Protein 4 / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D047369:Chromatin Immunoprecipitation; D004318:Doxycycline; D019573:Epithelium, Corneal / Q000196:embryology*; D005453:Fluorescence; D005697:Galactosides; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006652:Histological Techniques; D007150:Immunohistochemistry; D007211:Indoles; D060492:Low Density Lipoprotein Receptor-Related Protein-5 / Q000172:deficiency; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000172:deficiency; D008156:Luciferases; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D009024:Morphogenesis / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism; D060449:Wnt Signaling Pathway / Q000502:physiology*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; C495267:CTNNB1 protein, mouse; D005697:Galactosides; D007211:Indoles; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555483:Lrp5 protein, mouse; C555476:Lrp6 protein, mouse; D010750:Phosphoproteins; D015534:Trans-Activators; C486419:Trp63 protein, mouse; D051176:beta Catenin; D008156:Luciferases; D004318:Doxycycline; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside
keywords: Bmp4; Mesenchymal-epithelial interactions; Mouse; Ocular surface; Precocious epithelium stratification; Wnt/β-catenin signaling