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Yujin Zhang, Winston W-Y Kao, Sr., Chia-Yang Liu, Sr.; Conditional Knock-out β-catenin Disrupts Mouse Fetal Eyelid Morphogenesis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2093.
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Wnt signaling plays pivotal roles in tissue morphogenesis. In this study, attmepts were made to examine the role of Wnt/β-catenin pathway in eyelid morphogenesis.
RT-PCR and immunofluoresecne staining were employed to determine the expression of Wnts and cellular localization of Ctnnb1 in eyelid during embryonic development. The driver Kera-rtTA (KR), tet-O-Cre (TC) and β-catenin flox (Ctnnb1f/f) mice were crossed to obtain triple transgenic mice KR/TC/ Ctnnbf/f in which Ctnnb1 was ablated by feeding pregnant dams with Dox-chow commenced at the beginning of mating (E0) continued to various gestation stages e.g., E14.5, E15.5, E16.5 and postnatal day 1 when embryos and neonates were collected. The specimens were then subjected to histology and immunohistochemistry examination.
Wnt ligands including Wnt3, Wnt5a, Wnt8a, Wnt9a, Wnt9b, Wnt11 and Wnt16 were expressed by eyelid mesenchymal cells as detected by RT-PCR. Immunofluorescence staining indicated that there was a translocation of Ctnnb 1 from plasmic membrane at E13.5 to nuclei at E15.5. The ablation of β-catenin in eyelid mesenchymal cells caused anomaly of the formation of bilateral concaved eyelids at birth. Histological examinations showed that eyelid epithelium of both wild-type and β-catenin lof-mutant (lost of function) mice began to migrate at E14.5. However, the concurrent growth of eyelid stroma and subsequent eyelid closure were disrupted in β-catenin lof mutant, which normally take place at E16.5. Lof mutants also had thinner corneal stroma than that of wild type mice. It was noteworthy that number of BrdU-labeled eyelid mesenchymal cells in lof mutant is 5-fold less than that of wild type, while TUNEL assay did not show any noticeable difference. Immunohistochemistry showed that there was a upregulation of phospho-p38 but phospho-ERK was not affected in mesenchymal cells of lof mutant at E15.5.
These findings suggested that the eyelid malformation caused by ablation of Ctnnb1 may be due to reduced proliferation and/or perturbed migration of periocular mesenchymal cell of neural crest origin. Canonical Wnt/β-catenin signaling in periocular mesenchymal cells plays a pivotal role for the eyelid morphogenesis during mouse embryonic development.
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