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The structure and development of Xenopus laevis cornea.

Hu, W; Haamedi, N; Kinoshita, T; Ohnuma, SI; (2013) The structure and development of Xenopus laevis cornea. Exp Eye Res , 116 pp. 109-128. 10.1016/j.exer.2013.07.021. Green open access

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Abstract

The African clawed frog, Xenopus laevis, is a widely used model organism for tissue development. We have followed the process of corneal development closely in Xenopus and examined the corneal ultrastructure at each stage during its formation. Xenopus cornea development starts at stage 25 from a simple embryonic epidermis overlying the developing optic vesicle. After detachment of the lens placode which takes place around stage 30, cranial neural crest cells start to invade the space between the lens and the embryonic epidermis to construct the corneal endothelium. At stage 41, a second wave of migratory cells containing presumptive keratocytes invades the matrix leading to the formation of inner cornea and outer cornea. Three-dimensional electron microscopic examination shows that a unique cell mass, the stroma attracting center, connects the two layers like the center pole of a tent. After stage 48, many secondary stromal keratocytes individually migrate to the center and form the stroma layer. At stage 60, the stroma space is largely filled by collagen lamellae and keratocytes, and the stroma attracting center disappears. At early metamorphosis, the embryonic epithelium gradually changes to the adult corneal epithelium, which is covered by microvilli. Around stage 62 the embryonic epithelium thickens and a massive cell death is observed in the epithelium, coinciding with eyelid opening. After metamorphosis, the frog cornea has attained the adult structure of three cellular layers, epithelium, stroma, and endothelium, and two acellular layers between the cellular layers, namely the Bowman's layer and Descemet's membrane. After initial completion, Xenopus cornea, in particular the stroma, continues to thicken and continues to enlarge throughout the lifetime of the animal. In the adult, a p63 positive limbus-like wavy structure is observed at the peripheral edge of the cornea. Proliferation analysis shows that the basal corneal epithelial cells actively divide and there are a small number of proliferating cells among the stroma and endothelial cells. This study shows that the development and structure of Xenopus cornea is largely conserved with human although there are some unique processes in Xenopus.

Type: Article
Title: The structure and development of Xenopus laevis cornea.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.exer.2013.07.021
Publisher version: http://dx.doi.org/10.1016/j.exer.2013.07.021
Additional information: �© 2013 The Authors. Published by Elsevier Ltd. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: CMZ, NCC, SAC, Xenopus, amphibian, cell death, ciliary marginal zone, cornea, development, embryo, eye, metamorphosis, neural crest, neural crest cell, stroma-attracting center
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > Institute of Ophthalmology
URI: https://discovery.ucl.ac.uk/id/eprint/1405967
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