Zebrafish Cornea: Structure, Early Development, and Comparison of Wild Type and Mutants

Abstract

Abstract: : Purpose: Zebrafish is an excellent animal model for eye development and vision disorders. Despite extensive embryological and genetic analysis of the zebrafish eye, little is known about its cornea and the genetic mechanisms of its development. One of the goals of this study is to provide a comprehensive description of this tissue. This type of analysis is essential for future genetic studies of this tissue. Methods: Dissected eyes from adult fish and embryos were collected and processed for light and electron microscopic analysis and for immunohistochemical experiments. Antibodies that were raised against known corneal proteins were tested. Zebrafish mutants were included in this study to see if they display cornea–specific defects. Results: The cornea of adult fish contains all 5 major layers found in the human cornea. Light and electron microscopic analysis demonstrates that the adult zebrafish cornea shows a striking similarity to the human cornea. This conservation in structure is further evidenced by comparable expression patterns of important corneal structural proteins. Analysis of embryos of early development indicates that the zebrafish cornea develops very rapidly in embryogenesis. Corneal defects are detected in two zebrafish mutants. BIGH3, a human corneal dystrophy gene, is highly conserved in its protein sequence and its corneal expression pattern between human and zebrafish. Conclusions: The structural and compositional similarity of human and zebrafish corneas strongly supports the potential that zebrafish is a suitable model for corneal studies. The BIGH3 gene is a promising candidate gene for developing a transgenic fish with corneal dystrophy.

Keywords: anatomy • microscopy: electron microscopy • cornea: basic science