Plakoglobin Is an Important Adhesion Protein in the Developing Early Human Corneal Epithelium

Abstract

Purpose: : The purpose of this study was to investigate the presence and the distribution of plakoglobin in the developing early human corneal epithelium.

Methods: : Five embryos and eight fetuses (ranged from 10-111 mm crown-rump length (CRL) corresponding to 6th-14th ovulation weeks) were obtained from spontaneous and legal abortions according to the Helsinki Declaration II. By use of an immunohistochemical method plakoglobin was identified.

Results: : In the 7^th week the ectoderm covering the early cornea is almost plakoglobin-negative, whereas the fornical ectoderm is strongly positive to plakoglobin (figure). In the beginning of the 9^th week the eyelids are fused and plakoglobin is still predominantly expressed in the fornical ectoderm. In the 14^th week the early limbal region is being formed beneath the limbal ectoderm and few goblet cells are seen in the periphery of the ocular surface and plakoglobin is now being expressed in the central epithelium, but is more abundant in the limbal ectoderm.

Conclusions: : Plakoglobin is a member of the β-catenin family and it has been found in basal functional cell studies, that N-cadherin is being processed in endoplasmatic reticulum and associates with plakoglobin in the Golgi network and in the cytosol. The complex is being transported to the plasma membrane, where it links to the actin cytoskeleton. N-cadherin has recently been proposed as a putative limbal stem cell marker. We have previously shown that plakoglobin changes intracellular location in the corneal epithelium during migration from limbus to central cornea in adults. In the limbal epithelium plakoglobin is mainly expressed in the cytoplasm, while plakoglobin is expressed in the cell membrane in the central epithelium. The early appearance of plakoglobin in the developing corneal epithelium and especially its fornical-limbal location underlines that plakoglobin is important regarding proliferation, migration and differentiation.

Keywords: cornea: basic science • cornea: epithelium • protein purification and characterization