Immunohistochemical Detection of an Epithelial Membrane Protein in Rat Embryos at Different Stages of Development

Abstract

This study aimed to describe the distribution of a membrane protein called Gz-1-Ag in embryonal rat tissues using monoclonal antibodies. Three monoclonal antibodies recognizing different antigenic determinants of Gz-1-Ag were tested on different stages of rat embryos – fertilized oocytes two-cell stages morulae blastocysts and embryos up to 17.5 days old.The embryos were fixed by different methods; the Tokuyasu method was the most convenient. It yielded very good morphological conservation, good preservation of antigenicity and weak background fluorescence. Gz-1-Ag was detected in practically all early epithelial structures, but the intensity of fluorescence varied. Fluorescence was not associated with the germ layer from which the epithelium derived. The uninterrupted presence of Gz-1-Ag from the fertilized oocyte to all subsequently arising epithelial structures suggests a role of Gz-1-Ag in cell adhesion secretory processes or the intercellular exchange of information or substances.

EpCAM in morphogenesis

“…EpCAM is expressed from the earliest developmental stages. For instance, EpCAM is already present at the two cell stage and the morula stage (13). This is particularly interesting, since these early stages, do not contain epithelial cells yet.…”

“…De Boer et al, identified that EpCAM was dynamically expressed in adult, normal, regenerating, metaplastic, and neoplastic liver, which together led them to hypothesize that EpCAM was associated with liver development (12). The hypothesis that EpCAM is a morphoregulatory protein is in line with the expression pattern of the rat homologue of EpCAM during rat development (13). Moreover, it is in line with the fact that addition of an anti-EpCAM antibody inhibits the differentiation of fetal pancreatic cells into pancreatic epithelial cells (11).…”

Epithelial Cell Adhesion Molecule

“…Similarly, Ep-CAM is expressed in the first developmental stages, ie, in fertilized oocytes, at the two-cell stage and in the morula. 12 Moreover, expression of classic CAMs is found on embryonic stem cells, which is not surprising because cell-cell interactions are crucial for differentiation. Likewise, in murine embryonic stem cells, expression of the murine homologue of EpCAM has been found.…”

Expression of nestin–green fluorescent protein transgene marks oval cells in the adult liver

“…The epithelium-specific cell adhesion molecule EpCAM is expressed by almost all epithelial cells, except for hepatocytes and differentiated keratinocytes. In adult mouse liver, EpCAM is expressed in all cholangiocytes (Tarmann et al, 1990; for review, see Balzar et al, 1999). Most GFP-positive cells in the quiescent liver of nestin-GFP animals are EpCAM positive (Fig.…”