GEP31, A NEW GASTRIC EPITHELIAL PROTEIN, EARLY EXPRESSED DURING ONTOGENY

A set of monoclonal antibodies directed against various gastric marker s was produced in order to study the developmental expression of the g astric mucosa. A previously described monoclonal antibody, mab 146.14, labeled the proton pump (H+, K+) ATPase specifically located in gastr ic parietal cells. Mabs 15.1 and 121.17 revealed the mucus of mucous n eck cells and mucous surface cells, respectively. By addition, mab 81. 1 was directed against a cell surface membrane protein antigen compose d of a major 31 kDa component (called GEP31). Our study mainly focused on the characterization of GEP31. This protein was typically located in the gastrointestinal epithelial tract (stomach, small intestine, co lon). Moreover, interesting features were observed during the study of the early ontogenesis of the gastric mucosa. The 31 kDa protein was d etected at the onset of gland formation (day 18), and a gradual increa se in expression of the protein could be observed between day 18 and d ay 19. Furthermore, a comparative study of the expression of different terminal differentiation markers of gastric epithelial cells ((H+, K) ATPase, mucins) during the early period of ontogenesis revealed that GEP31 could be detected well before the appearance of these markers. To our knowledge, GEP31 thus appears as the earliest expressed specifi c cell surface epithelial gastric antigen described to date. Furthermo re, the partial N-terminal amino acid sequence of GEP31 was determined and revealed that it is not a known protein.