REGULATION OF PEPSINOGEN GENE-EXPRESSION IN EPITHELIAL-CELLS OF VERTEBRATE STOMACH DURING DEVELOPMENT

Pepsinogens are zymogens of pepsins, aspartic proteases working as dig estive enzymes in the vertebrate stomach, of which biological and mole cular properties have been extensively studied. In developmental biolo gy, pepsinogens offer excellent molecular markers of differentiation o f stomach epithelial cells, since their expression is strictly limited to those cells and there are some isozymes that are expressed in deve lopmental stage-specific manner. It is now well established that the e xpression of embryonic chicken pepsinogen (ECPg) gene is regulated by epithelial-mesenchymal interactions: it is mesenchyme that determines the expression pattern of ECPg along the digestive tract, by supportin g or inhibiting the intrinsically endowed ability of epithelial cells to express it. In the present review article, I will describe recent m olecular biological and experimental embryological consequences of our studies on the regulation of ECPg expression by mesenchymal cells, wi th special attention to the nature of mesenchymal factors and the mole cular mechanisms of reactivity of epithelial cells to the mesenchymal influences.