DIFFERENTIATION OF AVIAN DIGESTIVE TRACT EPITHELIUM IN VITRO

Abstract

Avian embryonic digestive tract has been used for the analysis of epithelialmesenchymal interactions in the organogenesis. Many tissue recombination experiments carried out so far demonstrated that the morphological differentiation of the epithelium is often determined by the influences of the mesenchyme, whereas the functional, molecular differentiation depends on both the mesenchymal influence and the reactivity of the epithelium. The epithelium of the avian embryonic digestive tract can be classified into two parts : cells in one part can express pepsinogen gene, a marker gene of the proventriculus (glandular stomach) under certain conditions and cells in another part never express it. The expression of ECPg gene in epithelial cells is controlled by the action of the mesenchyme, through 5' promoter region of ECPg gene. The establishment of two quantitatively different parts in digestive tract epithelium occurs just after the formation of endoderm, and is considered to be accompanied by the expression of some homeobox genes. The elucidation of functions of these genes may greatly contribute to the understanding of the mechanisms underlying organogenesis of many organ systems.