A gene encoding embryonic chicken pepsinogen (ECPg), a zymogen of the digestive enzyme pepsin, is expressed specifically in epithelial cells of glands of embryonic stage proventriculus (glandular stomach) under the influence of mesenchyme. We found four GATA and one Sox binding motifs in 1.1 kb of the 5' flanking region of the ECPg gene which are essential to the organ-specific expression of the gene. The expression of cGATA-5 and cSox2 in the proventriculus from day 6 to day 12 of incubation was therefore analyzed. cGATA-5 was more strongly expressed in glandular epithelial cells than in luminal epithelial cells, while cSox2 gene expression was weaker in glandular epithelial cells. Using heterologous recombination explants we also discovered that the expression of cGATA-5 and cSox2 in epithelial cells was affected by mesenchyme when the latter induced ECPg gene expression in epithelial cells. Introduction of expression constructs into epithelial cells by electroporation demonstrated that cGATA-5 upregulated transcription of a reporter luciferase gene via a cis element in the 5' flanking region of the ECPg gene. The gel mobility shift assay revealed that the cGATA-5 protein specifically binds to the GATA binding sites. cSox2 downregulated the activity of luciferase but it was not through the Sox binding motif. These results suggest that cGATA-5 positively regulates transcription of the ECPg gene and is involved in spatial regulation of the pepsinogen gene during development.

No abstract

Genes encoding pepsinogens, zymogens of digestive enzyme pepsins, are expressed specifically in the gland epithelial cells of the vertebrate stomach, and their expression is also developmentally regulated, therefore providing a good model for the analysis of transcriptional regulation of genes. In the development of chicken embryonic stomach, the epithelium invaginates into the mesenchyme and forms glands and gland epithelial cells then begin to express embryonic chicken pepsinogen (ECPg) gene. It has been shown that cGATA5 binds directly GATA binding sites located within 1.1-kbp upstream of ECPg gene and activates its transcription. To find more precisely the sequences necessary for ECPg gene transcription, we carried out deletion and mutation analysis with 1.1-kbp upstream region. The results suggest that binding of GATA factor to three GATA binding sites within the upstream region ؊656 to ؊419 synergistically regulates ECPg expression in the gland epithelial cells. Developmental Dynamics 228:51-58, 2003.