Region-Specific Expression of Chicken Sox2 in the Developing Gut and Lung Epithelium: Regulation by Epithelial-Mesenchymal Interactions

In situ analysis of the chicken cSox2 gene, a member of the transcription factor family containing an Sry-like high-mobility group (HMG) box, demonstrated localized expression in the embryonic endoderm. Transcripts of cSox2 appeared before commencement of morphogen- esis and cytodifferentiation in the rostral gut epithelium from the pharynx to the stomach. The caudal limit of cSox2 expression coincided with that of the region competent for proventricular differentiation and to the rostral limit of the domain of CdxA, a homologue of Drosophila cau- dal. During morphogenesis, the level of tran- scripts of cSox2 decreased in epithelia invaginat- ing into surrounding mesenchyme to form glandular or tubular structures, such as the pri- mordia of the thyroid and lung, glandular epithe- lium of the proventriculus, and secondary bron- chus of the lung. Tissue recombination experiments demonstrated that cSox2 expression is regulated by the underlying mesenchyme as well as morpho- genesis and cytodifferentiation. The results sug- gest that cSox2 plays pivotal roles in generating morphologically and physiologically distinct types of epithelial cells in the gut. Dev. Dyn. 1998;213:464-475. r 1998 Wiley-Liss, Inc.