Expression of the homeobox gene Hex during early stages of chick embryo development

Whole mount in situ hybridization studies were performed to investigate the expression pattern of the homeobox gene Hex (also known as Prh) during ear ly stages of chick embryogenesis. At the time of laying, cHex transcripts a re detected in Koller's a sickle and the forming hypoblast. During gastrula tion (HH stage 4), cHex is expressed in anteriorly-displaced hypoblast cell s. At stage 6, cHex transcripts are observed within endoderm in an anterior are that overlaps the cardiogenic region. Later cHex expression is observe d within pharyngeal endoderm immediately adjacent to the forming myocardium , in the endocardium and in the liver and thyroid gland primordia. cHex tra nscripts are also detected within blood islands beginning at stage 4, and i n extraembryonic and intraembryonic vascular endothelial cells as vessels f orm. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.