HESX Homeobox Protein 1 (HESX1)

The 185-amino acid open reading frame is highly conserved compared with the mouse and Xenopus sequences. As gastrulation progresses, Hesx1 transcripts appear in the adjacent ectoderm which is destined to give rise to the ventral prosencephalon, and this ectodermal expression appears to require an inductive signal from the visceral endoderm. Subsequently, Hesx1 is expressed at the anterior extreme of the rostral neural folds, finally resolving to the ventral diencephalon at 9.0 days postcoitum. At this stage, Hesx1 is also expressed in the thickened layer of oral ectoderm which will give rise to the Rathke pouch, the primordium of the anterior pituitary. Ultimately, transcripts become restricted to the Rathke pouch. Downregulation of Hesx1 in the pouch coincides with the differentiation of pituitary-specific cell types.