Early expression of hypoxia-inducible factor 1alpha in the chicken embryo.

Hypoxia is known to regulate angiogenesis and tissue growth by the induction of the alpha subunit of the heterodimeric transcription factor, hypoxia-inducible factor 1. The expression pattern of HIF1alpha in both epithelial and mesenchymal structures of the chicken embryo through the first 7 days of development is reported here. HIF1alpha transcript is expressed diffusely throughout the neuroepithelium, limb, mesonephritic and cephalic mesenchyme, progressively becoming restricted to known proliferative zones of the central nervous system. Specific, strong expression is unexpectedly found in the endoderm of Sessel's pouch and in the ectoderm of both Rathke's pouch and the first branchial arch before the disappearance of the buccopharyngeal membrane.