• HIF-1α;
  • hypoxia;
  • Xenopus;
  • transgenesis;
  • promoter;
  • A6 cell line


Hypoxia-inducible factor 1α (HIF-1α) plays a central role in regulating oxygen-dependent gene expression and is involved in a range of pathways implicated in cellular survival, proliferation, and development. While the posttranslational regulation of HIF-1α is well characterized, the relative importance of its control at the transcriptional level during development remains less clear. Although the mouse and human promoter regions have been analyzed in vitro, to date, there has been no in vivo analysis of any vertebrate HIF-1α promoter. To investigate the transcriptional regulation of HIF-1α during development of the amphibian Xenopus laevis, we have described the gene's expression pattern and isolated the xHIF-1α upstream regulatory regions. We show xHIF-1α mRNA to be constitutively expressed at low levels throughout embryogenesis, but with significant up-regulation during gastrula stages, and subsequently, in specific regions of the central nervous system and axial tissues. Our functional analysis using a series of truncated xHIF-1α promoter constructs demonstrates that a 173-bp region of the proximal promoter, which is 100% conserved among five allelic variants, is sufficient to drive correct expression in transgenic embryos. Although these results are corroborated by a parallel set of in vitro transfection experiments in a Xenopus cell line, some key differences suggest the importance of using transgenic methods in conjunction with in vitro assays. Developmental Dynamics 230:229–238, 2004. © 2004 Wiley-Liss, Inc.