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Dev Biol September 1, 1995; 171 (1): 240-51.
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Autonomous endodermal determination in Xenopus: regulation of expression of the pancreatic gene XlHbox 8.

Gamer LW , Wright CV .

In neural plate stage Xenopus embryos, XlHbox 8 expression marks anterior endodermal cells fated to develop into pancreas/duodenum, and expression continues in adult pancreas in exocrine duct, acinar, and islet cells. Here, XlHbox 8 is used as a marker in experiments addressing the mechanisms of early endodermal patterning, particularly with respect to the role of specific polypeptide growth factors. When mesoderm-free vegetal explants (VEs) from early blastula stage embryos are cultured in isolation, XlHbox 8 expression develops autonomously in the dorsal region, strongly suggesting that endodermal region-specific determination occurs before MBT. Data from microinjection experiments using RNA encoding the activin and FGF dominant negative receptors and growth factor treatments of isolated VEs suggest that activin positively regulates XlHbox 8 expression, whereas bFGF is a potent negative regulator. Moreover, bFGF induces mesodermal marker expression in VEs. This suggests that the early endodermal determination state is plastic and that elevated levels of bFGF may convert vegetal (endodermal) cells into mesoderm. We propose a model for XlHbox 8 regulation in which an early signal from the Nieuwkoop center (whose eventual fate is endoderm) predisposes dorsovegetal cells for autonomous XlHbox 8 expression, in an area of high local activin (or activin-like) ligand concentration, and low relative concentrations of bFGF.

PubMed ID: 7556900
Article link: Dev Biol
Grant support: [+]

Species referenced: Xenopus
Genes referenced: actl6a bmp4 fgf2 fgfr1 gcg gdf1 ins nog pdx1 sst.1 tbxt yes1
Antibodies: Gcg Ab2 Gut Ab1 Ins Ab2 Pdx1 Ab1 Pdx1 Ab2

Article Images: [+] show captions