Endoderm induction by the organizer-secreted factors chordin and noggin in Xenopus animal caps.
Spemann's organizer has potent neural inducing and mesoderm dorsalizing activities in the Xenopus gastrula. A third activity, the organizer's ability to induce a secondary gut, has been difficult to analyze experimentally due to the lack of early gene markers. Here we introduce endodermin, a pan-endodermal gene marker, and use it to demonstrate that chordin (Chd), a protein secreted by the organizer region, is able to induce endodermal differentiation in Xenopus. The ability of chd, as well as that of noggin, to induce endoderm in animal cap explants is repressed by the ventralizing factor BMP-4. When FGF signaling is blocked by a dominant-negative FGF receptor in chd-injected animal caps, neural induction is inhibited and most of the explant is induced to become endoderm. The results suggest that proteins secreted by the organizer, acting together with known peptide growth factors, regulate differentiation of the endodermal germ layer.
Sasai
Y
Y
Department of Biological Chemistry, University of California, Los Angeles 90095-1737, USA.
Lu
B
B
Piccolo
S
S
De Robertis
E M
EM
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D002454:Cell Differentiation; D004627:Embryonic Induction; D004707:Endoderm / Q000166:cytology; D005346:Fibroblast Growth Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D005819:Genetic Markers; D006023:Glycoproteins / Q000235:genetics*; D036341:Intercellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics*; D015398:Signal Transduction; D014981:Xenopus / Q000196:embryology; D000099176:Noggin Protein
D002352:Carrier Proteins; D005346:Fibroblast Growth Factors; D005819:Genetic Markers; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D011506:Proteins; D000099176:Noggin Protein; C054234:chordin