WNT signals control FGF-dependent limb initiation and AER induction in the chick embryo.
A regulatory loop between the fibroblast growth factors FGF-8 and FGF-10 plays a key role in limb initiation and AER induction in vertebrate embryos. Here, we show that three WNT factors signaling through beta-catenin act as key regulators of the FGF-8/FGF-10 loop. The Wnt-2b gene is expressed in the intermediate mesoderm and the lateral plate mesoderm in the presumptive chick forelimb region. Cells expressing Wnt-2b are able to induce Fgf-10 and generate an extra limb when implanted into the flank. In the presumptive hindlimb region, another Wnt gene, Wnt-8c, controls Fgf-10 expression, and is also capable of inducing ectopic limb formation in the flank. Finally, we also show that the induction of Fgf-8 in the limb ectoderm by FGF-10 is mediated by the induction of Wnt-3a. Thus, three WNT signals mediated by beta-catenin control both limb initiation and AER induction in the vertebrate embryo.
Kawakami
Y
Y
The Salk Institute for Biological Studies, Gene Expression Laboratory, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
Capdevila
J
J
Büscher
D
D
Itoh
T
T
Rodríguez Esteban
C
C
Izpisúa Belmonte
J C
JC
D000818:Animals; D030161:Avian Proteins; D002642:Chick Embryo / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000502:physiology; D004475:Ectoderm / Q000502:physiology; D051526:Fibroblast Growth Factor 10; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D018878:Limb Buds / Q000502:physiology*; D008648:Mesoderm / Q000502:physiology; D008934:Mitogens / Q000502:physiology; D009024:Morphogenesis; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D015534:Trans-Activators; D014921:Wings, Animal / Q000196:embryology; D051153:Wnt Proteins; D051154:Wnt2 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin
D030161:Avian Proteins; D003598:Cytoskeletal Proteins; D051526:Fibroblast Growth Factor 10; D008934:Mitogens; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051153:Wnt Proteins; C424042:Wnt-2b protein, Gallus gallus; D051154:Wnt2 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin; D051524:Fibroblast Growth Factor 8; D005346:Fibroblast Growth Factors