XB-ART-9239Int J Dev Biol January 1, 2001; 45 (1): 237-40.
Work in amphibians indicates that inhibition of Wnt and BMP signals is essential for head development and that head induction by the Spemann-Mangold organizer may be mediated by secreted Wnt antagonists. Wnts are potent posteriorizing factors and antagonize the Spemann-Mangold organizer. Dickkopf1 (dkk1) encodes a secreted effector expressed in head organizing centers of Xenopus, mouse and zebrafish. It acts as a Wnt inhibitor and is able together with BMP inhibitors to induce the formation of ectopic embryonic heads in Xenopus. It anteriorizes both mesendoderm and neuroectoderm, promoting prechordal plate and forebrain fates. Injection of inhibitory antibodies leads to microcephaly and cyclopia. Dkk1 thus is an essential mediator of the vertebrate head organizer.
PubMed ID: 11291852
Article link: Int J Dev Biol
Genes referenced: bmpr1a cer1 dkk1 frzb gsc hhex lefty nog prdm1 tbx2
Antibodies: Dkk1 Ab1
Article Images: [+] show captions
|Fig. 2. Expression of dickkopf1 in vertebrates. (A) Late gastrula zebrafish. Dorsal to the right; anterior, top (from M. Furutani-Seiki, with permission). (B) Midgastrula Xenopus. Dorsal to the right; anterior, top (Glinka et al., 1998). (C) Early gastrula mouse. Anterior, left (Glinka et al., 1998). Arrows point to dkk1 expression in presumptive prechordal endomesoderm.|
|Fig. 3. Head induction by dickkopf1. (A) A tadpole-stage embryo that has been injected with mRNA encoding a dominant-negative BMP receptor (tBR) and dkk1 forms a complete secondary head. (B) A tadpole embryo microinjected with inhibitory anti-Dkk1 antibodies. The experimental embryo lacks anterior head structures (Glinka et al., 1998 and unpublished).|