Click here to close Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly. We suggest using a current version of Chrome, FireFox, or Safari.
XB-ART-36874
Mech Dev January 1, 2008; 125 (1-2): 58-66.

Expression of Siamois and Twin in the blastula Chordin/Noggin signaling center is required for brain formation in Xenopus laevis embryos.

Ishibashi H , Matsumura N , Hanafusa H , Matsumoto K , De Robertis EM , Kuroda H .


Abstract
The blastula Chordin- and Noggin-expressing (BCNE) center located in the dorsal animal region of the Xenopus blastula embryo contains both prospective anterior neuroectoderm and Spemann organizer precursor cells. Here we show that, contrary to previous reports, the canonical Wnt target homeobox genes, Double knockdown of these genes using antisense morpholinos in Xenopus laevis blocked head formation, reduced the expression of the other BCNE center genes, upregulated Bmp4 expression, and nullified hyperdorsalization by lithium chloride. Moreover, gain- and loss-of-function experiments showed that Siamois and Twin expression is repressed by the vegetal transcription factor VegT. We propose that VegT expression causes maternal beta-Catenin signals to restrict Siamois and Twin expression to the BCNE region. A two-step inhibition of BMP signals by Siamois and Twin-- first by transcriptional repression of Bmp4 and then by activation of the expression of the BMP inhibitors Chordin and Noggin--in the BCNE center is required for head formation.

PubMed ID: 18036787
PMC ID: PMC2292103
Article link: Mech Dev
Grant support: [+]
Genes referenced: bmp4 chrd.1 mix1 nodal nog otx2 sia1 sia2 vegt ventx1.2 wnt8a
Morpholinos: chrd MO10 chrd MO8 ctnnb1 MO1 nog MO1 sia1 MO1 sia2 MO1 vegt MO4


Article Images: [+] show captions
References:
Agius, 2000, Pubmed, Xenbase [+]


Xenbase: The Xenopus laevis and X. tropicalis resource.
Version: 4.11.2


Major funding for Xenbase is provided by grant P41 HD064556