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Proc Natl Acad Sci U S A November 25, 1997; 94 (24): 13017-22.

Siamois is required for formation of Spemann''s organizer.

Spemann''s organizer develops in response to dorsal determinants that act via maternal components of the wnt pathway. The function of siamois, a wnt-inducible homeobox gene, in Spemann''s organizer development was examined by fusion of defined transcriptional regulatory domains to the siamois homeodomain. Similar to native siamois, a VP16 activator fusion induced axis formation, indicating that siamois functions as a transcriptional activator in axis induction. Fusion of the engrailed repressor generated a dominant inhibitor that blocked axis induction by Xwnt8, beta-catenin, and siamois, and repressed wnt activation of the goosecoid promoter. Dorsal injection of the engrailed-siamois fusion resulted in complete inhibition of dorsal development and organizer gene expression, an effect rescued by siamois, but not by Xwnt8 or beta-catenin. Thus, as a zygotic mediator of maternal dorsal signals, siamois function is required for development of Spemann''s organizer.

PubMed ID: 9371792
PMC ID: PMC24255
Article link: Proc Natl Acad Sci U S A
Grant support: [+]

Species referenced: Xenopus
Genes referenced: cer1 chrd.1 eng fst gsc nodal3.2 nog sia1 tbxt wnt8a

Article Images: [+] show captions
References [+] :
Badiani, Dominant interfering alleles define a role for c-Myb in T-cell development. 1994, Pubmed