Int. J. Dev. Biol. 48: 275 - 283 (2004)
doi: 10.1387/ijdb.041805kt
© UBC Press

Xantivin suppresses the activity of EGF-CFC genes to regulate nodal signaling

Kousuke Tanegashima1, Yoshikazu Haramoto1, Chika Yokota1, Shuji Takahashi1 and Makoto Asashima*,1, 2

1Department of Life Sciences (Biology), University of Tokyo, Komaba, Tokyo, Japan, 2SORST project, Japan Science and Technology Corporation (JST), Japan

ABSTRACT Lefty, antivin and related genes act in a feedback inhibition mechanism for nodal signaling at a number of stages of vertebrate embryogenesis. To analyze the function of the feedback inhibitor of nodal signaling, Xantivin in Xenopus embryos, we designed a morpholino antisense oligonucleotide (XatvMO) for this gene. XatvMO caused the expansion of mesodermal tissue and head defects. XatvMO-injected gastrulae showed up-regulated expression of the mesodermal markers Xbra, Xwnt8, Xnot, and Chordin, suggesting expansion of the trunk-tail organizer. As expected, depletion of Xantivin also up-regulated nodal signaling as confirmed by the enhanced ectopic expression of Xantivin mRNA, a known target gene of nodal signaling. Furthermore, we investigated the relationship between Xantivin and the EGF-CFC gene FRL-1, which is a component of the nodal receptor. In animal cap assays, FRL-1 could not induce expression of nodal-responsive genes, but could up-regulate expression of these genes when FRL-1 was coinjected with a low dose of Xnr1; coinjection of Xantivin suppressed this up-regulation by FRL-1. We also found that Xantivin can rescue the caudalized phenotype induced by overexpression of FRL-1. Co-immunoprecipitation assays showed that Xantivin interacted with the EGF-CFC proteins, FRL-1 and cripto. Taken together, these results suggest that Xantivin opposes the activity of EGF-CFC genes and thereby antagonizes nodal signaling.

Keywords:

nodal, antivin, lefty, EGF-CFC gene, Xenopus laevis

*Corresponding author e-mail: asashi@bio.c.u-tokyo.ac.jp