Y. Marikawa et Rp. Elinson, BETA-TRCP IS A NEGATIVE REGULATOR OF THE WNT BETA-CATENIN SIGNALING PATHWAY AND DORSAL AXIS FORMATION IN XENOPUS EMBRYOS/, Mechanisms of development, 77(1), 1998, pp. 75-80
The Wnt/beta-catenin signaling pathway is responsible for the establis
hment of the dorsoventral axis of Xenopus embryos. The recent finding
of the F-box/WD40-repeat protein slimb in Drosophila, whose loss-of-fu
nction mutation causes ectopic activation of wingless signaling (Jiang
, J., Struhl, G., 1998. Nature 391, 493-496), led us to examine the ro
le of its vertebrate homolog beta-TrCP in Wnt/beta-catenin signaling a
nd dorsal axis formation in Xenopus embryos. Co-injection of beta-TrCP
mRNA diminished Xwnt8 mRNA-induced axis formation and expression of S
iamois and Xnr3, suggesting that beta-TrCP is a negative regulator of
the Wnt/beta-catenin signaling pathway. An mRNA for a beta-TrCP mutant
construct (Delta F), which lacked the F-box domain, induced an ectopi
c axis and expression of Siamois and Xnr3. Because this activity of De
lta F was suppressed by co-injection of beta-TrCP mRNA, Delta F likely
acts in a dominant negative fashion. The activity of Delta F was dimi
nished by C-cadherin, glycogen synthase kinase 3 and Axin, but not by
a dominant negative dishevelled. These results suggest that beta-TrCP
can act as a negative regulator of dorsal axis formation in Xenopus em
bryos. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.