Interaction of Wnt and
caudal-related genes in zebrafish posterior body formation
Shimizu T, Bae Y K, Muraoka O and Hibi M
Dev Biol 279(1):125-41 (2005)
SUMMARY
Although Wnt signaling plays an important role in body patterning during
early vertebrate embryogenesis, the mechanisms by which Wnts control the
individual processes of body patterning are largely unknown. In zebrafish,
wnt3a and wnt8 are expressed in overlapping domains in the blastoderm
margin and later in the tailbud. The combined inhibition of Wnt3a and
Wnt8 by antisense morpholino oligonucleotides led to anteriorization of
the neuroectoderm, expansion of the dorsal organizer, and loss of the
posterior body structure-a more severe phenotype than with inhibition
of each Wnt alone-indicating a redundant role for Wnt3a and Wnt8. The
ventrally expressed homeobox genes vox, vent, and ved mediated Wnt3a/Wnt8
signaling to restrict the organizer domain. Of posterior body-formation
genes, expression of the caudal-related cdx1a and cdx4/kugelig, but not
bmps or cyclops, was strongly reduced in the wnt3a/wnt8 morphant embryos.
Like the wnt3a/wnt8 morphant embryos, cdx1a/cdx4 morphant embryos displayed
complete loss of the tail structure, suggesting that Cdx1a and Cdx4 mediate
Wnt-dependent posterior body formation. We also found that cdx1a and cdx4
expression is dependent on Fgf signaling. hoxa9a and hoxb7a expression
was down-regulated in the wnt3a/wnt8 and cdx1a/cdx4 morphant embryos,
and in embryos with defects in Fgf signaling. Fgf signaling was required
for Cdx-mediated hoxa9a expression. Both the wnt3a/wnt8 and cdx1a/cdx4
morphant embryos failed to promote somitogenesis during mid-segmentation.
These data indicate that the cdx genes mediate Wnt signaling and play
essential roles in the morphogenesis of the posterior body in zebrafish.
LINK
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