To contribute to an understanding of the roles and mechanisms of action of Wnts in early vertebrate development, we have characterized the normal expression of Xenopus laevis Wnt-5A, and investigated the consequences of misexpression of this putative signalling factor. Xwnt-5A transcripts are expressed throughout development, and are enriched in both the anterior and posterior regions of embryos at late stages of development, where they are found primarily in ectoderm, with lower levels of expression in mesoderm. Overexpression of Xwnt-5A in Xenopus embryos leads to complex malformations distinct from those achieved by ectopic expression of Xwnts −1, −3A, or −8. This phenotype is unlikely to result from Xwnt-5A acting as an inducing agent, as overexpression of Xwnt-5A does not rescue dorsal structures in UV-irradiated embryos, does not induce mesoderm in blastula caps, and Xwnt-5A does not alter the endogenous patterns of expression of goosecoid, Xbra, or Xwnt-8. To pursue whether Xwnt-5A has the capacity to affect morphogenetic movements, we investigated whether overexpression of Xwnt-5A alters the normal elongation of blastula cap explants induced by activin. Intriguingly, Xwnt-5A blocks the elongation of blastula caps in response to activin, without blocking the differentiation of either dorsal or ventral mesoderm within these explants. The data are consistent with Xwnt-5A having the potential activity of modifying the morphogenetic movements of tissues.

REFERENCES

Bradley
R. S.
,
Brown
A. M. C.
(
1990
).
The proto-oncogene int- 1 encodes a secreted protein associated with the extracellular matrix.
EMBO J
9
,
1569
1575
Christian
J. L.
,
Gavin
B. J.
,
McMahon
A. P.
,
Moon
R. T.
(
1991
).
Isolation of cDNAs partially encoding four Xenopus Wnt −1/ int −1-related proteins and characterization of their transient expression during embryonic development.
Dev. Biol
143
,
230
234
Christian
J. L.
,
McMahon
J. A.
,
McMahon
A. P.
,
Moon
R. T.
(
1991
).
Xwnt −8, a Xenopus Wnt −1/ int −1-related gene responsive to mesoderm-inducing growth factors, may play a role in ventral mesodermal patterning during embryogenesis.
Development
111
,
1045
1055
Christian
J. L.
,
Olson
D. J.
,
Moon
R. T.
(
1992
).
Xwnt −8 modifies the character of mesoderm induced by bFGF in isolated Xenopus ectoderm.
EMBO J
11
,
33
41
Christian
J. L.
,
Moon
R. T.
(
1993
).
When cells take fate into their own hands: Differential competence to respond to inducing signals generates diversity in the embryonic mesoderm.
BioEssays
15
,
135
140
Dale
L.
,
Howes
G.
,
Price
B. M. J.
,
Smith
J. C.
(
1992
).
Bone morphogenetic protein 4: a ventralizing factor in early Xenopus development.
Development
115
,
573
585
Detrick
R. J.
,
Dickey
D.
,
Kintner
C. R.
(
1990
).
The effects of N-cadherin misexpression on morphogenesis in Xenopus embryos.
Neuron
4
,
493
506
Feinberg
A.
,
Vogelstein
B.
(
1984
).
A technique for radiolabelling DNA restriction endonuclease fragments to high specific activity.
Analyt. Biochem
137
,
266
267
Gavin
B. J.
,
McMahon
J. A.
,
McMahon
A. P.
(
1990
).
Expression of multiple novel Wnt −1/ int −1-related genes during fetal and adult mouse development.
Genes Dev
4
,
2319
2332
Green
J. B. A.
,
Howes
G.
,
Symes
K.
,
Cooke
J.
,
Smith
J. C.
(
1990
).
The biological effects of XTC-MIF: Quantiative comparison with Xenopus bFGF.
Development
108
,
173
183
Gurdon
J. B.
,
Wickens
M. P.
(
1983
).
The use of Xenopus oocytes for the expression of cloned genes.
Methods Enzymol
101
,
370
386
Harland
R. M.
(
1991
).
In situ hybridization: An improved whole-mount method for Xenopus embryos.
MethodsCell Biol
36
,
685
695
Jones
C. M.
,
Lyons
K. M.
,
Lapan
P. M.
,
Wright
C. V. E.
,
Hogan
B. L. M.
(
1992
).
BVR-4 (Bone morphogenetic protein-4) as a posterior-ventralizing factor in Xenopus mesoderm induction.
Development
115
,
639
647
Jue
S. F.
,
Bradley
R. S.
,
Rudnicki
J. A.
,
Varmus
H. E.
,
Brown
A. M. C.
(
1992
).
The mouse Wnt −1 gene can act via a paracrine mechanism in transformation of mammary epithelial cells.
Molec. Cell Biol
12
,
321
328
Kelly
G. M.
,
Eib
D. W.
,
Moon
R. T.
(
1991
).
Histological preparation of Xenopus laevis oocytes and embryos.
Methods Cell Biol
36
,
389
417
Kimelman
D.
,
Christian
J. L.
,
Moon
R. T.
(
1992
).
Synergistic principles of development: Overlapping patterning systems in Xenopus mesoderm induction.
Development
116
,
1
9
Kintner
C.
,
Brockes
J. P.
(
1984
).
Monoclonal antibodies to the cells of a regenerating limb.
J. Embryol. Exp. Morph
89
,
37
55
Klymkowsky
M. W.
,
Hanken
J.
(
1991
).
Whole mount staining of Xenopus and other vertebrates.
Methods Cell Biol
36
,
420
441
Krauss
S.
,
Korzh
V.
,
Fjose
A.
,
Johansen
T.
(
1992
).
Expression of four zebrafish wnt -related genes during embryogenesis.
Development
116
,
249
259
McMahon
A. P.
,
Moon
R. T.
(
1989
).
Ectopic expression of the proto-oncogene int −1 in Xenopus embryos leads to duplication of the embryonic axis.
Cell
58
,
1075
1084
McMahon
A. P.
,
Bradley
A.
(
1990
).
The Wnt −1 (int −1) proto-oncogene is required for development of a large region of the mouse brain.
Cell
62
,
1073
–.
Moody
S. A.
(
1987
).
Fates of the blastomeres of the 32-cell-stage Xenopus embryo.
Dev. Biol
122
,
300
319
Moon
R. T.
,
Christian
J. L.
(
1992
).
Competence modifiers synergize with growth factors during mesoderm induction and patterning in Xenopus.
Cell
71
,
708
712
Noordermeer
J.
,
Meijlink
F.
,
Verrijzer
P.
,
Rijsewijk
F.
,
Destree
O.
(
1989
).
Isolation of the Xenopus homolog of int −1/ wingless and expression during neurula stages of early development.
Nucl. Acids Res
17
,
11
18
Nusse
R.
,
Varmus
H. E.
(
1992
).
Wnt genes.
Cell
69
,
1073
1087
Olson
D. J.
,
Christian
J. L.
,
Moon
R. T.
(
1991
).
Effect of Wnt −1 and related proteins on gap junctional communication in Xenopus embryos.
Science
252
,
1173
1176
Papkoff
J.
,
Schryver
B.
(
1990
).
Secreted int −1 protein is associated with the cell surface.
Mol. Cell Biol
10
,
2723
2730
Rebagliati
M. R.
,
Weeks
D. L.
,
Harvey
R. P.
,
Melton
D. A.
(
1985
).
Identification and cloning of localized maternal RNAs from Xenopus eggs.
Cell
42
,
769
777
Rijsewijk
F.
,
Schuermann
M.
,
Wagenaar
E.
,
Parren
P.
,
Weigel
D.
,
Nusse
R.
(
1987
).
The Drosophila homolog of the mouse mammary oncogene int −1 is identical to the segment polarity gene wingless.
Cell
50
,
649
657
Sanger
F.
,
Nicklen
S.
,
Coulson
A. R.
(
1977
).
DNA sequencing with chain-terminating inhibitors.
Proc. Natl. Acad. Sci. USA
74
,
5463
5467
Smith
J. C.
,
Price
B. M. J.
,
Green
J. B. A.
,
Weigel
D.
,
Herrmann
B. G.
(
1991
).
Expression of a Xenopus homolog of Brachyury (T) is an immediate-early response to mesoderm induction.
Cell
67
,
79
87
Smith
W. C.
,
Harland
R. M.
(
1991
).
Injected Xwnt −8 RNA acts early in Xenopus embryos to promote formation of a vegetal dorsalizing center.
Cell
67
,
753
765
Sokol
S.
,
Christian
J. L.
,
Moon
R. T.
,
Melton
D. A.
(
1991
).
Injected Wnt RNA induces a complete body axis in Xenopus embryos.
Cell
67
,
741
752
Sokol
S.
,
Melton
D. A.
(
1991
).
Pre-existent pattern in Xenopus animal pole cells revealed by induction with activin.
Nature
351
,
409
411
Thomas
K. R.
,
Capecchi
M. R.
(
1990
).
Targeted disruption of the murine int −1 proto-oncogene resulting in severe abnormalities in midbrain and cerebellar development.
Nature
346
,
847
850
van den Heuvel
M.
,
Nusse
R.
,
Johnston
P.
,
Lawrence
P. A.
(
1989
).
Distribution of the wingless gene product in Drosophila embryos: A protein involved in cell-cell communication.
Cell
59
,
739
749
Whitman
M.
,
Melton
D. A.
(
1992
).
Involvement of p21ras in Xenopus mesoderm induction.
Nature
357
,
252
254
Wolda
S. L.
,
Moody
C. J.
,
Moon
R. T.
(
1993
).
Overlapping expression of Xwnt −3A and Xwnt −1 in neural tissue of Xenopus laevis embryos.
Dev. Biol
155
,
46
57
This content is only available via PDF.