In order to study anteroposterior neural patterning in Xenopus embryos, we have developed a novel assay using explants and tissue recombinants of early neural plate. We show, by using region-specific neural markers and lineage tracing, that posterior axial tissue induces midbrain and hindbrain fates from prospective forebrain. The growth factor bFGF mimics the effect of the posterior dorsal explant in that it (i) induces forebrain to express hindbrain markers, (ii) induces prospective hindbrain explants to make spinal cord, but not forebrain and midbrain, and (iii) induces posterior neural fate in ectodermal explants neuralized by the dominant negative activin receptor and follistatin without mesoderm induction. The competence of forebrain explants to respond to both posterior axial explants and bFGF is lost by neural groove stages. These findings demonstrate that posterior neural fate can be derived from anterior neural tissue, and identify a novel activity for the growth factor bFGF in neural patterning. Our observations suggest that full anteroposterior neural patterning may be achieved by caudalization of prospective anterior neural fate in the vertebrate embryo.

Reference

Basler
K.
,
Edlund
T.
,
Jessell
T. M.
,
Yamada
T.
(
1993
)
Control of cell pattern in the neural tube: regulation of cell differentiation by dorsalin-1, a novel TGFfamily member.
Cell
73
,
687
702
Bradley
L. C.
,
Snape
A.
,
Bhatt
S.
,
Wilkinson
D. G.
(
1992
)
The structure and expression of the XenopusKrox-20 gene: conserved and divergent patterns of expression in rhombomeres and neural crest.
Mech. Dev
40
,
73
84
Doniach
T.
(
1993
)
Planar and vertical induction of anteroposterior pattern during the development of the amphibian central nervous system.
J. Neurobiol
24
,
1256
1275
Eagleson
G. W.
,
Harris
W. A.
(
1989
)
Mapping of the presumptive brain regions in the neural plate of Xenopus laevis.
J. Neurobiol
21
,
427
440
Gardner
C. A.
,
Barald
K. F.
(
1991
)
The cellular environment controls the expression of engrailed -like protein in the cranial neuroepithelium of quail-chick chimeric embryos.
Development
113
,
1037
1048
Harland
R. M.
(
1991
)
In situ hybridization: an improved wholemount method for Xenopus embryos.
Methods in Cell Biology
36
Hemmati-Brivanlou
A.
,
Harland
R. M.
(
1989
).
Expression of an engrailed- related protein is induced in the anterior neural ectoderm of early Xenopus embryos.
Development
106
,
611
617
Hemmati-Brivanlou
A.
,
Stewart
R.
,
Harland
R. M.
(
1990
)
Region-specific neural induction of an engrailed protein by anterior notochord in Xenopus.
Science
250
,
800
802
Hemmati-Brivanlou
A.
,
de la Torre
J. R.
,
Holt
C.
,
Harland
R. M.
(
1991
)
Cephalic expression and molecular charaterization of Xenopus En-2.
Development
111
,
715
724
Hemmati-Brivanlou
A.
,
Melton
D. A.
(
1992
)
A truncated activin receptor dominately inhibits mesoderm induction and formation of axial structures in Xenopus embryos.
Nature
359
,
609
614
Hemmati-Brivanlou
A.
,
Melton
D. A.
(
1994
)
Inhibition of activin receptor signaling promotes neuralization in Xenopus.
Cell
77
,
273
281
Hemmati-Brivanlou
A.
,
Kelly
O. G.
,
Melton
D. A.
(
1994
)
Follistatin, an antagonist of activin, is expressed in the Spemman organizer and displays direct neuralizing activity.
Cell
77
,
283
295
Isaacs
H. V.
,
Tannahill
D.
,
Slack
J. M. W.
(
1992
)
Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification.
Development
114
,
711
720
Kimelman
D.
,
Maas
A.
(
1992
)
Induction of dorsal and ventral mesoderm by ectopically expressed Xenopus basic fibroblast growth factor.
Development
114
,
261
269
Kintner
C.R.
,
Melton
D.A.
(
1987
)
Expression of Xenopus N-CAM RNA in ectoderm is an early response to neural induction.
Development
99
,
311
325
Krieg
P.
,
Varnum
S.
,
Wormington
M.
,
Melton
D. A.
(
1989
)
The mRNA encoding elongation factor 1a (EF1a) is a major transcript at the mid blastula transition in Xenopus.
Dev. Biol
133
,
93
100
Lamb
T. M.
,
Knecht
A. K.
,
Smith
W. C.
,
Stachel
S. E.
,
Economides
A.N.
,
Stahl
N.
,
Yancopolous
G. D.
,
Harland
R. M.
(
1993
)
Neural induction by the secreted polypeptide noggin.
Science
262
,
713
718
Mangold
O.
(
1933
)
Uber die Induktionsfahigkeit der verschiedenen Bezirke der Neurula von Urodelen.
Naturwissenschaften
21
,
761
766
Martinez
S.
,
Alvarado-Mallart
R.-M.
(
1990
)
Expression of the homeobox chick- en gene in chick/quail chimeras with inverted mes-metencephalic grafts.
Dev. Biol
139
,
432
436
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
1085
McMahon
A. P.
(
1993
)
Cell signalling in induction and anterior-posterior patterning of the vertebrate central nervous system.
Curr. Opin. Neurobiol
3
,
4
7
Nieuwkoop
P. D.
,
Boterenbrood
E. C.
,
Kremer
A.
,
Bloesma
F. F. S. N.
,
Hoessels
E. L. M. J.
,
Meyer
G.
,
Verheyen
F. J.
(
1952
)
Activation and organization of the central nervous system in amphibians.
J. Exp. Zool
120
,
1
108
Nieuwkoop
P. D.
,
Nigtevecht
G. V.
(
1954
)
Neural activation and transformation in explants of competent ectoderm under the influence of fragments of anterior notochord in urodeles.
J. Embryol. Exp. Morph
2
,
175
193
Ruiz i Altaba
A.
(
1993
)
Induction and axial patterning of the neural plate: planar and vertical signals.
J. Neurobiol
24
,
1276
1304
Saha
M. S.
,
Grainger
R. M.
(
1992
)
A labile period in the determination of the anterior-posterior axis during early neural development in Xenopus.
Neuron
8
,
1003
14
Saxen
L.
,
Toivonen
S.
(
1961
)
The two-gradient hypothesis of primary neural induction. The combined effects of two types of inductors mixed at different ratios.
J. Embryol. Exp. Morph
9
,
514
533
Sharpe
C. R.
,
Gurdon
J. B.
(
1990
)
The induction of anterior and posterior neural genes in Xenopus laevis.
Development
109
,
765
774
Sharpe
C. R.
(
1991
)
Retinoic acid can mimic endogenous signals involved in transformation of the Xenopus laevis nervous system.
Neuron
7
,
239
247
Sive
H. L.
,
Hattori
K.
,
Weintraub
H.
(
1989
)
Progressive detemination during formation of the anteroposterior axis of Xenopuslaevis.
Cell
58
,
171
180
Sive
H. L.
,
Draper
B. W.
,
Harland
R. M.
,
Weintraub
H.
(
1990
)
Identification of a retinoic acid sensitive period during primary axis formation in Xenopus laevis.
Genes Dev
4
,
932
942
Song
J.
,
Slack
J. M. W.
(
1994
)
Spatial and temporal expression of basic fibroblast growth factor (FGF-2) mRNA and protein in early Xenopus development.
Mech. Dev
48
,
141
151
Stutz
F.
,
Spohr
G.
(
1986
)
Isolation and characterization of sarcomeric actin genes expressed in Xenopus laevis embryogenesis.
J. Mol. Biol
187
,
349
361
Tannahill
D.
,
Isaacs
H. V.
,
Close
M. J.
,
Peters
G.
,
Slack
J. M. W.
(
1992
)
Developmental expression of the Xenopusint-2 (FGF-3) gene: activation by mesodermal and neural induction.
Development
115
,
695
702
Thomsen
G. H.
,
Melton
D. A.
(
1993
)
Processed Vg1 protein is an axial mesoderm inducer in Xenopus.
Cell
74
,
433
441
Toivonen
S.
,
Saxen
L.
(
1955
)
The simultaneous inducing action of liver and bone-marrow of the guinea-pig in implantation and explantation experiments with embryos of Trituris.
Exp. Cell Res
3
,
346
357
Toivonen
S.
,
Saxen
L.
(
1968
)
Morphogenetic interaction of presumptive neural and mesodermal cells mixed in different ratios.
Science
159
,
539
40
Wilson
P. A.
,
Melton
D. A.
(
1994
)
Mesodermal patterning by an inducer gradient depends on secondary cell-cell communication.
Curr. Biol
4
,
676
686
Wright
C. V. E.
,
Morita
E. A.
,
Wilkin
D. J.
,
DeRobertis
E. M.
(
1990
)
The Xenopus XlHbox6 homeo protein, a marker of posterior neural induction, is expressed in proliferating neurons.
Development
109
,
225
234
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