1 Laboratory of Molecular Genetics, National Institute of Child Health and Human
Development, National Institutes of Health, Bethesda, MD 20892, USA
2 Department of Biology, University of Pennsylvania, Philadelphia, PA 19104,
USA
* Author for correspondence (e-mail: idawid{at}nih.gov).
Accepted 4 March 2004
![]() |
SUMMARY |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: MAPK phosphatase, Dorsoventral polarity, Midblastula transition
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
During embryogenesis, FGFs are crucial in the specification of limb
outgrowth, the establishment of the isthmic organizer and the patterning of
the hindbrain, and further have a role in cell proliferation and survival
(Maves et al., 2002;
Reifers et al., 1998
;
Sun et al., 2002
;
Trumpp et al., 1999
;
Walshe et al., 2002
). FGF
proteins may act in a redundant manner so that the simultaneous inactivation
of multiple FGF proteins has revealed overlapping functions for these secreted
ligands in several vertebrate species. For example, both FGF3 and FGF8 have
been shown to be crucial in the formation of the zebrafish otic placode and
ventral thalamus (Leger and Brand,
2002
; Maroon et al.,
2002
; Walshe and Mason,
2003
). Furthermore, temporal inactivation of FGFs has revealed
specific novel functions for FGF3 during the development of the posterior
pharyngeal cartilage of the zebrafish ventral head skeleton
(David et al., 2002
).
As the FGF signaling pathway is important for a multitude of developmental
processes, tight regulation of its signal intensity and duration is crucial
(Evans and Hemmings, 1998;
Niehrs and Meinhardt, 2002
).
Several modulators of the FGF pathway have been identified, including the
cytosolic proteins Sprouty and Spred, and the transmembrane protein SEF, all
of which function to ensure that proper signaling levels are achieved during
development (Fürthauer et al.,
2002
; Hacohen et al.,
1998
; Tsang et al.,
2002
; Wakioka et al.,
2001
). Sprouty and Spred are general inhibitors of RTK signaling
working at the level of RAS/MAPK signaling
(Hanafusa et al., 2002
;
Wakioka et al., 2001
). SEF can
inhibit both the RAS/MAPK and PI3K branches of the FGF pathway but does not
affect pathways initiated by other ligands
(Fürthauer et al., 2002
;
Kovalenko et al., 2003
;
Tsang et al., 2002
). Recently,
mouse, chick and Drosophila MKP3s have been shown to be involved in
attenuating RAS/MAPK signaling (Dickinson
et al., 2002
; Eblaghie et al.,
2003
; Kawakami et al.,
2003
; Klock and Herrmann,
2002
; Rintelen et al.,
2003
). The role of MKP3 appears to be limited to FGF/RAS/MAPK
signaling in the developing chick embryo as mkp3 expression coincides
with regions of FGF signaling activity. MKP3 is thus another negative feedback
inhibitor of the FGF pathway in the embryo
(Eblaghie et al., 2003
;
Kawakami et al., 2003
). Two
distinct domains are characteristic of MKP3 proteins, the N-terminal region,
which contains a high-affinity ERK/MAPK binding domain, and the C-terminal
domain, which constitutes a dual specificity phosphatase
(Stewart et al., 1999
;
Zhang et al., 2003
;
Zhao and Zhang, 2001
). MKP3
negatively regulates the MAPK cascade through dephosphorylation of the
di-phosphorylated activated MAPK1 and MAPK2 (p42/p44) proteins. Upon binding
of phosphorylated MAPKs to the MAPK-binding domain in MKP3, a conformational
activation of the C-terminal phosphatase domain is achieved, leading to the
inactivation of MAPKs (Camps et al.,
1998
; Fjeld et al.,
2000
; Zhao and Zhang,
2001
). Thus, the FGF pathway not only induces the transcriptional
activation of feedback inhibitors such as sprouty (spry),
sef and mkp3, but through the activation of MAPKs, MKP3
protein is also catalytically stimulated to dampen FGF signaling
(Camps et al., 1998
;
Zhao and Zhang, 2001
).
In this study, we report the identification of zebrafish mkp3 from
a random in situ screen that showed similar expression to fgf3, fgf8,
the Ets transcription factors erm and pea3, and the FGF
inhibitors sef and spry
(Fürthauer et al., 2002;
Fürthauer et al., 2001
;
Kudoh et al., 2001
;
Raible and Brand, 2001
;
Tsang et al., 2002
). We
determined that MKP3 is a negative feedback regulator of FGF signaling in the
zebrafish embryo as it is in mammalian cells, and we show by loss-of-function
and gain-of-function experiments that MKP3 is involved in axial patterning.
Furthermore, we show that mkp3 expression is initiated by maternal
ß-catenin activity prior to any detectable FGF/RAS/MAPK signaling. These
findings highlight the importance of tight regulation of FGF signal
transduction in the early embryo.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Zebrafish fgf3 and fgf8 used in this study were also
cloned from the in situ screen (Kudoh et
al., 2001). The DNAkt expression construct was generated by
subcloning DNAkt cDNA into pCS2+ (Kohn et
al., 1996
).
Zebrafish maintenance, RNA injections and in situ hybridization
These procedures were performed as described previously
(Tsang et al., 2000) with the
following modifications for RNA injections. Wild-type zebrafish embryos were
injected with mkp3, HA::mkp3 and mkp3::C292S at the 1- to
4-cell stage with 250 pg and 500 pg RNA. To determine the regulation of
mkp3 expression, wild-type zebrafish embryos were injected with RNA
encoding fgf8 (5 pg), XFD (250 pg), DNRas (250 pg), MKP3 (500 pg),
DNAkt (500 pg), ß-cateninS/A mutant (200 pg) and
N-tcf3 (250 pg).
ichabod mutant embryos were injected with 10 pg or 1 pg
fgf3; 10 pg, 1 pg or 0.1 pg fgf8; 50 pg ß-catenin; or
50 pg nß-galactosidase RNA at the 1-cell stage.
Antisense morpholino oligo injections
Morpholino oligos (MO) were obtained from Genetools as follows: mkp3MO
sequence, 5'-GCACGGGTTTGAACTTATACGAGCAT-3'; ContMO sequence,
5'-CCTCTTACCTCAGTTACAATTTATA-3'; and mkp3misMO sequence,
5'-GCtCGcGTTTGAtCTTATCcATgAT-3'.
mkp3MO and mkp3misMO (5 nl) was injected into 2- to 8-cell stage embryos at concentrations ranging from 2-4 mg ml-1, while ContMO was injected at 4 mg ml-1.
Animal cap assay
Xenopus laevis 2-cell stage embryos were injected with activated
RAS RNA at 20 pg and mkp3 or mkp3::C292S at 500 pg into each
blastomere, as indicated (Whitman and
Melton, 1992). Animal caps were dissected at stage 8.5 and
cultured until stage 10.5. RNA was isolated from 24 caps for each experiment,
and analyzed by RT-PCR as described previously
(Tsang et al., 2002
)
RT-PCR
Zebrafish embryos were fixed and total RNA was isolated from the indicated
stages. Total RNA (2 µg) was reverse transcribed with Superscript II
Reverse Transcriptase (Invitrogen) and amplified with the following primers:
Histone H4, 5'-CACGAAACCCGCCATCCGTCG-3' (forward) and
5'-GTACAGAGTGCGTCCCTGCCG-3' (reverse), 25 cycles; ß-actin,
5'-GTATCCTGACCCTGAAGTACCC-3' (forward) and
R:5'-AGCACAGCCTGGATGGCAACG-3' (reverse), 25 cycles; mkp3,
5'-CGTTCAGAGGGGTTGTCCG-3' (forward) and
R:5'-CTTCCCTGAACAGGAGACCC-3' (reverse), 27 cycles.
Cycles conditions were 94°C for 1 minute; 56°C for 1 minute; 72°C for 1 minute.
Immunohistochemical staining and western blotting
Zebrafish embryos were fixed with 4% paraformaldehyde followed by Methanol
storage. Embryos were treated with acetone for 10 minutes at -20°C and
re-hydrated with a series of PBS/0.1% Tween:Ethanol at room temperature.
Embryos were incubated overnight with 1:10,000 anti di-phospho ERK antibodies
(Sigma), followed by washes with PBS/0.1% Tween. Anti-mouse IgG-HRP
(Calbiochem) was incubated with the embryos at a 1:5000 dilution for 4 hours,
and embryos were washed overnight. Diaminobenzidine staining was performed as
described (Westerfied, 1993).
Western blotting was performed as stated previously
(Habas et al., 2001
). Mouse
anti phospho-ERK (Sigma) antibodies were used at 1:500 and Rabbit anti-ERK
(Promega) at 1:1000 dilutions.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
Maternal ß-catenin activity initiates mkp3 expression
The initiation of mkp3 expression was remarkable in that
transcripts were detected very soon after MBT at the high stage, prior to any
known FGF activity in the embryo (Fig.
2B). We confirmed by RT-PCR that mkp3 is activated at the
high stage, whereas no maternal RNA was detected
(Fig. 3A). To define the
temporal activation of FGF signaling we revisited the issue of the initial
expression of fgf3 and fgf8. Both genes exhibited weak
expression at the oblong stage (3.7 hpf), while mkp3 was detected at
the high stage at 3.3 hpf (compare Fig.
2B with Fig. 3C,D).
To define the timing of FGF activity in the early embryo, as opposed to gene
expression, we used specific antibodies to detect the presence of
phosphorylated MAPK (MAPK-p). Through western blotting and immunohistochemical
techniques, we determined the onset of FGF activity in the zebrafish embryo at
the oblong stage within the prospective dorsal region
(Fig. 3B,E,F). This timing is
similar to the observations in the early Xenopus embryo, in which FGF
signaling is activated after the MBT and before the onset of gastrulation
(Schohl and Fagotto, 2002).
These results suggest that the initiation of mkp3 expression does not
depend on FGF activity but rather is elicited by a maternal signal.
To confirm that this is the case, we injected XFD to block FGF signaling,
and examined embryos fixed at the high and at later stages for the initiation
in mkp3 expression. Embryos injected with XFD and fixed at the high
stage exhibited normal mkp3 expression
(Fig. 3G,H), supporting the
view that initiation of this expression is independent of FGF signaling. By
contrast, XFD-injected embryos examined at the sphere or dome stage showed a
marked reduction in mkp3 expression
(Fig. 2J,K;
Fig. 3I,J); thus, the
FGF-independent period of mkp3 expression is quite short in the
post-MBT zebrafish embryo. As mkp3 is activated in the region of the
embryo that will give rise to the organizer, the ß-catenin signal, which
is known to be essential for organizer formation, is thought to be involved in
this event (Kelly et al.,
2000; Wylie et al.,
1996
).
To test this prediction, we used several approaches. First, we activated
ß-catenin signaling by treating early embryos with lithium chloride
(LiCl) (Klein and Melton,
1996). LiCl-treated embryos showed a strong expansion of
mkp3 expression at the high stage, in agreement with the prediction
that stabilization of ß-catenin activates mkp3
(Fig. 3L). Likewise, injection
of an activated form of ß-catenin (ß-catenin S>A; this form
cannot be phosphorylated and targeted for degradation) led to ectopic
activation of mkp3 (Fig.
3M) (Liu et al.,
1999
). By contrast, a dominant-negative form of Tcf3
(
N-tcf3), the transcriptional partner of ß-catenin, could suppress
the initiation of mkp3 expression
(Fig. 3N)
(Kim et al., 2000
;
Molenaar et al., 1996
).
Finally, we used two mutant zebrafish lines, ichabod (ich)
and bozozok (boz), to confirm that mkp3 expression
was initiated by the activity of maternal ß-catenin
(Fekany et al., 1999
;
Kelly et al., 2000
;
Koos and Ho, 1999
). In the
maternal ventralized mutant ich, which exhibits a failure in the
nuclear accumulation of ß-catenin
(Kelly et al., 2000
),
mkp3 expression was absent within the dorsal region of the embryo at
blastula stages (Fig. 3O,P).
Activation of mkp3 through ß-catenin and FGF are independent
events, as injection of fgf8 RNA could induce the expression of
mkp3 in the ich mutant embryo
(Fig. 3Q). Mkp3
appears to be a direct target of ß-catenin, as its activation did not
require boz function. In the boz mutant, the major
ß-catenin target Boz/Dha/Nieuwkoid, a homeobox transcription factor, is
not functional, leading to deficiency of organizer formation
(Fekany et al., 1999
;
Koos and Ho, 1999
). However,
initiation of mkp3 expression did take place in the boz
mutant with normal timing and intensity
(Fig. 3R), suggesting that it
is a direct consequence of ß-catenin activity. These experiments suggest
that mkp3, which during most stages of development is a target of FGF
signaling, is initially activated through the ß-catenin signaling
pathway.
Functional role for MKP3 during embryogenesis
To determine the function of MKP3 during development, we engineered
expression constructs for the wild type protein and a phosphatase mutant
version, MKP3::C292S (Fig. 4A).
We assayed the activity of these constructs in Xenopus animal cap
explants to determine if MKP3 could block MAPK signaling. Overexpression of
wild-type mkp3 could inhibit Xenopus Brachyury
(Xbra) mRNA induction by an activated form of RAS
(Fig. 4B). The co-expression of
mkp3::C292S with activated RAS did not alter the induction of
Xbra, suggesting that this mutant construct was functionally inactive
in this assay, similar to a previous report
(Mason et al., 1996). We next
determined whether ectopic expression of mkp3 could repress the FGF
target genes sef and spry4 in the zebrafish embryo.
Expression of both sef and spry4 were diminished in
mkp3 RNA-injected embryos at the shield stage
(Fig. 4D,H), while sef
and spry4 were unaffected or in some instances upregulated in
mkp3::C292S-injected embryos, suggesting that mkp3::C292S
can function in a dominant-negative manner in the zebrafish embryo
(Fig. 4F,J). These experiments
indicate that ectopic expression of mkp3 can suppress FGF signaling
in the early embryo.
|
|
|
|
|
|
|
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
It has been documented that Mkp3 expression can also be induced
directly by retinoic acid (RA) signaling in Xenopus
(Mason et al., 1996;
Moreno and Kintner, 2004
). It
has even been postulated that this RA regulation is key to controlling FGF
signaling during somite development in Xenopus through the activation
of Mkp3 expression (Moreno and
Kintner, 2004
). It is possible that activation of the RAS/MAPK
pathway by members of the receptor tyrosine kinase family other than FGFR can
also induce mkp3 expression. During early development, it is clear
that FGFs regulate mkp3 expression, but ligands belonging to the
platelet derived growth factor (PDGF) or the insulin growth factor (IGF)
families might also contribute to the regulation of mkp3 expression,
as they too are expressed early and can activate RAS/MAPK signaling in the
embryo (Ayaso et al., 2002
;
Liu et al., 2002
;
Mercola et al., 1988
;
Pera et al., 2003
;
Pera et al., 2001
). However,
it is unlikely that PDGF or IGF contribute to the regulation of mkp3
expression in the embryo, as both factors are either more widely expressed or
too restricted when compared with the expression domains of mkp3
(Ayaso et al., 2002
;
Liu et al., 2002
).
Disruption of the initial RAS/MAPK signal through the ectopic expression of
mkp3 results in ventralized embryos, while knock down of MKP3 protein
results in the opposite phenotype. The availability of the ich mutant
has allowed us to determine that the initial FGF signal is crucial for axial
patterning, while the later expression of FGF genes within the margin is
responsible for mesoderm induction and maintenance. As FGF proteins can also
activate other signaling pathways besides RAS/MAPK, such as the PI3K and the
PLC cascades, the question still remains as to whether these pathways
are also required for establishing the dorsal polarity of the embryo. Studies
in Xenopus have shown that the PI3K pathway works in parallel with
the RAS/MAPK pathway in mesoderm induction
(Carballada et al., 2001
). This
is also most probably the situation in zebrafish, as the ventralized
phenotypes derived from ectopic expression of MKP3 were not fully penetrant
(see Table 1). Studies looking
at the role of PI3K in zebrafish gastrulation movements have revealed that
early ectopic expression of dominant-negative PI3K resulted in axial
patterning defects (Montero et al.,
2003
). Finally, a PLC
zebrafish mutant has been isolated
and characterized and shown to be defective in the formation of intersegmental
blood vessels (Lawson et al.,
2003
). There was no obvious early dorsoventral patterning
phenotype attributed to the PLC
mutant and this may be explained by the
fact that PLC
is found as a maternal transcript (N. D. Lawson,
unpublished). Future studies may reveal whether PLC
is also crucial in
the FGF pathway for axial patterning.
How FGFs can regulate early dorsoventral patterning is not completely
understood. One observation is that FGFs can directly suppress the initiation
of bmp4 expression in the early embryo
(Fürthauer et al., 1997).
Similarly, we show that ectopic expression of mkp3 has the opposite
effect in that the expression of bmp4 was expanded towards the dorsal
region of the embryo. In addition, FGFs can induce the expression of the BMP
inhibitor chd (Koshida et al.,
2002
; Mitchell and Sheets,
2001
), suppressing the activity of any BMP protein that is
generated. This provides further protection of the dorsal region from the
ventralizing effects of secreted BMPs. We show that modulating the activity of
MKP3 within the early zebrafish embryo prior to gastrulation alters the
expression of chd. Recently, it has shown that FGF acting through the
RAS/MAPK pathway can directly inactivate SMAD1 function. As SMAD1 is one of
the main molecules responsible for propagating the BMP signal, this explains
how FGFs can directly suppress BMP activity
(Kretzschmar et al., 1997
;
Pera et al., 2003
;
Sater et al., 2003
). Thus, we
support the view that FGFs have a two-pronged effect in the suppression of the
ventralizing BMPs. FGFs appear to act in concert with boz to directly
suppress the initiation of Bmp gene expression within the future dorsal region
of the embryo. This provides a basis for maintaining a bias for organizer
formation, while the second effect of dorsal FGF activity is to activate the
expression of chd.
Maternal ß-catenin activity and activation of FGF signaling in the early embryo
Observations in Xenopus point to the initiation of XFgf3
expression within the prospective mesodermal region by maternal ß-catenin
activity, and suggest that this expression is a key requirement in mesoderm
induction and maintenance (Schohl and
Fagotto, 2003). We find that the expression of fgf3 is
lost in the ich mutant, thus suggesting a possible conservation in
the initiation of the FGF signaling cascade in the early embryo between
zebrafish and Xenopus. The difference is that the initial
fgf3 expression in the zebrafish is limited to the future dorsal
region of the embryo, while later it is localized more widely within the
margin. It is this difference in the initial expression that may account for
the difference in the activities of early FGF signaling between the two
species. In the zebrafish, ectopic expression of FGFs can dorsalize the
embryo, while in Xenopus ectopic FGFs expand mesodermal tissue
(Kimelman and Kirschner, 1987
;
Slack et al., 1987
;
Fürthuer et al., 1997). Mutagenesis screens in zebrafish so far have only
identified ace/fgf8 and ikarus/fgf24 as mutations within the
FGF pathway, and these mutations do not have defects in dorsal/ventral
patterning (Reifers et al.,
1998
; Draper et al.,
2003
; Fischer et al.,
2003
), suggesting that the FGF ligands act redundantly.
Although MKP3 acts as a feedback modulator of the RAS/MAPK pathway in most cell types and developmental stages, the maternal ß-catenin pathway induces the initial mkp3 expression prior to the time when the FGF/MAPK signal arises in the embryo. It is likely that the activity of maternal ß-catenin is responsible for the initiation of the entire FGF signaling pathway, including the activation of FGF genes and the negative feedback modulator mkp3. We propose that mkp3 induction is direct, based on the following observations: (1) expression of mkp3 is unchanged in boz mutant embryos; (2) the presence of multiple putative TCF3/LEF1 sites, the obligate DNA binding co-factors for ß-catenin, in the 5' region of the mkp3 gene (M.T., unpublished); and (3) the timing of the initial expression of mkp3, which is ahead of the earliest MAPK activation in the zebrafish embryo. Thus, we surmise that the requirement for tight regulation of FGF signaling makes it necessary to have the feedback regulator MKP3 in place before the initiation of any FGF signal itself arises in development. This need for precise regulation emphasizes the profound effect that FGF signaling has on specification of axial polarity in the early embryo.
![]() |
ACKNOWLEDGMENTS |
---|
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Amaya, E., Musci, T. J. and Kirschner, M. W. (1991). Expression of a dominant negative mutant of the FGF receptor disrupts mesoderm formation in Xenopus embryos. Cell 66,257 -270.[Medline]
Aoki, M., Batista, O., Bellacosa, A., Tsichlis, P. and Vogt, P.
K. (1998). The akt kinase: molecular determinants of
oncogenicity. Proc. Natl. Acad. Sci. USA
95,14950
-14955.
Ayaso, E., Nolan, C. M. and Byrnes, L. (2002). Zebrafish insulin-like growth factor-I receptor: molecular cloning and developmental expression. Mol. Cell. Endocrinol. 191,137 -148.[CrossRef][Medline]
Camps, M., Nichols, A. and Arkinstall, S.
(2000). Dual specificity phosphatases: a gene family for control
of MAP kinase function. FASEB J.
14, 6-16.
Camps, M., Nichols, A., Gillieron, C., Antonsson, B., Muda, M.,
Chabert, C., Boschert, U. and Arkinstall, S. (1998).
Catalytic activation of the phosphatase MKP-3 by ERK2 mitogen-activated
protein kinase. Science
280,1262
-1265.
Carballada, R., Yasuo, H. and Lemaire, P.
(2001). Phosphatidylinositol-3 kinase acts in parallel to the ERK
MAP kinase in the FGF pathway during Xenopus mesoderm induction.
Development 128,35
-44.
David, N. B., Saint-Etienne, L., Tsang, M., Schilling, T. F. and
Rosa, F. M. (2002). Requirement for endoderm and FGF3 in
ventral head skeleton formation. Development
129,4457
-4468.
Dickinson, R. J., Eblaghie, M. C., Keyse, S. M. and Morriss-Kay, G. M. (2002). Expression of the ERK-specific MAP kinase phosphatase PYST1/MKP3 in mouse embryos during morphogenesis and early organogenesis. Mech. Dev. 113,193 -196.[CrossRef][Medline]
Draper, B. W., Stock, D. W. and Kimmel, C. B.
(2003). Zebrafish fgf24 functions with fgf8 to promote posterior
mesodermal development. Development
130,4639
-4654.
Eblaghie, M. C., Lunn, J. S., Dickinson, R. J., Munsterberg, A. E., Sanz-Ezquerro, J. J., Farrell, E. R., Mathers, J., Keyse, S. M., Storey, K. and Tickle, C. (2003). Negative feedback regulation of FGF signaling levels by Pyst1/MKP3 in chick embryos. Curr. Biol. 13,1009 -1018.[CrossRef][Medline]
Evans, D. R. and Hemmings, B. A. (1998). Signal transduction. What goes up must come down. Nature 394, 23-24.[CrossRef][Medline]
Farooq, A., Chaturvedi, G., Mujtaba, S., Plotnikova, O., Zeng, L., Dhalluin, C., Ashton, R. and Zhou, M. M. (2001). Solution structure of ERK2 binding domain of MAPK phosphatase MKP-3: structural insights into MKP-3 activation by ERK2. Mol. Cell 7, 387-399.[Medline]
Fekany, K., Yamanaka, Y., Leung, T., Sirotkin, H. I.,
Topczewski, J., Gates, M. A., Hibi, M., Renucci, A., Stemple, D., Radbill, A.
et al. (1999). The zebrafish bozozok locus encodes Dharma, a
homeodomain protein essential for induction of gastrula organizer and
dorsoanterior embryonic structures. Development
126,1427
-1438.
Fischer, S., Draper, B. W. and Neumann, C. J.
(2003). The zebrafish fgf24 mutant identifies an additional level
of Fgf signaling involved in vertebrate forelimb initiation.
Development 130,3515
-3524.
Fjeld, C. C., Rice, A. E., Kim, Y., Gee, K. R. and Denu, J.
M. (2000). Mechanistic basis for catalytic activation of
mitogen-activated protein kinase phosphatase 3 by extracellular
signal-regulated kinase. J. Biol. Chem.
275,6749
-6757.
Fujii, R., Yamashita, S., Hibi, M. and Hirano, T.
(2000). Asymmetric p38 activation in zebrafish: its possible role
in symmetric and synchronous cleavage. J. Cell Biol.
150,1335
-1348.
Fürthauer, M., Thisse, C. and Thisse, B.
(1997). A role for FGF-8 in the dorsoventral patterning of the
zebrafish gastrula. Development
124,4253
-4264.
Fürthauer, M., Reifers, F., Brand, M., Thisse, B. and Thisse, C. (2001). sprouty4 acts in vivo as a feedback-induced antagonist of FGF signaling in zebrafish. Development 128,2175 -2186.[Medline]
Fürthauer, M., Lin, W., Ang, S. L., Thisse, B. and Thisse, C. (2002). Sef is a feedback-induced antagonist of Ras/MAPK-mediated FGF signalling. Nat. Cell Biol. 4, 170-174.[CrossRef][Medline]
Groom, L. A., Sneddon, A. A., Alessi, D. R., Dowd, S. and Keyse, S. M. (1996). Differential regulation of the MAP, SAP and RK/p38 kinases by Pyst1, a novel cytosolic dual-specificity phosphatase. EMBO J. 15,3621 -3632.[Abstract]
Habas, R., Kato, Y. and He, X. (2001). Wnt/Frizzled activation of Rho regulates vertebrate gastrulation and requires a novel Formin homology protein Daam1. Cell 107,843 -854.[CrossRef][Medline]
Hacohen, N., Kramer, S., Sutherland, D., Hiromi, Y. and Krasnow, M. A. (1998). sprouty encodes a novel antagonist of FGF signaling that patterns apical branching of the Drosophila airways. Cell 92,253 -263.[Medline]
Hanafusa, H., Torii, S., Yasunaga, T. and Nishida, E. (2002). Sprouty1 and Sprouty2 provide a control mechanism for the Ras/MAPK signalling pathway. Nat. Cell Biol. 4, 850-858.[CrossRef][Medline]
Jiang, B. H., Zheng, J. Z., Aoki, M. and Vogt, P. K.
(2000). Phosphatidylinositol 3-kinase signaling mediates
angiogenesis and expression of vascular endothelial growth factor in
endothelial cells. Proc. Natl. Acad. Sci. USA
97,1749
-1753.
Kawahara, A., Wilm, T., Solnica-Krezel, L. and Dawid, I. B. (2000). Functional interaction of vega2 and goosecoid homeobox genes in zebrafish. Genesis 28, 58-67.[CrossRef][Medline]
Kawakami, Y., Rodriguez-Leon, J., Koth, C. M., Buscher, D., Itoh, T., Raya, A., Ng, J. K., Esteban, C. R., Takahashi, S., Henrique, D. et al. (2003). MKP3 mediates the cellular response to FGF8 signalling in the vertebrate limb. Nat. Cell Biol. 5, 513-519.[CrossRef][Medline]
Kelly, C., Chin, A. J., Leatherman, J. L., Kozlowski, D. J. and
Weinberg, E. S. (2000). Maternally controlled
(beta)-catenin-mediated signaling is required for organizer formation in the
zebrafish. Development
127,3899
-3911.
Keyse, S. M. (2000). Protein phosphatases and the regulation of mitogen-activated protein kinase signalling. Curr. Opin. Cell Biol. 12, 186-92.[CrossRef][Medline]
Kim, C. H., Oda, T., Itoh, M., Jiang, D., Artinger, K. B., Chandrasekharappa, S. C., Driever, W. and Chitnis, A. B. (2000). Repressor activity of Headless/Tcf3 is essential for vertebrate head formation. Nature 407,913 -916.[CrossRef][Medline]
Kimelman, D. and Kirschner, M. (1987). Synergistic induction of mesoderm by FGF and TGF-beta and the identification of an mRNA coding for FGF in the early Xenopus embryo. Cell 51,869 -877.[Medline]
Klein, P. S. and Melton, D. A. (1996). A
molecular mechanism for the effect of lithium on development. Proc.
Natl. Acad. Sci. USA 93,8455
-8459.
Klock, A. and Herrmann, B. G. (2002). Cloning and expression of the mouse dual-specificity mitogen-activated protein (MAP) kinase phosphatase Mkp3 during mouse embryogenesis. Mech. Dev. 116,243 -247.[CrossRef][Medline]
Kohn, A. D., Takeuchi, F. and Roth, R. A.
(1996). Akt, a pleckstrin homology domain containing kinase, is
activated primarily by phosphorylation. J. Biol. Chem.
271,21920
-21926.
Koos, D. S. and Ho, R. K. (1999). The nieuwkoid/dharma homeobox gene is essential for bmp2b repression in the zebrafish pregastrula. Dev. Biol. 215,190 -207.[CrossRef][Medline]
Koshida, S., Shinya, M., Nikaido, M., Ueno, N., Schulte-Merker, S., Kuroiwa, A. and Takeda, H. (2002). Inhibition of BMP activity by the FGF signal promotes posterior neural development in zebrafish. Dev. Biol. 244,9 -20.[CrossRef][Medline]
Kovalenko, D., Yang, X., Nadeau, R. J., Harkins, L. K. and
Friesel, R. (2003). Sef inhibits fibroblast growth factor
signaling by inhibiting FGFR1 tyrosine phosphorylation and subsequent ERK
activation. J. Biol. Chem.
278,14087
-14091.
Kretzschmar, M., Doody, J. and Massague, J. (1997). Opposing BMP and EGF signalling pathways converge on the TGF-beta family mediator Smad1. Nature 389,618 -622.[CrossRef][Medline]
Kudoh, T., Tsang, M., Hukriede, N. A., Chen, X., Dedekian, M.,
Clarke, C. J., Kiang, A., Schultz, S., Epstein, J. A., Toyama, R. et al.
(2001). A gene expression screen in zebrafish embryogenesis.
Genome Res. 11,1979
-1987.
Lawson, N. D., Mugford, J. W., Diamond, B. A. and Weinstein, B.
M. (2003). phospholipase C gamma-1 is required downstream of
vascular endothelial growth factor during arterial development.
Genes Dev. 17,1346
-1351.
Leger, S. and Brand, M. (2002). Fgf8 and Fgf3 are required for zebrafish ear placode induction, maintenance and inner ear patterning. Mech. Dev. 119,91 -108.[CrossRef][Medline]
Liu, C., Kato, Y., Zhang, Z., Do, V. M., Yankner, B. A. and He,
X. (1999). beta-Trcp couples beta-catenin
phosphorylation-degradation and regulates Xenopus axis formation.
Proc. Natl. Acad. Sci. USA
96,6273
-6278.
Liu, L., Korzh, V., Balasubramaniyan, N. V., Ekker, M. and Ge, R. (2002). Platelet-derived growth factor A (pdgf-a) expression during zebrafish embryonic development. Dev. Genes Evol. 212,298 -301.[CrossRef][Medline]
Lun, K. and Brand, M. (1998). A series of no
isthmus (noi) alleles of the zebrafish pax2.1 gene reveals multiple signaling
events in development of the midbrain-hindbrain boundary.
Development 125,3049
-3062.
Maciag, T. and Friesel, R. E. (1995). Molecular mechanisms of fibroblast growth factor-1 traffick, signaling and release. Thromb. Haemost. 74,411 -414.[Medline]
Maroon, H., Walshe, J., Mahmood, R., Kiefer, P., Dickson, C. and
Mason, I. (2002). Fgf3 and Fgf8 are required together for
formation of the otic placode and vesicle. Development
129,2099
-2108.
Mason, C., Lake, M., Nebreda, A. and Old, R. (1996). A novel MAP kinase phosphatase is localised in the branchial arch region and tail tip of Xenopus embryos and is inducible by retinoic acid. Mech. Dev. 55,133 -144.[CrossRef][Medline]
Maves, L., Jackman, W. and Kimmel, C. B. (2002). FGF3 and FGF8 mediate a rhombomere 4 signaling activity in the zebrafish hindbrain. Development 129,3825 -3837.[Medline]
Melby, A. E., Beach, C., Mullins, M. and Kimelman, D. (2000). Patterning the early zebrafish by the opposing actions of bozozok and vox/vent. Dev. Biol. 224,275 -285.[CrossRef][Medline]
Mercola, M., Melton, D. A. and Stiles, C. D. (1988). Platelet-derived growth factor A chain is maternally encoded in Xenopus embryos. Science 241,1223 -1225.[Medline]
Mitchell, T. S. and Sheets, M. D. (2001). The FGFR pathway is required for the trunk-inducing functions of Spemann's organizer. Dev. Biol. 237,295 -305.[CrossRef][Medline]
Molenaar, M., van de Wetering, M., Oosterwegel, M., Peterson-Maduro, J., Godsave, S., Korinek, V., Roose, J., Destree, O. and Clevers, H. (1996). XTcf-3 transcription factor mediates beta-catenin-induced axis formation in Xenopus embryos. Cell 86,391 -399.[Medline]
Montero, J. A., Kilian, B., Chan, J., Bayliss, P. E. and Heisenberg, C. P. (2003). Phosphoinositide 3-kinase is required for process outgrowth and cell polarization of gastrulating mesendodermal cells. Curr. Biol. 13,1279 -1289.[CrossRef][Medline]
Moreno, T. A. and Kintner, C. (2004). Regulation of segmental patterning by retinoic acid signaling during Xenopus somitogenesis. Dev. Cell 6, 205-218.[CrossRef][Medline]
Nasevicius, A. and Ekker, S. C. (2000). Effective targeted gene `knockdown' in zebrafish. Nat. Genet. 26,216 -220.[CrossRef][Medline]
Niehrs, C. and Meinhardt, H. (2002). Modular feedback. Nature 417,35 -36.[CrossRef][Medline]
Pera, E. M., Wessely, O., Li, S. Y. and de Robertis, E. M. (2001). Neural and head induction by insulin-like growth factor signals. Dev. Cell 1,655 -665.[Medline]
Pera, E. M., Ikeda, A., Eivers, E. and de Robertis, E. M.
(2003). Integration of IGF, FGF, and anti-BMP signals via Smad1
phosphorylation in neural induction. Genes Dev.
17,3023
-3028.
Powers, C. J., McLeskey, S. W. and Wellstein, A.
(2000). Fibroblast growth factors, their receptors and signaling.
Endocr. Relat. Cancer 7,165
-197.
Raible, F. and Brand, M. (2001). Tight transcriptional control of the ETS domain factors Erm and Pea3 by Fgf signaling during early zebrafish development. Mech. Dev. 107,105 -117.[CrossRef][Medline]
Reifers, F., Bohli, H., Walsh, E. C., Crossley, P. H., Stainier,
D. Y. and Brand, M. (1998). Fgf8 is mutated in zebrafish
acerebellar (ace) mutants and is required for maintenance of
midbrain-hindbrain boundary development and somitogenesis.
Development 125,2381
-2395.
Rintelen, F., Hafen, E. and Nairz, K. (2003).
The Drosophila dual-specificity ERK phosphatase DMKP3 cooperates with the ERK
tyrosine phosphatase PTP-ER. Development
130,3479
-3490.
Sater, A. K., El-Hodiri, H. M., Goswami, M., Alexander, T. B., Al-Sheikh, O., Etkin, L. D. and Akif Uzman, J. (2003). Evidence for antagonism of BMP-4 signals by MAP kinase during Xenopus axis determination and neural specification. Differentiation 71,434 -444.[CrossRef][Medline]
Schohl, A. and Fagotto, F. (2002).
Beta-catenin, MAPK and Smad signaling during early Xenopus development.
Development 129,37
-52.
Schohl, A. and Fagotto, F. (2003). A role for
maternal beta-catenin in early mesoderm induction in Xenopus. EMBO
J. 22,3303
-3313.
Slack, J. M., Darlington, B. G., Heath, J. K. and Godsave, S. F. (1987). Mesoderm induction in early Xenopus embryos by heparin-binding growth factors. Nature 326,197 -200.[CrossRef][Medline]
Stewart, A. E., Dowd, S., Keyse, S. M. and McDonald, N. Q. (1999). Crystal structure of the MAPK phosphatase Pyst1 catalytic domain and implications for regulated activation. Nat. Struct. Biol. 6,174 -181.[CrossRef][Medline]
Sun, X., Mariani, F. V. and Martin, G. R. (2002). Functions of FGF signalling from the apical ectodermal ridge in limb development. Nature 418,501 -508.[CrossRef][Medline]
Trumpp, A., Depew, M. J., Rubenstein, J. L., Bishop, J. M. and
Martin, G. R. (1999). Cre-mediated gene inactivation
demonstrates that FGF8 is required for cell survival and patterning of the
first branchial arch. Genes Dev.
13,3136
-3148.
Tsang, M., Friesel, R., Kudoh, T. and Dawid, I. B. (2002). Identification of Sef, a novel modulator of FGF signalling. Nat. Cell Biol. 4, 165-169.[CrossRef][Medline]
Tsang, M., Kim, R., de Caestecker, M. P., Kudoh, T., Roberts, A. B. and Dawid, I. B. (2000). Zebrafish nma is involved in TGFbeta family signaling. Genesis 28, 47-57.[CrossRef][Medline]
Turner, D. L. and Weintraub, H. (1994). Expression of achaete-scute homolog 3 in Xenopus embryos converts ectodermal cells to a neural fate. Genes Dev. 8,1434 -1447.[Abstract]
Wakioka, T., Sasaki, A., Kato, R., Shouda, T., Matsumoto, A., Miyoshi, K., Tsuneoka, M., Komiya, S., Baron, R. and Yoshimura, A. (2001). Spred is a Sprouty-related suppressor of Ras signalling. Nature 412,647 -651.[CrossRef][Medline]
Walshe, J., Maroon, H., McGonnell, I. M., Dickson, C. and Mason, I. (2002). Establishment of hindbrain segmental identity requires signaling by FGF3 and FGF8. Curr. Biol. 12,1117 -1123.[CrossRef][Medline]
Walshe, J. and Mason, I. (2003). Unique and
combinatorial functions of Fgf3 and Fgf8 during zebrafish forebrain
development. Development
130,4337
-4349.
Westerfied, M. (1993). The Zebrafish Book. Oregon: University Oregon Press.
Whitman, M. and Melton, D. A. (1992). Involvement of p21ras in Xenopus mesoderm induction. Nature 357,252 -254.[CrossRef][Medline]
Wishart, M. J., Denu, J. M., Williams, J. A. and Dixon, J.
E. (1995). A single mutation converts a novel phosphotyrosine
binding domain into a dual-specificity phosphatase. J. Biol.
Chem. 270,26782
-26785.
Wylie, C., Kofron, M., Payne, C., Anderson, R., Hosobuchi, M.,
Joseph, E. and Heasman, J. (1996). Maternal beta-catenin
establishes a `dorsal signal' in early Xenopus embryos.
Development 122,2987
-2996.
Zhang, J., Zhou, B., Zheng, C. F. and Zhang, Z. Y.
(2003). A bipartite mechanism for ERK2 recognition by its cognate
regulators and substrates. J. Biol. Chem.
278,29901
-29912.
Zhao, Y. and Zhang, Z. Y. (2001). The mechanism
of dephosphorylation of extracellular signal-regulated kinase 2 by
mitogen-activated protein kinase phosphatase 3. J. Biol.
Chem. 276,32382
-32391.
Related articles in Development: