1 Developmental Biology Center, University of California, Irvine, CA 92697,
USA
2 National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
3 Suntory Institute for Bioorganic Research, Osaka 618, Japan
¶ Author for correspondence (e-mail: hrbode{at}uci.edu)
Accepted 15 February 2005
![]() |
SUMMARY |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: Hydra, Hym-301, Peptide, Tentacle formation
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The animal consists of a single oral-aboral axis with radial symmetry.
Along the axis are three regions: the head, body column and foot, or basal
disk. Because of the tissue dynamics of an adult hydra, the processes
governing axial patterning, morphogenesis, cell differentiation and cell
division are constantly active (e.g. Bode,
2003). Hence, the signalling pathways involved in these processes
are also continuously active. In the context of the adult animal it has been
shown that the Wnt pathway is involved in the head organizer
(Hobmayer et al., 2000
) (M.
Broun, L.G., B. Reinhardt and H.R.B., unpublished), while the BMP5-8
(Reinhardt et al., 2004
),
Hedgehog (K. Kaloulis, PhD Thesis, University of Geneva, 2000) and an
RTK (Bridge et al., 2000
)
pathways affect axial patterning processes. Hence, not only are these
bilaterian pathways present in cnidarians, they appear to have similar
functions.
Another set of signalling pathways involves peptides. For example, peptides
affect developmental processes in bilaterians, such as cell proliferation
and/or differentiation [e.g. vasopressin
(Naro et al., 1997),
vasoactive intestinal peptide (Gressens et
al., 1997
), substance P (Kishi
et al., 1996
) and gastrin-releasing peptide
(Jensen et al., 2001
)] or
morphogenesis [e.g. bombesin (Sunday et
al., 1993
), parathyrod hormone-related peptide
(Weir et al., 1996
)]. None of
these peptides has been isolated from hydra so far. However, several novel
peptides have been isolated from hydra and other cnidarians. More recently, a
systematic effort has yielded a large number of novel peptides
(Takahashi et al., 1997
),
which are currently being characterized.
Of the peptides characterized so far, five affect patterning processes. Two
of them, the Head Activator (Schaller,
1973; Bodenmuller and Schaller, 1981) and Heady
(Lohmann and Bosch, 2000
), are
involved in head formation as well as in the initiation of bud formation
(Hobmayer et al., 1997
). The
other three: pedin (Hoffmeister,
1996
) pedibin/Hym-346
(Hoffmeister, 1996
;
Grens et al., 1999
) and
Hym-323 (Harafuji et al.,
2001
) promote foot formation. So far the peptides shown to affect
patterning processes affect the formation of either the head or foot as a
whole. Here, we present evidence that a novel peptide, Hym-301, which was
isolated as part of the systematic effort described above
(Takahashi et al., 1997
) plays
a role in a specific part of the head, namely in determining the number of
tentacles formed.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Isolation and characterization of the gene encoding Hym-301
A full-length cDNA encoding Hym-301 was obtained in three steps.
(1) A short cDNA encoding most of Hym-301 was obtained by PCR. Total RNA isolated from budding polyps was used as a template for the synthesis of first strand cDNA using a specific kit (Pharmacia) for this purpose. PCR was carried out using the first strand cDNA, degenerate primers and Taq DNA polymerase (Boehringer Mannheim) for 30 cycles of 94°C for 15 seconds, 50°C for 30 seconds and 68°C for 30 seconds. The fully degenerate primers used corresponded to the amino acids 3-8 (PRRCYL) of Hym-301, and a complementary primer corresponding to the amino acids 9-14 (NGYCSP). The PCR products were separated on a 1.5% agarose gel; the region slightly above the primers was isolated and the DNA isolated with a Mermaid kit (BIO 101). Subsequently, the DNA was ligated into the pCR2.1 plasmid (Invitrogen). After sequencing, a sequence encoding PRRCYLNGYCSP of the Hym-301 peptide was obtained.
(2) 3'RACE was carried out to extend the cDNA in the 3' region making use of the nucleotide sequence determined for Hym-301. The first strand cDNA was synthesized using total RNA as a template, an oligo-dT primer anchored with an M13 sequence (5'-CAGCACTGACCCTTTTGT15-3') and AMV reverse transcriptase (Boehringer Mannheim). PCR was carried out using the cDNA, a primer corresponding to the amino acids 5-10 of Hym-301 (5'-AGATGCTACTTGAATGG-3'), a downstream primer of M13 sequence and Taq DNA polymerase for 30 cycles as described above. The amplified DNA was separated on a 1% agarose gel and a 200 bp fragment was detected. The fragment was purified using a GENECLEAN II (BIO 101) kit and cloned into the pCR 2.1 plasmid.
(3) This partial Hym-301 cDNA sequence was used to screen a Hydra cDNA
library constructed in Uni-ZapII (Stratagene)
(Yum et al., 1998). Screening
the library yielded a single clone containing the complete open reading frame
was obtained (DDBJ Accession Number: AB106883).
In situ hybridization
Digoxigenin-labelled antisense and sense probes derived from the
full-length Hym-301 cDNA precursor sequence were synthesized using an RNA in
vitro transcription kit (Boehringer Mannheim). Whole-mount in situ
hybridization was carried out as described previously
(Grens et al., 1996). Samples
were hybridized for 48 hours using a probe concentration of 0.1 ng/µl, and
then stained with BM-purple (Boehringer Mannheim) at 37°C for 1 hour in
the dark. Thereafter, they were rinsed and incubated in 100% ethanol and
subsequently mounted in Euparal (Asco Laboratories).
RNAi
Hym-301 dsRNA and luciferase dsRNA were synthesized as
described by Fire et al. (Fire et al.,
1998). Both dsRNAs were introduced into stage 2-3 developing buds
with localized electroporation (LEP) as described previously
(Smith et al., 2000
). They
were also introduced into regenerating heads as follows. Animals were bisected
directly beneath the head, allowed to regenerate for 24 hours and then mounted
on glass rods. To do this, the foot and the body column were first bisected
parallel to the body axis. Then, a glass needle inserted and threaded up
through the gastric cavity to the regenerating head. The other end of the
needle was inserted into an agar layer in a petri dish. Then, the LEP
procedure was carried out introducing the Hym-301 dsRNA or
luciferase dsRNA into the regenerating head from the apical end. The
electroporation conditions and dsRNA concentrations were the same as used for
introducing the dsRNA into developing buds.
The effect of Hym-301 dsRNA on the level of Hym-301 mRNA
in buds was analyzed by RT-PCR as described previously
(Technau and Bode, 1999).
Tissue was collected from developing buds for each sample that had been
treated with LEP. Total RNA was isolated from each sample, and RT-PCR was
carried out using primers for the Hym-301 gene (forward,
5'-TTTGCACTTATTGATGCGCGA-3'; reverse,
5'-ACCAGGAGAACAATAACCATT-3'). The hydra EF1
gene
was used as an internal control (Technau
and Bode, 1999
). PCR conditions were as follows; 1 cycle at
94°C for 3 minutes followed by 35 cycles of the following steps: 30
seconds at 94°C, 30 seconds at 50°C and 1 minute at 72°C.
Tissue manipulations
Head and foot regeneration
Head and foot regeneration experiments were carried out using non-budding
polyps of the 105 strain of H. magnipapillata. The polyps were
bisected in the middle of the body column, and the upper and lower halves
allowed to regenerate a foot and head respectively in the presence or absence
of 106 M Hym-301. The culture solution with or without the
peptide was replaced daily. To assay head regeneration, two methods were used:
(1) the number of tentacles formed was counted daily; and (2) whether a mouth
had formed was examined daily by treating regenerates with glutathione (GSH at
105 M) for 20 minutes
(Lenhoff, 1961). Treated
polyps were washed with the culture solution and allowed to continue
regeneration. Foot regeneration was assayed by determining if an animal was
attached to the floor of the culture dish in which the animals were undergoing
regeneration.
LiCl treatment
Non-budding adults of the Basel strain of H. vulgaris were exposed
to 2 mM LiCl in hydra medium for 2 days, and then returned to hydra
medium.
Measurement of the labelling index
Periodically after bisection, regenerating animals were injected with 5 mM
BrdU, and the labelling index of the epithelial cells was measured as
described by Plickert and Kroiher
(Plickert and Kroiher, 1988)
and Teragawa and Bode (Teragawa and Bode,
1990
).
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
|
|
When a hydra is bisected in the body column, a head regenerates at the apical end of the lower half in 3-4 days, while a foot regenerates at the basal end of the upper half in 1-2 days. The pattern of expression at the apical end of the lower half is similar to that observed during bud formation. 6 hours after bisection, there is very little expression (Fig. 4A). By 12 hours (Fig. 4B) and with increasing intensity over 2 days (Fig. 4C,D), the gene is expressed in the upper half of the regenerate. Then as the tentacles begin to appear by 72 hours (Fig. 4E) and elongate by 96 hours (Fig. 4F), expression vanishes in the emerging tentacles, and becomes increasingly restricted to the upper end of the body column. Expression is also absent from the apical tip of the developing hypostome (Fig. 4E,F). Hym-301 was not expressed during foot regeneration (data not shown), which is consistent with the absence of its expression in the adult (Fig. 2A).
Hym-301 affects the number of tentacles formed
The expression patterns indicates the gene could play a role in tentacle
formation and in hypostome formation. To determine if the gene affected
tentacle formation, animals were bisected in the middle of the body column and
the basal halves allowed to regenerate heads in the presence or absence of the
Hym-301 peptide. As the tentacles form in a regenerating head in 4-6 days,
regenerates were examined daily for 7 days. Exposure to 108
M or 107 M peptide had no effect. However, treatment with
either 106 M or 105 M resulted in an
increase in the number of tentacles that formed
(Fig. 5A). As the number of
tentacles formed is correlated with the diameter of the tentacle zone
(Bode and Bode, 1984), Hym-301
might affect the rate of epithelial cell division in the developing head. This
possibility was assayed by bisecting animals in the middle of the body column,
exposing them to 106 M Hym-301 for 3 days. Daily, the apical
quarter as well as the next quarter was isolated from control and from
peptide-treated regenerating animals, and the labelling index of the
epithelial cells measured. As shown in
Table 1, the peptide had no
significant effect on the labelling index in either region, and hence, the
rate of cell division. Thus, the increase in tentacle number is not due to an
increase in the number of epithelial cells in the regenerating head. The
peptide also had no effect on the rate of tentacle formation nor on the final
length of the tentacles (data not shown).
|
|
|
|
|
As the major effect of treatment with the Hym-301 peptide treatment or RNAi was the alteration in the number of tentacles formed, the gene appears to be required for the regulation of the number of tentacles formed.
Hym-301 directly acts on epithelial cells
Hym-301 is produced in ectodermal epithelial cells. What is/are the target
cell(s)? Hydra has three cell lineages: the ectodermal epithelial cell,
endodermal epithelial cell and interstitial cell lineage. The latter consists
of a multipotent stem cell and several classes of differentiation products
(Bode, 1996). Hym-301 could act
directly on epithelial cells of both the ectoderm and endoderm to form
tentacles, or it could act indirectly through a cell type of the interstitial
cell lineage, such as the neurons. To determine if cells of the interstitial
cell lineage are involved, epithelial animals, which are devoid of cells of
the interstitial cell lineage (Sugiyama
and Fujisawa, 1978
), were bisected in the middle of the body
column and allowed to regenerate in the presence or absence of
106 M Hym-301. As epithelial animals have somewhat larger
heads, which regenerate more slowly, the analysis was carried out after 10
days instead of 7 days for the normal animals. The larger number of tentacles
in the epithelial animals is also a reflection of the larger head size of
these animals compared with normal animals of this species of hydra. As shown
in Table 3, Hym-301
significantly increased the number of tentacles formed in the epithelial
hydra, indicating that the peptide acts directly on the epithelial cells.
Hence, the cells of the interstitial cell lineage are not required for the
activity of Hym-301.
|
When hydra are treated with 2 mM LiCl, the level of the head activation
gradient is raised throughout the body column. This was demonstrated by
transplanting pieces isolated from different levels of the body column tissue
of a donor treated with 2 mM LiCl for 2 days to untreated hosts at the same
axial level. A higher fraction of the Li+-treated transplants for
each axial level formed second axes than did the corresponding control region,
indicating a rise in the head activation level in the Li+-treated
tissue (L.G. and H.R.B., unpublished). Furthermore, this treatment invariably
leads to the formation of ectopic tentacles form along the body column
(Hassel and Bieler, 1996).
Hydra were exposed to 2 mM LiCl and the expression pattern of Hym-301
analyzed at various times after begin of treatment. As shown in
Fig. 8, the pattern of
expression extends further down the body column with increasing time of
exposure to LiCl. As the gradient rises throughout the body column during the
exposure to 2 mM LiCl, the threshold level for Hym-301 expression
would move down the column, which is consistent with the observed changes in
expression of the gene. In turn, this results indicates that Hym-301
expression is regulated by the head activation gradient.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In an adult hydra, the epithelial cells of both tissue layers in the body
column are constantly in the mitotic cycle
(David and Campbell, 1972;
Campbell and David, 1974
). A
consequence of this activity is that tissue of the upper body column is
continuously displaced into the head and sloughed at the extremities. In the
rest of the body column, tissue is displaced down the axis onto developing
buds, which eventually detach, or into the foot and sloughed
(Campbell, 1967
). Thus, the
animal remains constant in size as it is in a steady state of production and
loss of cells.
The first step, the specification of body column tissue for tentacle
formation takes place within the context of the processes governing axial
patterning. The head organizer in the hypostome
(Broun and Bode, 2002) produces
and transmits a signal to the body column that sets up a morphogenetic
gradient, the head activation gradient, which is maximal in the hypostome and
decreases down the body column. Different values of the gradient define the
different regions: hypostome, tentacle zone, body column and foot. Because of
the tissue dynamics, these processes are constantly active.
As tissue is displaced up the body column, it moves up the head activation gradient, and when it crosses a threshold value it becomes specified for tentacle formation. The evidence for this is the following. Tissue of most of the body column is capable of forming either a head or a foot. However, tissue in the upper one-eighth of the body column depending on the species of hydra is no longer capable of foot formation (L.G. and H.R.B., unpublished). As shown by Hobmayer et al. (Hobmayer et al., 1991), this tissue as well as that in the tentacle zone has become specified/committed to tentacle formation. In the head, this commitment is confined to the lower part of the head, the tentacle zone, as tissue more apically in the hypostome does not form tentacles.
The second step involves commitment of tissue in the tentacle zone to the
formation of individual tentacles. During bud formation or head regeneration,
this occurs in evenly spaced spots located around the developing tentacle
zone, as illustrated with two molecular markers. When a developing bud has
elongated into a cylindrical shell, both HyAlx and
HyBMP5-8b, hydra orthologues of aristaless and
BMP5-8, are expressed in a ring of spots below the apical tip of the
bud (Smith et al., 2000;
Reinhardt et al., 2004
). The
same sequence of steps occurs during head regeneration. The spots are evenly
spaced, suggesting the involvement of a mechanism that sets up a spacing
pattern. This view is supported by the following observation. Increasing the
diameter of a regenerating head by threading a thin glass needle through the
gastric cavity following bisection results in the formation of more tentacles
than in simply bisected animals (Bode and
Bode, 1984
).
After the formation of the pattern of spots, each spot evaginates and
elongates into a tentacle as tissue from the tentacle zone is displaced onto
each tentacle. This is the third step. As a tentacle evaginates and elongates,
HyAlx and HyBMP5-8b continue to be expressed as rings at the
tentacle zone/tentacle border (Smith et
al., 2000; Reinhardt et al.,
2004
). They mark a sharp transition in the activity of cells
moving across the tentacle zone/tentacle border.
As cells are displaced through the tentacle zone, they remain in the
mitotic cycle until they cross the tentacle/tentacle zone border onto
tentacles. Then, they abruptly cease dividing and differentiate
(Holstein et al., 1991). The
expression patterns of a number of genes also illustrates this sudden change.
Cnotx (Smith et al.,
1999
) and Cnox-3
(Bode, 2001
), the hydra
orthologues of Otx and labial/Hox-1 are expressed
in epithelial cells of the tentacle zone, but cease expression at the tentacle
zone/tentacle border. Conversely, TS-19, a cell surface antigen
(Bode et al., 1988
), an annexin
gene (Schlaepfer et al.,
1992
), HMP1 a metalloprotease
(Yan et al., 1995
) and HTK
(Steele et al., 1996
) are
expressed immediately as the epithelial cells cross the tentacle/tentacle zone
border and subsequently all along the tentacles.
Most likely, the two genes expressed at the border, HyAlx and
HyBMP5-8b play a role in the differentiation of cells as they cross
the border, or in the change in cell shape to convert tentacle zone tissue
into tentacle tissue. Transiently reducing the level of HyAlx mRNA in
a developing bud with RNAi leads to a delay in tentacle formation, which
supports this view (Smith et al.,
2000).
Hym-301 affects the number of tentacles formed
Several results indicate that Hym-301 may play a role in the first step,
and clearly plays a role in the second step of tentacle formation.
A role in specification of tissue for tentacle formation
As tissue is displaced up the body column, the level of head activation in
the tissue rises passing a threshold for commitment of tissue for tentacle
formation. Two results indicate that Hym-301 expression occurs above
this threshold level.
(1) In the normal animal the gene is expressed in the upper one-eighth of
the body column, the tentacle zone and the hypostome. Tissue in this part of
the body column and the tentacle zone is specified/committed to tentacle
formation (Hobmayer et al.,
1990).
(2) In LiCl-treated animals, the head activation gradient is raised throughout the body column (L.G. and H.R.B., unpublished). This rise is correlated with Hym-301 expression being displaced down the body column. And, the longer the treatment with LiCl, the further down the body column the gene was expressed. This rise in head activation was also reflected in the formation of ectopic tentacles along the body column. Thus, there is a strong correlation between Hym-301 expression and tentacle formation.
However, it is unlikely that the Hym-301 peptide commits tissue to tentacle formation. The gene is also expressed in the hypostome, where tentacles do not form. In addition, during early stages of bud formation and head regeneration, Hym-301 is expressed throughout much of a developing bud and the upper half of the body column of a hydra regenerating a head where tentacles will not form. Instead, these results are consistent with the expression of the gene above a threshold level of the head activation gradient. A plausible explanation for these results is that the Hym-301 peptide is involved in specifying, but not committing epithelial tissue to tentacle formation. In tissue that will develop into a hypostome, or that is in the hypostome, additional factors required for commitment to tentacle formation are not present. Or, other molecular mechanisms may override tentacle specification.
Role in the number of tentacles formed
Hym-301 has a clear role in the second step: the determination of the
number of tentacles formed in a developing head. Addition of the peptide to a
regenerating head results in an increase in the number of tentacles formed.
Reduction of the level of the peptide with RNAi during bud formation or head
regeneration leads to a reduction in the number of tentacles formed. As in
normal development, the tentacles formed are evenly spaced after these
treatments. This indicates that a mechanism generating a spacing pattern is
involved in the process of tentacle formation, and that the Hym-301 peptide
may play a role in this mechanism.
Assuming a spacing pattern is involved, an increase in the number of tentacles could be the result of an increase in the diameter of the tentacle zone where the tentacles will form. If so, one would expect an increase in the number of epithelial cells in the developing tentacle zone. As treatment of epithelial animals (animals consisting only of epithelial cells) with the Hym-301 peptide also results an increase in the number of tentacles formed, the peptide clearly can act directly on epithelial cells. However, treatment with the peptide did not lead to an increase in the rate of cell division, or in the number of epithelial cells in a regenerating head. Thus, the peptide must affect the spacing pattern in some other manner.
The two roles of Hym-301 could be part of a single mechanism
Gierer and Meinhardt (Gierer and
Meinhardt, 1972) constructed a model based on a reaction-diffusion
mechanism to explain axial patterning in hydra. The essence of the model is
that an autocatalytic activator rises to a threshold level committing the
tissue to a particular development: for example, head formation. At the same
time, the activator induces the production of an inhibitor which diffuses to
prevent formation of another activator peak in the vicinity.
Meinhardt (Meinhardt, 1993)
refined the model by considering the formation of the tentacles and the
hypostome/head organizer to be based on separate reaction-diffusion
mechanisms. The mechanism for tentacle formation is activated above a
threshold value of head activation, which would be in the tentacle zone. At a
higher level of positional value in the prospective hypostome, the
activator/inhibitor mechanism for hypostome/head organizer would be activated,
which in turn blocks tentacle activation. This confines tentacle activation to
a ring of tissue, the tentacle zone beneath the hypostome.
The mechanism for tentacle formation involves the autocatalytic rise of tentacle activation (TA) coupled with the activator-induced production of a tentacle inhibitor (TI). As the rise in tentacle activation around the tentacle zone is unlikely to be uniform, those spots of TA which started earlier will produce more TI, and block the rise of tentacle activation in their neighbourhood. Such a mechanism will result in a fairly evenly spaced pattern of TA peaks each of which will eventually form a tentacle.
As Hym-301 is expressed throughout the tentacle zone, it may play a role in the tentacle activation process. Then, external addition of peptide would raise the overall concentration of the peptide in the tentacle zone causing the more rapid rise of the TA throughout the tentacle zone. In turn, this would result in more TA peaks reaching the level where commitment to tentacle formation occurs before sufficient amounts of tentacle inhibitor are produced by developing neighbouring peaks. This would result in a spacing pattern with more tentacles. Conversely, if the amount of Hym-301 peptide is lower than normal, the rise in TA would be slower, and fewer peaks would reach the level where they are resistant to the continuously produced tentacle inhibition. This would result in a spacing pattern with fewer tentacles.
Such a mechanism could account for both of the activities proposed for the Hym-301 peptide proposed in the previous section. First, the peptide would have a role in specifying tissue for tentacle formation in that it is part of the tentacle activation process. And second, it would have a role in the number of tentacles formed as it affects the rate of rise in a TA peak. The final number of tentacles formed is a function of this rate or TA rise.
Role of peptides in axial patterning in hydra
A number of peptides have been isolated from hydra and shown to participate
in axial patterning processes. As mentioned earlier, three of them, pedin
(Hoffmeister, 1996),
pedibin/Hym-346 (Hoffmeister,
1996
) and Hym-323 (Harafugi et al., 2001), affect the rate of foot
regeneration, while the head activator increases the rate of head as well as
foot regeneration (Schaller,
1973
; Javois and Tombe,
1991
; Javois and
Frazier-Edwards, 1991
). More direct roles have been identified for
these two peptides, as well as for a third. Both pedibin/Hym-346
(Grens et al., 1996
) and
Hym-323 (Harafugi et al., 2001) lower the head activation gradient, while
Heady appears to be involved in the development of the head organizer (Lohman
and Bosch, 2000). In this regard, Hym-301 is similar to the latter group as it
affects a specific patterning event.
Whether all five of the peptides directly affect the epithelial cells of
the two layers, the ectoderm and endoderm, which carry out the patterning
processes is not clear. The head activator, pedin and pedibin/Hym-346 also
affect the rates of cell division and neuron differentiation
(Schaller et al., 1989;
Hoffmeister, 1996
). Thus, it
is plausible that these peptides affect patterning processes indirectly. By
contrast, Hym-323 (Harafugi et al., 2001) and Hym-301 have been shown to have
similar effects on epithelial animals as they do on normal hydra. As the
epithelial animals consist only of the epithelial cells of the two tissue
layers, these peptides affect the epithelial cells directly.
Of the common signalling pathways that affect developmental processes in
bilaterians, three of them are known to affect patterning processes in hydra.
The Wnt pathway is involved in the formation of the head organizer
(Hobmayer et al., 2000) (M.
Broun, L.G., B. Reinhardt and H.R.B., unpublished), while the members of the
RTK and BMP pathways are involved in the patterning of the lower part of the
body column (Steele et al.,
1996
; Reinhardt et al.,
2004
), which involves the head activation gradient. Heady may also
affect the organizer (Lohmann and Bosch,
2000
), while both pedibin/Hym-346 and Hym-323
(Grens et al., 1996
;
Harafuji et al., 2001
) can
lower the head activation gradient. Hence, it appears as though the
well-established signalling pathways as well as pathways initiated by some of
these peptides may be involved, and possibly interacting, in these patterning
processes.
This raises the issue of whether this is peculiar to hydra, or whether it
also occurs in bilaterians. That one of these peptides also plays a role in
bilaterians has been shown for the head activator. This peptide has also been
isolated from the hypothalamus and intestine of rats and humans where it
appears to have a role in neuron differentiation
(Schaller, 1975; Bodenmuller
et al., 1980; Bodenmuller and Schaller, 1981). Thus, it is plausible that such
peptides represent a class of signalling molecules that have been initially
uncovered in hydra, and may also exist in bilaterians.
![]() |
ACKNOWLEDGMENTS |
---|
![]() |
Footnotes |
---|
Present address: Department of Biology, Faculty of Science, Ochanomizu,
University, Tokyo 112-8610, Japan
Present address: Department of Biological Sciences, Sungkyunkwan
University, Suwon 440-746, Korea
Present address: Laboratory of Bioorganic Chemistry, National Institute of
Health, Bethasda, MD 20892, USA
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Bode, H. R. (1996). The interstitial cell
lineage of hydra: a stem cell system that arose early in evolution.
J. Cell. Sci. 109,1155
-1164.
Bode, H. R. (2001). Role of Hox genes in axial patterning in Hydra. Am. Zool. 41,621 -628.
Bode, H. R. (2003). Head regeneration in Hydra. Dev. Dyn. 226,225 -236.[CrossRef][Medline]
Bode, P. M. and Bode, H. R. (1984). Formation of pattern in regenerating tissue of Hydra attenuata. III. The shaping of the body column. Dev. Biol. 106,315 -325.[CrossRef][Medline]
Bode, P., Amad, T., Koizumi, O., Nakashima, Y., Grimmelikhuijzen, C. and Bode, H. R. (1988). Development of the two-part pattern during regeneration of the head in hydra. Development 102,223 -235.[Abstract]
Bodenmueller, H. and Schaller, H. C. (1981). Conserved amino acid sequence of neuropeptide, the head activator, from coelenterates to humans. Nature 293,579 -580.[CrossRef][Medline]
Bodenmueller, H., Schaller, H. C. and Darai, G. (1980). Human hypothalamus and intestine contain a hydra-neuropeptide. Neurosci. Lett. 16, 71-74.[CrossRef][Medline]
Bridge, D. M., Stover, N. A. and Steele, R. E. (2000). Expression of a novel receptor tyrosine kinase gene and a paired-like homeobox gene provides evidence of differences in patterning at the oral and aboral ends of hydra. Dev. Biol. 220,253 -262.[CrossRef][Medline]
Broun, M. and Bode, H. R. (2002). Characterization of the head organizer in hydra. Development 129,875 -884.[Medline]
Campbell, R. D. (1967). Tissue dynamics of steady-state growth in Hydra litoralis. I. Patterns of cell division. Dev. Biol. 15,487 -502.[CrossRef][Medline]
Campbell, R. D. and David, C. N. (1974). Cell cycle kinetics and development of Hydra attenuata. I. Interstitial cells. J. Cell Sci. 16,349 -358.[Medline]
Darmer, D., Hausen, F., Nothacker, H.-P., Bosch, T. C. G., Williamson, M. and Grimmelikhuijzen, C. J. P. (1998). Three different prohormones yield a variety of Hydra-RFamide (Arg-Phe-NH2) neuropeptides in Hydra magnipapillata. Biochem. J. 332,403 -412.[Medline]
David, C. N. and Campbell, R. D. (1972). Cell cycle kinetics and development of Hydra attenuata. I. Epithelial cells. J. Cell Sci. 11,557 -568.[Medline]
Escriva, H., Safi, R., Hanni, C., Langlois, M. C.,
Saumitou-Laprade, P., Stehelin, D., Capron, A., Pierce, R. and Laudet, V.
(1997). Ligand binding was acquired during evolution of nuclear
receptors. Proc. Natl. Acad. Sci. USA
94,6803
-6808.
Fire, A., Xu, S., Montgomery, M. K., Kostas, S. A., Driver, S. E. and Mello, C. C. (1998). Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans.Nature 391,806 -810.[CrossRef][Medline]
Gierer, A. and Meinhardt, H. (1972). A theory of biological pattern formation. Kybernetik 12, 30-39.[CrossRef][Medline]
Grens, A., Gee, L., Fisher, D. A. and Bode, H. R. (1996). CnNK-2, an NK-2 Homeobox gene, has a role in patterning the basal end of the axis in Hydra. Dev. Biol. 180,473 -488.[CrossRef][Medline]
Grens, A., Shimizu, H., Hoffmeister, S., Bode, H. R. and
Fujisawa, T. (1999). Pedibin/Hym-346 lowers positional value
thereby enhancing foot formation in hydra. Development
126,517
-524.
Gressens, P., Paindavine, B., Hill, J., Brenneman, D. F. and Evrard, P. (1997). Growth factor peptides of VIP during early brain development. Whole embryo culture and in vivo studies. Ann. New York Acad. Sci. 814,152 -160.[Abstract]
Harafuji, N., Takahashi, T., Hatta, M., Tezuka, H., Morishita,
F., Matsushima, O. and Fujisawa, T. (2001). Enhancement of
foot formation in Hydra by a novel epitheliopeptide, Hym-323.
Development 128,437
-446.
Hassel, M. and Bieller, A. (1996). Stepwise transfer from high to low lithium concentrations increases the head-forming potential in Hydra vulgaris and possibly activates the PI cycle. Dev. Biol. 177,439 -448.[CrossRef][Medline]
Hassel, M., Albert, K. and Hofheinz, S. (1993). Pattern formation in Hydra vulgaris is controlled by lithium-sensitive processes. Dev. Biol. 156,362 -371.[CrossRef][Medline]
Hayward, D. C., Samuel, G., Pontynen, P. C., Catmull, J., Saint,
R., Miller, D. J. and Ball, E. E. (2002). Localized
expression of a dpp/BMP2/4 ortholog in a coral embryo. Proc. Natl.
Acad. Sci. USA 99,8106
-8111.
Hobmayer, B. (1996). Identification of a hydra homologue of the ß-catenin/plakoglobin/armadillo gene family. Gene 172,155 -159.[CrossRef][Medline]
Hobmayer, B., Holstein, T. W. and David, C. N. (1997). Stimulation of tentacle and bud formation by the neuropeptide head activator in Hydra magnipapillata. Dev. Biol. 183,1 -8.[CrossRef][Medline]
Hobmayer, B., Rentzsch, F., Kuhn, K., Happel, C. M., von Laue, C. C., Snyder, P., Rothbacher, U. and Holstein, T. W. (2000). WNT signalling molecules act in axis formation in the diploblastic metazoan Hydra. Nature 407,186 -189.[CrossRef][Medline]
Hobmayer, B., Holstein, T. W. and David, C. N. (1990). Tentacle morphogenesis in hydra. I. The role of the head activator. Development 109,887 -895.[Abstract]
Hoffmeister, S. A. H. (1996). Isolation and
characterization of two new morphogenetically active peptides from Hydra
vulgaris. Development 122,1941
-1948.
Holstein, T. W., Hobmayer, E. and David, C. N. (1991). Pattern of epithelial cell cycling in hydra. Dev. Biol. 148,602 -611.[CrossRef][Medline]
Javois, L. C. and Frazier-Edwards, A. M. (1991). Simultaneous effects of head activator on the dynamics of apical and basal regeneration in Hydra vulgaris (formerly Hydra attenuata). Dev. Biol. 144, 78-85.[CrossRef][Medline]
Javois, L. C. and Tombe, V. K. (1991). Head activator does not alter head morphology in regenerates of Hydra oligactis. Roux's Arch. Dev. Biol. 199,402 -408.
Jensen, J. A., Carroll, R. E. and Benya, R. V. (2001). The case for gastrin releasing peptide acting as a morphogen when it and its receptor are aberrantly expressed in cancer. Peptides 22,689 -699.[CrossRef][Medline]
Kishi, H., Mishima, H. K., Sakamoto, I. and Yamashita, U. (1996). Stimulation of retinal pigment epithelial cell growth by neuropeptides in vitro. Curr. Eye Res. 15,708 -713.[Medline]
Lenhoff, H. M. (1961). Activation of feeding
reflex in Hydra littoralis. I. Role played by reduced glutathione,
and quantitative assay of the feeding reflex. J. Gen.
Physiol. 45,331
-344.
Lohmann, J. U. and Bosch, T. C. G. (2000). The
novel peptide HEADY specifies apical fate in a simple radially symmetric
metazoan. Genes Dev. 14,2771
-2777.
MacWilliams, H. K. (1983). Hydra transplantation phenomena and the mechanism of Hydra head regeneration. II. Properties of head activation. Dev. Biol. 96,239 -257.[CrossRef][Medline]
Martinez, D. E., Dirksen, M. L., Bode, P. M., Jamrich, M., Steele, R. E. and Bode, H. R. (1997). Budhead, a fork head/HNF-3 homologue, is expressed during axis formation and head specification in hydra. Dev. Biol. 192,523 -536.[CrossRef][Medline]
Meinhardt, H. (1993). A model for pattern formation of hypostome, tentacles and foot in Hydra: How to form structures close to each other, how to form them at a distance. Dev. Biol. 157,321 -333.[CrossRef][Medline]
Minobe, S., Fei, K., Yan, L., Sarras, M., Jr and Werle, M. (2000). Identification and characterization of the epithelial polarity receptor "Frizzled" in Hydra vulgaris. Dev. Genes. Evol. 210,258 -262.[CrossRef][Medline]
Naro, F., Donchenko, K., Minotti, S., Zolla, L., Molinaro, M. and Adamo, S. (1997). Role of phospholipase C and D signaling pathways in vasopressin-dependent myogenic differentiation. J. Cell Physiol. 171,34 -42.[CrossRef][Medline]
Nishimiya-Fujisawa, C. and Sugiyama, T. (1993). Genetic analysis of developmental mechanisms in Hydra. XX. Cloning of interstitial stem cells restricted to the sperm differentiation pathway in Hydra magnipapillata. Dev. Biol. 157, 1-9.[CrossRef][Medline]
Pires-daSilva, A. and Sommer, R. J. (2003). The evolution of signalling pathways in animal development. Nat. Rev. Genet. 4,39 -49.[CrossRef][Medline]
Plickert, G. and Kroiher, M. (1988). Proliferation kinetics and cell lineages can be studied in whole mounts and macerates by means of BrdU/anti-BrdU technique. J. Cell Sci. 28,117 -132.
Reinhardt, B., Broun, M., Blitz, I. L. and Bode, H. R. (2004). HyBMP5-8b, a BMP5-8 orthologue, acts during axial patterning and tentacle formation in hydra. Dev. Biol. 267,43 -59.[CrossRef][Medline]
Schaller, H. C. (1973). Isolation and characterization of a low molecular-weight substance activating head and bud formation in hydra. J. Embryol. Exp. Morphol. 29, 27-38.[Medline]
Schaller, H. C. (1975). A neurohormone from hydra is also present in the rat brain. J. Neurochem. 25,187 -188.[Medline]
Schaller, H. C., Hoffmeister, S. A. and Dubel, S. (1989). Role of the neuropeptide head activator for growth and development in hydra and mammals. Development 107,99 -107.[Medline]
Schlaepfer, D. D., Bode, H. R. and Haigler, H. T. (1992). Distinct cellular expression pattern of annexins in Hydra vulgaris. J. Cell Biol. 118,911 -928.[Abstract]
Shenk, M. A., Bode, H. R. and Steele, R. E.
(1993). Expression of Cnox-2, a HOM/HOX homeobox gene in Hydra is
correlated with axial pattern formation. Development
117,657
-667.
Smith, K. M., Gee, L., Blitz, I. L. and Bode, H. R. (1999). CnOtx, a member of The Otx gene family, has a role in cell movement in hydra. Dev. Biol. 212,392 -404.[CrossRef][Medline]
Smith, K. M., Gee, L. and Bode, H. R. (2000).
HyAlx, an aristaless-related gene, is involved in tentacle formation
in hydra. Development
127,4743
-4752.
Sossin, W. S., Fisher, J. M. and Scheller, R. H. (1989). Cellular and molecular biology of neuropeptide processing and packaging. Neuron 2,1407 -1417.[CrossRef][Medline]
Steele, R. E. (2002). Developmental signalling in Hydra: What does it take to build a "simple" animal? Dev. Biol. 248,199 -219.[CrossRef][Medline]
Steele, R., Lieu, P., Mai, N., Shenk, M. A. and Sarras, M. (1996). Response to insulin and the expression pattern of a gene encoding an insulin receptor homologue suggest a role for an insulin-like molecule in regenerating growth and pattern in Hydra. Dev. Genes Evol. 206,247 -259.[CrossRef]
Stover, N. A. and Steele, R. E. (2001).
Trans-spliced leader addition to mRNAs in a cnidarian. Proc. Natl.
Acad. Sci. USA 98,5693
-5698.
Sugiyama, T. and Fujisawa, T. (1977). Genetic analysis of developmental mechanisms in hydra. III. Characterization of a regeneration deficient strain. J. Embryol. Exp. Morphol. 42,65 -77.
Sugiyama, T. and Fujisawa, T. (1978). Genetic analysis of developmental mechanisms in Hydra. Isolation and characterization of an interstitial cell-deficient strain. J. Cell Sci. 29, 35-52.[Abstract]
Sunday, M. E., Hua, J., Reyes, B., Masui, H. and Torday, J. S. (1993). Antibombesin monoclonal antibodies modulate fetal mouse lung growth and maturation in utero and in organ cultures. Anat Rec. 236,25 -32.[CrossRef][Medline]
Takahashi, T., Muneoka, Y., Lohmann, J., deHaro, L. M.,
Solleder, G., Bosch, T. C. G., David, C. N., Bode, H. R., Koizumi, O.,
Shimizu, H. et al. (1997). Systematic isolation of peptide
signal molecules regulating development in hydra: LWamide and PW families.
Proc. Natl. Acad. Sci. USA
94,1241
-1246.
Technau, U. and Bode, H. R. (1999).
HyBra1, a Brachyury homologue, acts during head formation in
Hydra. Development 126,999
-1010.
Teragawa, C. K. and Bode, H. R. (1990). Spatial and Temporal Patterns of Interstitial Cell Migration in Hydra vulgaris.Dev. Biol. 138,63 -81.[CrossRef][Medline]
Weir, E. C., Philbrick, W. M., Amling, M., Neff, L. A., Baron,
R. and Broadus, E. (1996). Targeted overexpression of
parathyroid hormone-related peptide in chondrocytes causes chondrodysplasia
and delayed endochondral bone formation. Proc. Natl. Acad. Sci.
USA 93,10240
-10245.
Wolpert, L. (1971). Positional information and pattern formation. Curr. Top. Dev. Biol. 6, 183-224.[Medline]
Yan, L., Pollock, G., Nagase, H. and Sarras, M.
(1995). A 25.7x103 hydra metalloproteinase
(HMP1), a member of the astacin family, localizes to the extracellular matrix
of Hydra vulgaris in a head-specific manner and has a developmental
function. Development
121,1591
-1602.
Yum, S., Takahashi, T., Hatta, M. and Fujisawa, T. (1998). The structure and expression of a preprohormone of a neuropeptide, Hym-176 in Hydra magnipapillata. FEBS Lett. 439,31 -34.[CrossRef][Medline]
Related articles in Development: