|
|
|
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online 9 January 2008
doi: 10.1242/dev.007989
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Department of Biological Regulation, Weizmann Institute of Science, Rehovot
76100, Israel
2 University of California-San Diego, Skaggs School of Pharmacy, La Jolla, CA
92093, USA.
* Author for correspondence (e-mail: eldad.tzahor{at}weizmann.ac.il)
Accepted 26 November 2007
 |
SUMMARY |
|---|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Key words: Anterior heart field, Splanchnic mesoderm, Myogenesis, Wnt/β-catenin
|
INTRODUCTION |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
;
Waldo et al., 2001). In mouse
embryos, retrospective lineage analysis has demonstrated the presence of two
heart fields - the first and the second heart field - based on their timing of
entry into the heart and their timing of differentiation
(Buckingham et al., 2005). The
first heart field primarily contributes to the left ventricle, whereas the
second heart field contributes most of the cells of the cardiac OFT and right
ventricle (RV), a majority of cells in the atria, and some cells within the
left ventricle (Black, 2007;
Buckingham et al., 2005;
Garry and Olson, 2006;
Srivastava, 2006). In chick,
the precise boundaries and molecular identities of mesodermal `fields' are
less clear, owing to a lack of genetic and lineage-specific markers for these
early progenitors, as well as differences between chick and mouse models
(Abu-Issa and Kirby, 2007).
Heart development takes place in close apposition to the developing head.
The separation between the heart and the head commences gradually, following
heart-looping stages as the heart shifts caudally. The term
`cardio-craniofacial morphogenetic field' reflects the intimate developmental
relationship between the head, face and heart, which is also reflected in
numerous cardiac and craniofacial birth defects
(Hutson and Kirby, 2003).
Cranial paraxial mesoderm (CPM) cells located anterior to the somites, as
well as prechordal mesoderm, provide the precursors for approximately 60
distinct skeletal muscles in the head, which are used to facilitate food
intake, move the eyeball, provide facial expressions and aid speech in humans
(Wachtler and Jacob, 1986).
CPM cells stream into the neighboring branchial arches (BAs, also known as
pharyngeal arches), the templates of the adult craniofacial structures. Within
the BAs, cranial neural crest cells surround the muscle anlagen
(Noden, 1983;
Trainor et al., 1994); these
cells provide multiple signals that regulate cranial muscle patterning and
differentiation (Rinon et al.,
2007; Tzahor et al.,
2003).
It is well accepted that distinct developmental programs control skeletal
muscle formation in the trunk and in the head (reviewed by
Bothe et al., 2007;
Noden and Francis-West, 2006).
Moreover, muscle myopathies are known to be differentially linked to a
specific trunk or cranial region (Emery,
2002). Similarly, within the head musculature, eye muscles differ
from branchiomeric muscles, and there is evidence that branchiomeric muscle
development varies among the different BAs
(Dong et al., 2006;
Kelly et al., 2004).
A previous study in chick embryos demonstrated that signals from the dorsal
neural tube (e.g. Wnt1 and Wnt3a) block cardiogenesis in the adjacent CPM
(Tzahor and Lassar, 2001). We
further demonstrated in vivo, also in chick embryos, that a subset of CPM
cells contributes to both myocardial and endocardial cell populations within
the cardiac OFT (Tirosh-Finkel et al.,
2006). These two studies revealed that CPM cells contribute to
both cardiac and skeletal muscle lineages, and illustrate the plasticity of
these cells during embryogenesis. In accordance with these results, recent
studies involving various transgenic mouse lines have demonstrated an overlap
in the progenitor populations contributing to branchiomeric and cardiac muscle
(Dong et al., 2006;
Kelly et al., 2001;
Verzi et al., 2005) (reviewed
by Grifone and Kelly,
2007).
The LIM homeodomain protein Islet1 (Isl1) stands at a nodal point in the
self-renewal, differentiation and lineage specification of distinct
cardiovascular precursors, and is a major player in the second heart field
lineage during embryogenesis (Cai et al.,
2003; Laugwitz et al.,
2005; Moretti et al.,
2006). This transcription factor marks undifferentiated
progenitors of the SHF; its expression is downregulated with differentiation
(Cai et al., 2003). Genetic
removal of Isl1 in mice showed that Bmp4 (as well as other
Bmp and Fgf family members) is a target of Isl1 in the AHF
(Cai et al., 2003). We
demonstrated in chick embryos that Bmp4 induces Isl1 expression in
the CPM, while blocking its expression in neuronal tissues
(Tirosh-Finkel et al., 2006).
More recently, it has been shown in mice that β-catenin directly targets
and activates Isl1 expression in the AHF
(Lin et al., 2007).
In the present study, we characterized the nature of the Isl1+ cardio-craniofacial splanchnic mesoderm, using several lineage-tracing and gene expression techniques in both chick and mouse embryos. At both the cellular and molecular levels, the cardio-craniofacial mesoderm can be divided into two compartments: the CPM and splanchnic mesoderm (SpM), part of which comprises the AHF. Following linear heart tube stages, we found that Isl1+/SpM cells contribute to the distal part of the pharyngeal (branchial) mesoderm, as well as to the cardiac OFT. Molecular and lineage analyses of the head musculature in chick and mouse embryos demonstrated distinct molecular and developmental programs for CPM and Isl1+ SpM-derived branchiomeric muscles. Furthermore, we demonstrate that the Wnt/β-catenin pathway regulates Isl1 (and Nkx2.5) protein expression, presumably by fine-tuning boundary formation within the cardio-craniofacial mesoderm.
|
MATERIALS AND METHODS |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
).
Whole-mount in situ hybridization
Whole-mount in situ hybridization was performed using digoxigenin
(dig)-labeled antisense riboprobes synthesized from total cDNA. A detailed
protocol, as well as specific primers for cDNA probes, are available upon
request.
Double-fluorescence in situ hybridization (FISH) on paraffin sections
Paraffin sections were hybridized with two RNA probes, one labeled with
dig-UTP and the other with fluorescein-UTP. Post-hybridization, each probe was
developed separately using the FITC/Cy3 tyramide amplification system (Perkin
Elmer).
Sectioning and histology
For cryosections, embryos were incubated overnight in 20% sucrose in PBS,
and then embedded in 7.5% gelatin, 15% sucrose in PBS. Blocks were trimmed and
frozen and then sectioned at 20 µm.
Lineage tracing and dye injection
DiI/DiO (D282, C275, Molecular Probes) labeling experiments were performed
on St. 8 embryos as described previously
(Tirosh-Finkel et al.,
2006).
Implantation of Fz8-CRD-IgG beads
Affi-Gel blue gel beads (150-300 µm; Bio-Rad) were soaked in 200
ng/µl Fz8-CRD-IgG or BSA prior to in vivo implantation into the CPM of St.
8-9 embryos.
Mutant mice and lacZ staining
Isl1-Cre and Rosa26R strains were crossed to generate
embryos at E10.5, 12.5 and 16.5, as previously described
(Yang et al., 2006).
β-gal staining was performed as previously described
(Moretti et al., 2006).
Embryos were embedded in paraffin and 8 µm sections were counterstained
with Nuclear Fast Red.
Immunofluorescence staining
Sections were blocked with 5% goat serum, 1% BSA in PBS prior to incubation
with the primary antibody: Nkx2.5 (Santa-Cruz), β-galactosidase (Sigma),
chick MyoD (a gift from Prof. Yablonka-Reuveni, University of Washington
School of Medicine, Seattle, WA), Myf5 (a gift from Dr Bruce Paterson, NIH,
Bethesda, MD), Isl1, Pax7 and MF20 (DSHB). Secondary antibodies used were Cy3
or Cy2-conjugated-anti-mouse or anti-rabbit IgG (Jackson ImmunoResearch).
Electroporation
Detailed protocols are available upon request.
|
RESULTS |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
To further define the boundaries of distinct mesodermal compartments, we
used double-fluorescence in situ hybridization (FISH)
(Denkers et al., 2004) on
sectioned embryos (Fig. 1E-I).
Our results confirmed that Nkx2.5 and Isl1
(Fig. 1E-E''), as well as
Fgf10 (Fig.
1F-F''), are co-expressed throughout the SpM. The boundaries
of the undifferentiated SpM, which demarcate the AHF/SHF, are delineated by
the CPM marker Cyp26c1 (Fig.
1G-G'') (Bothe and
Dietrich, 2006) and by the cardiac differentiation marker
Gata4 (Fig.
1H-H''). Tbx5, like Gata4, was found to be
restricted to the differentiating myocardial cells in the lateral SpM, whereas
Tbx20 was also expressed in the AHF/SpM
(Fig. 1I-I''). Taken
together, our molecular analyses enabled us to delineate the boundaries
between the CPM, undifferentiated SpM progenitors of the AHF/SHF, and
differentiating cardiac cells in the SpM of St. 8 chick embryos.
|
Because Isl1 has been shown to be a marker of the AHF/SHF in both
mouse (Cai et al., 2003;
Moretti et al., 2006) and
chick (Tirosh-Finkel et al.,
2006) models, we performed immunofluorescence analysis for this
protein at relevant stages of cardiac development in chick embryos
(Fig. 2). Transverse sections
of the head and heart regions were taken at three axial levels and stained
with Isl1 antibody. In general, Isl1 expression in all three germ layers
matched the in situ hybridization patterns
[Fig. 1 and Tirosh-Finkel et
al. (Tirosh-Finkel et al.,
2006)]. At St. 8, Isl1 was detected throughout the SpM, including
the dorsomedial aspect (Fig.
2A-C'), whereas at St. 12 and 18 its mesodermal expression
was largely excluded from cardiac myocardium. At St. 12, Isl1 was observed in
the SpM underneath the ventral pharynx, as well as in the pharyngeal endoderm
(Fig. 2D-F'). Notably, at
St. 18, Isl1 expression was detected in the distal part of the myogenic core
of the first and second BAs (BA1-2) and surrounding the aortic sac
(Fig. 2G-I'). The latter
findings point to the possible involvement of Isl1 in skeletal muscle
progenitors.
Fate mapping of the Isl1 and Nkx2.5-expressing SpM cells in chick embryos
We previously demonstrated in chick embryos that DiI labeling of the CPM at
St. 8 (prior to delamination of cranial neural crest cells) resulted in the
presence of labeled cells in both BA1 and in the cardiac OFT
[Fig. 3A,A' and
Tirosh-Finkel et al. (Tirosh-Finkel et
al., 2006)]. Likewise, both the OFT and BA1 were labeled when DiI
was injected into Isl1- and Nkx2.5-expressing medial SpM
(Fig. 3A'',A''').
This experiment indicates that Nkx2.5/Isl1-expressing
undifferentiated SpM cells migrate to both BA1 and the cardiac OFT.
We next labeled both CPM (DiI, red) and Isl1- and Nkx2.5-expressing undifferentiated SpM (DiO, green) at St. 8 (Fig. 3B-G; the section in B' indicates that labeling was indeed restricted to the CPM and SpM). At St. 11, DiO-labeled SpM cells were detected in the OFT, whereas DiI-labeled CPM cells remained adjacent to the neural tube (Fig. 3C-C''). Sections of the BA region at St. 12 revealed how CPM and SpM cells populated the myogenic core of the developing BA1: cells from CPM were detected within the proximal BA, whereas SpM cells filled the distal BA (Fig. 3D'). At this stage, both CPM and SpM cells were observed within the OFT (Fig. 3D''). At St. 16, SpM cells (DiO, green) filled the most-distal region of the myogenic core within BA1, whereas CPM cells (DiI, red) filled the proximal region of the myogenic core (Fig. 3E-G). To investigate the nature of labeled cells from the SpM, DiO was injected into the SpM, and labeled embryos were subsequently stained for Isl1 and Nkx2.5 (Fig. 3F,G, respectively). These markers were co-expressed with the fluorescent dye in distal BA1. Taken together, these results indicate that CPM and undifferentiated Isl1+ and Nkx2.5+ SpM cells contribute to both the cardiac OFT and the mesodermal core of BA1 in a distinct spatial and temporal manner.
|
We then explored the molecular and anatomical characteristics of CPM- and
SpM-derived branchiomeric muscles (Fig.
4). Dye labeling of either proximal or distal BA1 myogenic
populations at St. 15, followed by immunostaining for MyoD at St. 26, revealed
that the mandibular adductor muscle in birds (equivalent to the masseter in
mammals) is derived from the proximal region of the myogenic core, whereas
distal BA1 myoblasts form the intermandibular muscle
(Fig. 1A-A''') (see also
Marcucio and Noden, 1999;
Noden et al., 1999). At St.
20, Myf5 and Isl1 double staining in BA1 matched the proximal/distal
regionalization of CPM and SpM cells in the myogenic core
(Fig. 4B,B'; compare with
Fig. 3E-E'). Notably, at
this stage, Pax7 and Myf5 co-expression was detected in the dorsal/proximal
region of the myogenic core, but not in the distal, Isl1+ region
(Fig. 4B'').
We therefore wanted to check whether these two BA1-derived muscles differ
molecularly. Strikingly, we found that at St. 26 [embryonic day 5 (E5)], the
mandibular adductor complex expressed Myf5, Pax7, myosin heavy chain (MHC)
(Fig. 4D-E') and MyoD
(not shown). By contrast, the intermandibular muscle anlagen (derived from the
SpM, Fig. 4A'''),
expressed Isl1, Myf5 (Fig.
4E',E'') and MyoD
(Fig. 4F',F''; note
that Isl1 and MyoD are not expressed in the same cells). Pax7 expression in
the intermandibular muscle anlagen was absent and MHC expression was
significantly delayed, compared with the mandibular adductor or the adjacent
genioglossal muscle that connects the tongue to the mandible
(Fig. 4F''',G''') and
is derived from myoblasts in the third BA
(Marcucio and Noden, 1999). At
E7 (St. 31) of chick embryonic development, Pax7 and MHC expression was
observed in all muscles at the expense of Isl1, which was diminished
(Fig. 4H-H'''). Thus, Isl1
expression in the (SpM-derived) intermandibular anlagen correlates with its
delayed differentiation, similar to Isl1+ cardioblasts in the AHF
(Fig. 2). These novel findings
suggest that there are distinct developmental programs for CPM- and
SpM-derived branchiomeric muscles (as summarized in
Fig. 4C).
To assess the contribution of Isl1+ cells to the head
musculature in mouse embryos, we employed the Cre-loxP system to genetically
mark Isl1 progenitors by crossing Isl1-Cre mice
(Yang et al., 2006) with the
transgenic reporter line R26R. Staining for β-galactosidase
(β-gal) in whole-mount and sectioned Isl1-Cre;R26R embryos
(E10.5) revealed a contribution of Isl1+ progenitors to
the myogenic core of BA1 (Fig.
5A,A'). Double staining with anti-β-gal and MyoD
antibodies was performed on Isl1-Cre;R26R embryos (E12.5) to further
demonstrate the contribution of the Isl1+ precursors to
branchiomeric muscles, but not to the extraocular, tongue or trunk muscles
(data not shown).
In order to carefully assess the myogenic contribution of Isl1+ cells in mice, we analyzed E16.5 Isl1-Cre;R26R sectioned embryos (Fig. 5B-F). β-gal staining was strongly detected in distinct branchiomeric muscles, such as stylohyoid muscle (Fig. 5D), mylohyoid muscle, posterior digastric muscle, extrinsic laryngeal muscles (e.g. inferior constrictor, Fig. 5E), distal facial muscles (e.g. buccinator) and facial subcutaneous muscles (data not shown). Staining was also detected in other tissues, including cranial motoneurons and ganglia, salivary glands, the esophagus and connective tissues (Fig. 5C). We also detected partial β-gal staining in the mastication muscles that control the movement of the mandible, the masseter and pterygoid (Fig. 5F).
|
The Wnt/β-catenin pathway regulates heart field boundaries, differentiation and morphogenesis
Previous studies in chick and frog embryos suggested that members of the
canonical Wnt signaling pathway can act as repressors of cardiac
differentiation (Brott and Sokol,
2005; Foley and Mercola,
2005; Marvin et al.,
2001; Schneider and Mercola,
2001; Tzahor and Lassar,
2001). Recent studies in mouse and zebrafish embryos, as well as
in embryonic stem cells, have shed new light on the regulation of
cardiogenesis by the Wnt/β-catenin pathway
(Ai et al., 2007;
Cohen et al., 2007;
Kwon et al., 2007;
Lin et al., 2007;
Qyang et al., 2007;
Ueno et al., 2007). Ablation
of β-catenin in mice resulted in embryonic lethality, which was
attributed to defects in second heart field derivatives: the right ventricular
chamber, OFT and pharyngeal mesoderm (reviewed by
Tzahor, 2007).
The molecular and cellular characterization of distinct mesodermal fields in chick embryos enabled us to explore the role of the Wnt/β-catenin pathway during early and late looping stages. Utilizing an in ovo electroporation system in chick embryos, control GFP or Wnt3a-IRES-GFP constructs were electroporated at primitive streak stages to test the effects of the Wnt/β-catenin pathway on cardiac markers (Fig. 6A). Unilateral electroporation of Wnt3a into St. 8 chick embryos resulted in the almost complete repression of Tbx5, Nkx2.5 and Gata4 in differentiated cardiac crescent/SpM cells (Fig. 6B-D, respectively).
|
). We then tested how inhibition of the Wnt/β-catenin pathway affects cardiogenesis (Fig. 7). In vivo electroporation of the Wnt antagonists sFrp2 and sFrp3 into the surface ectoderm (Fig. 7A,B) caused an expansion in the expression domains of both Nkx2.5 and Isl1 (Fig. 7C,D). Furthermore, implantation of beads soaked with a purified Fz8-IgG protein into the CPM of St. 8 embryos (Fig. 7E,F) resulted in the dramatic induction of both Nkx2.5 (Fig. 7G-H') and Isl1 (Fig. 7I,I') within BA1 by St. 14. Taken together, these findings indicate that in chick embryos, the Wnt/β-catenin pathway can block cardiac and skeletal muscle differentiation in vivo; moreover, antagonists of this pathway induced Isl1 and Nkx2.5 expression in the SpM of both the AHF and BA mesoderm.
|
|
DISCUSSION |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Molecular characterization of the heart fields in chick and mouse embryos
Despite accumulating evidence concerning the subdivision of cardiac
progenitor populations into distinct heart fields in the mouse, the exact
anatomical locations of these fields in other vertebrates remains unclear
(Abu-Issa and Kirby, 2007). In
the chick, we defined the AHF field as being located in the dorsomedial region
of the SpM in St. 8 embryos in agreement with the current model of two heart
fields in the mouse (Buckingham et al.,
2005; Srivastava,
2006), which is based on both molecular (Isl1, Nkx2.5, Fgf10,
Tbx20) and anatomical considerations
(Fig. 8A). In contrast to the
mouse, in which Isl1 and Fgf10 expression were shown to be
restricted to the dorsomedial domain of the cardiac crescent
(Cai et al., 2003;
Kelly et al., 2001), in the
chick, both genes are expressed throughout the cardiac crescent. However,
downregulation of these markers within differentiating cardiac cells occurs
during linear heart tube stages, as the heart begins to beat.
What is the relationship between the contribution of the CPM
(Tirosh-Finkel et al., 2006)
and AHF/SHF/SpM to the cardiac OFT? Although CPM cells migrate distally to the
BAs, where some of these cells infiltrate the AHF/SHF, each cell population
seems to contribute to the cardiac OFT in a distinct manner. The entrance of
AHF/SHF/SpM cells into the cardiac OFT precedes that of the CPM cells, which
also seem to follow a different migratory path. We propose that the
contributions of the CPM and AHF/SHF/SpM to the anterior pole of the heart are
distinct, both spatially and temporally.
Distinct mesodermal origins for branchiomeric muscles
Findings in mice already suggested that SpM cells contribute to both the
pharyngeal mesoderm and the cardiac OFT
(Dong et al., 2006;
Kelly et al., 2001;
Verzi et al., 2005). However,
the specific contribution of Isl1+ SpM cells to the distal part of
the myogenic core in BA1, and later to distinct branchiomeric muscles,
remained unclear. Our findings in the chick demonstrate that branchiomeric
skeletal muscles derive from both CPM and Isl1+/SpM
(Fig. 8C); furthermore, CPM-
and SpM-derived BA1 muscles are molecularly distinct.
Previous studies in chick embryos are consistent with the separation of
myoblasts in BA1 into proximal (mandibular adductor) and distal
(intermandibular) jaw muscles (Marcucio
and Noden, 1999; Noden et al.,
1999). Interestingly, Pax7 is expressed in CPM-but not SpM-derived
myoblasts, whereas Isl1 is expressed in the SpM-derived branchiomeric muscles.
Because MHC expression is delayed in SpM-derived Isl1-expressing myoblasts, we
suggest that it acts as a repressor of myogenic differentiation in a manner
similar to its expression in undifferentiated second heart field cells before
they enter the heart. It is tempting to speculate that Isl1 might also play a
role in the regulation of quiescence and self-renewal of satellite cells in
branchiomeric muscles, analogous to the role of Pax7 in trunk skeletal
muscles
Our lineage studies in both chick and mouse models provide a clear example of lineage heterogeneity within craniofacial muscles. In both species, Isl1+ SpM cells contribute to a set of branchiomeric muscles at the base of the mandible facilitating its opening: the intermandibular muscle in the chick, and the mylohyoid, stylohyoid, digastric and other (distal) facial muscles in the mouse. By contrast, there is a relatively minor contribution of Isl1+ cells to the mastication muscles in the mouse (masseter, pterygoid and temporalis) or to the mandibular adductor complex in the chick. Furthermore, in both species, the intrinsic and extrinsic muscles of the tongue (e.g. genioglossal) and extraocular muscles are not derived from the Isl1+ SpM lineage. The slightly broader contribution of the Isl1+ lineage to branchiomeric muscle, observed in the mouse, could result from differences in the lineage allocations between the two species. Similarly, the contribution of Isl1+ cells of the second heart field is broader in the mouse than that in the chick. Clearly, methodological and experimental differences affect lineage comparisons between chick and mouse models. In our R26R muscle lineage analyses in mice, it is important to appreciate that the fusion of a few β-gal+ myoblasts is likely to result in staining of the entire myofiber (e.g. masseter, pterygoid and temporalis, Fig. 5).
|
|
|
),
as well as capsulin and MyoR (Lu et al.,
2002), have been shown to act as upstream regulators of
branchiomeric muscle development. In capsulin/MyoR double mutants
(Lu et al., 2002), the
masseter, pterygoids and temporalis were missing, whereas the distal BA1
muscles (e.g. anterior digastric and mylohyoid, both derived from
Isl1+ cells, Fig. 5)
were not affected. Our findings in both chick and mouse experimental models,
which reveal that jaw muscles are composed of at least two distinct myogenic
lineages (CPM-derived and Isl1+ SpM-derived muscles), provide a
plausible developmental explanation for this unique muscle phenotype.
It was recently demonstrated in mice that Isl1/Nkx2.5/Flk1-positive cells
within the SpM are multipotent cardiovascular progenitors that give rise to
cardiac myocytes, smooth muscle and endothelial lineages within the heart
(Moretti et al., 2006;
Wu et al., 2006). We show that
Isl1+ cells represent multipotential progenitors of both
cardiovascular and skeletal muscle lineages.
Wnt/β-catenin signaling and its effect on cardiac and skeletal muscle development
We previously demonstrated in the chick that signals emanating from the
neural tube (that can be mimicked by Wnt1 and Wnt3a) block cardiogenesis in
the CPM (Tzahor and Lassar,
2001). These findings, and those of two other studies
(Marvin et al., 2001;
Schneider and Mercola, 2001),
suggest that Wnt/β-catenin signaling inhibits cardiogenesis during early
embryogenesis. A subsequent study (Foley
and Mercola, 2005) demonstrated that Wnt signaling must be
inhibited within the endoderm to induce secretion of an as yet unidentified
cardiogenic-inducing factor. In fact, numerous studies support the notion that
inhibition of the Wnt/β-catenin pathway is required for proper heart
development and repair (Barandon et al.,
2003; Brott and Sokol,
2005; Lickert et al.,
2002; Singh et al.,
2007), whereas other studies, mostly in cultured ES cells, suggest
that the opposite is true (Nakamura et
al., 2003).
Recent studies in mouse and zebrafish embryos, as well as in embryonic stem
cells, demonstrate that the Wnt/β-catenin pathway plays distinct, even
opposing, roles during various stages and within distinct tissues during
cardiac development (reviewed by Tzahor,
2007). The new loss-of-function studies of canonical Wnt signaling
in the mouse (Ai et al., 2007;
Cohen et al., 2007;
Kwon et al., 2007;
Lin et al., 2007;
Qyang et al., 2007;
Ueno et al., 2007) provide
compelling evidence that this pathway is required within cardiac progenitors
and differentiating cardiac cells for the development of the second heart
field (including AHF cells) and its derivatives: the right ventricular
chamber, OFT and pharyngeal mesoderm. These studies further demonstrate that
Wnt signaling stimulates the proliferation of cardiac progenitors during mouse
cardiogenesis.
Using electroporation of Wnt ligands or Wnt inhibitors in chick embryos, we observed either the inhibition of cardiac and skeletal muscle differentiation markers, or the expansion of Isl1 and Nkx2.5, respectively. Similarly, bead implantation of a Wnt inhibitor into the CPM resulted in increased expression of Nkx2.5 and Isl1 within the SpM-derived myogenic mesoderm of BA1. These results suggest that canonical Wnt signaling can inhibit cardiac and cranial muscle differentiation, which is consistent with findings in mice demonstrating that continuous Wnt signaling prolongs the progenitor state and interferes with differentiation during cardiogenesis.
The cardio-craniofacial mesoderm
Taken together, our past and present studies clearly demonstrate that the
cardio-craniofacial mesoderm is tightly regulated by both positive and
negative cues from surrounding tissues
(Rinon et al., 2007;
Tirosh-Finkel et al., 2006;
Tzahor et al., 2003;
Tzahor and Lassar, 2001). Our
findings highlight the heterogeneity of developmental programming among
cranial muscles, and confirm that craniofacial myogenesis is developmentally
linked to cardiac development (this study)
(Tirosh-Finkel et al., 2006;
Tzahor and Lassar, 2001)
(reviewed by Grifone and Kelly,
2007), suggesting that these tissues share a common evolutionary
origin.
The striking parallel between a subset of branchiomeric muscles and the
transcriptional networks involved in heart development (this study)
(Dong et al., 2006;
Kelly et al., 2001;
Verzi et al., 2005) is
actually seen across vast phylogenetic distances. Nematodes do not possess a
heart, yet their pharyngeal muscle contracts like a heart and exhibits
electrical activity similar to that of mammalian cardiomyocytes. Moreover, it
has been shown that the development of the pharyngeal muscle in nematodes, and
of cardiac muscle in vertebrates and insects, is regulated by the homeobox
gene Nkx2.5 (Haun et al.,
1998). Thus, unlike skeletal muscles in the trunk, head muscles
are likely to have evolved from an ancestral developmental program that gave
rise to a contractile tube used for feeding and circulation. Insights into the
genetic circuits that drive the evolution and development of heart and
craniofacial muscles might shed light on general principles of organogenesis,
as well as on the molecular basis of cardiovascular and craniofacial
myopathies in humans.
Supplementary material
Supplementary material for this article is available at
http://dev.biologists.org/cgi/content/full/135/4/647/DC1
|
ACKNOWLEDGMENTS |
|---|
|
REFERENCES |
|---|
|
TOP
SUMMARY
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES |
|---|
Abu-Issa, R. and Kirby, M. L. (2007). Heart
field: from mesoderm to heart tube. Annu. Rev. Cell Dev.
Biol. 23,45
-68.[CrossRef][Medline]
Ai, D., Fu, X., Wang, J., Lu, M. F., Chen, L., Baldini, A.,
Klein, W. H. and Martin, J. F. (2007). Canonical Wnt
signaling functions in second heart field to promote right ventricular growth.
Proc. Natl. Acad. Sci. USA
104,9319
-9324.
Barandon, L., Couffinhal, T., Ezan, J., Dufourcq, P., Costet,
P., Alzieu, P., Leroux, L., Moreau, C., Dare, D. and Duplaa, C.
(2003). Reduction of infarct size and prevention of cardiac
rupture in transgenic mice overexpressing FrzA.
Circulation 108,2282
-2289.
Bellairs, R. and Osmond. M. (1998).
The Atlas of Chick Development. London: Academic
Press.
Black, B. L. (2007). Transcriptional pathways
in second heart field development. Semin. Cell Dev.
Biol. 18,67
-76.[CrossRef][Medline]
Bothe, I. and Dietrich, S. (2006). The
molecular setup of the avian head mesoderm and its implication for
craniofacial myogenesis. Dev. Dyn.
235,2845
-2860.[CrossRef][Medline]
Bothe, I., Ahmed, M. U., Winterbottom, F. L., von Scheven, G.
and Dietrich, S. (2007). Extrinsic versus intrinsic cues in
avian paraxial mesoderm patterning and differentiation. Dev.
Dyn. 236,2397
-2409.[CrossRef][Medline]
Brott, B. K. and Sokol, S. Y. (2005). A
vertebrate homolog of the cell cycle regulator Dbf4 is an inhibitor of Wnt
signaling required for heart development. Dev. Cell
8, 703-715.[CrossRef][Medline]
Buckingham, M., Meilhac, S. and Zaffran, S.
(2005). Building the mammalian heart from two sources of
myocardial cells. Nat. Rev. Genet.
6, 826-835.[CrossRef][Medline]
Cai, C. L., Liang, X., Shi, Y., Chu, P. H., Pfaff, S. L., Chen,
J. and Evans, S. (2003). Isl1 identifies a cardiac progenitor
population that proliferates prior to differentiation and contributes a
majority of cells to the heart. Dev. Cell
5, 877-889.[CrossRef][Medline]
Cohen, E. D., Wang, Z., Lepore, J. J., Lu, M. M., Taketo, M. M.,
Epstein, D. J. and Morrisey, E. E. (2007). Wnt/beta-catenin
signaling promotes expansion of Isl-1-positive cardiac progenitor cells
through regulation of FGF signaling. J. Clin. Invest.
117,1794
-1804.[CrossRef][Medline]
Denkers, N., Garcia-Villalba, P., Rodesch, C. K., Nielson, K. R.
and Mauch, T. J. (2004). FISHing for chick genes:
triple-label whole-mount fluorescence in situ hybridization detects
simultaneous and overlapping gene expression in avian embryos. Dev.
Dyn. 229,651
-657.[CrossRef][Medline]
Dong, F., Sun, X., Liu, W., Ai, D., Klysik, E., Lu, M. F.,
Hadley, J., Antoni, L., Chen, L., Baldini, A. et al. (2006).
Pitx2 promotes development of splanchnic mesoderm-derived branchiomeric
muscle. Development 133,4891
-4899.
Emery, A. E. (2002). The muscular dystrophies.
Lancet 359,687
-695.[CrossRef][Medline]
Foley, A. C. and Mercola, M. (2005). Heart
induction by Wnt antagonists depends on the homeodomain transcription factor
Hex. Genes Dev. 19,387
-396.
Garry, D. J. and Olson, E. N. (2006). A common
progenitor at the heart of development. Cell
127,1101
-1104.[CrossRef][Medline]
Grifone, R. and Kelly, R. G. (2007). Heartening
news for head muscle development. Trends Genet.
23,365
-369.[CrossRef][Medline]
Hamburger, V. and Hamilton, H. L. (1992). A
series of normal stages in the development of the chick embryo.
Dev. Dyn. 195,231
-272.[Medline]
Haun, C., Alexander, J., Stainier, D. Y. and Okkema, P. G.
(1998). Rescue of Caenorhabditis elegans pharyngeal development
by a vertebrate heart specification gene. Proc. Natl. Acad. Sci.
USA 95,5072
-5075.
Hutson, M. R. and Kirby, M. L. (2003). Neural
crest and cardiovascular development: a 20-year perspective. Birth
Defects Res. C Embryo Today 69,2
-13.[CrossRef][Medline]
Kaufman, M. (1992). The Atlas of
Mouse Development. London: Academic Press.
Kelly, R. G., Brown, N. A. and Buckingham, M. E.
(2001). The arterial pole of the mouse heart forms from
Fgf10-expressing cells in pharyngeal mesoderm. Dev.
Cell 1,435
-440.[CrossRef][Medline]
Kelly, R. G., Jerome-Majewska, L. A. and Papaioannou, V. E.
(2004). The del22q11.2 candidate gene Tbx1 regulates
branchiomeric myogenesis. Hum. Mol. Genet.
13,2829
-2840.
Kwon, C., Arnold, J., Hsiao, E. C., Taketo, M. M., Conklin, B.
R. and Srivastava, D. (2007). Canonical Wnt signaling is a
positive regulator of mammalian cardiac progenitors. Proc. Natl.
Acad. Sci. USA 104,10894
-10899.
Laugwitz, K. L., Moretti, A., Lam, J., Gruber, P., Chen, Y.,
Woodard, S., Lin, L. Z., Cai, C. L., Lu, M. M., Reth, M. et al.
(2005). Postnatal isl1+ cardioblasts enter fully differentiated
cardiomyocyte lineages. Nature
433,647
-653.[CrossRef][Medline]
Lickert, H., Kutsch, S., Kanzler, B., Tamai, Y., Taketo, M. M.
and Kemler, R. (2002). Formation of multiple hearts in mice
following deletion of beta-catenin in the embryonic endoderm. Dev.
Cell 3,171
-181.[CrossRef][Medline]
Lin, L., Cui, L., Zhou, W., Dufort, D., Zhang, X., Cai, C. L.,
Bu, L., Yang, L., Martin, J., Kemler, R. et al. (2007).
beta-Catenin directly regulates Islet1 expression in cardiovascular
progenitors and is required for multiple aspects of cardiogenesis.
Proc. Natl. Acad. Sci. USA
104,9313
-9318.
Lu, J. R., Bassel-Duby, R., Hawkins, A., Chang, P., Valdez, R.,
Wu, H., Gan, L., Shelton, J. M., Richardson, J. A. and Olson, E. N.
(2002). Control of facial muscle development by MyoR and
capsulin. Science 298,2378
-2381.
Marcucio, R. S. and Noden, D. M. (1999).
Myotube heterogeneity in developing chick craniofacial skeletal muscles.
Dev. Dyn. 214,178
-194.[CrossRef][Medline]
Marvin, M. J., Di Rocco, G., Gardiner, A., Bush, S. M. and
Lassar, A. B. (2001). Inhibition of Wnt activity induces
heart formation from posterior mesoderm. Genes Dev.
15,316
-327.
Mjaatvedt, C. H., Nakaoka, T., Moreno-Rodriguez, R., Norris, R.
A., Kern, M. J., Eisenberg, C. A., Turner, D. and Markwald, R. R.
(2001). The outflow tract of the heart is recruited from a novel
heart-forming field. Dev. Biol.
238,97
-109.[CrossRef][Medline]
Moretti, A., Caron, L., Nakano, A., Lam, J. T., Bernshausen, A.,
Chen, Y., Qyang, Y., Bu, L., Sasaki, M., Martin-Puig, S. et al.
(2006). Multipotent embryonic isl1+ progenitor cells lead to
cardiac, smooth muscle, and endothelial cell diversification.
Cell 127,1151
-1165.[CrossRef][Medline]
Nakamura, T., Sano, M., Songyang, Z. and Schneider, M. D.
(2003). A Wnt- and beta-catenin-dependent pathway for mammalian
cardiac myogenesis. Proc. Natl. Acad. Sci. USA
100,5834
-5839.
Noden, D. M. (1983). The role of the neural
crest in patterning of avian cranial skeletal, connective, and muscle tissues.
Dev. Biol. 96,144
-165.[CrossRef][Medline]
Noden, D. M. and Francis-West, P. (2006). The
differentiation and morphogenesis of craniofacial muscles. Dev.
Dyn. 235,1194
-1218.[CrossRef][Medline]
Noden, D. M., Marcucio, R., Borycki, A. G. and Emerson, C. P.,
Jr (1999). Differentiation of avian craniofacial muscles. I.
Patterns of early regulatory gene expression and myosin heavy chain synthesis.
Dev. Dyn. 216,96
-112.[CrossRef][Medline]
Qyang, Y., Martin-Puig, S., Chiravuri, M., Chen, S., Xu, H., Bu,
L., Jiang, X., Lin, L., Granger, A., Moretti, A. et al.
(2007). The renewal and differentiation of Isl1+ cardiovascular
progenitors are controlled by a Wnt/β-catenin pathway. Cell
Stem Cell 1,165
-179.[CrossRef][Medline]
Rinon, A., Lazar, S., Marshall, H., Buchmann-Moller, S.,
Neufeld, A., Elhanany-Tamir, H., Taketo, M. M., Sommer, L., Krumlauf, R. and
Tzahor, E. (2007). Cranial neural crest cells regulate head
muscle patterning and differentiation during vertebrate embryogenesis.
Development 134,3065
-3075.
Schneider, V. A. and Mercola, M. (2001). Wnt
antagonism initiates cardiogenesis in Xenopus laevis. Genes
Dev. 15,304
-315.
Singh, A. M., Li, F. Q., Hamazaki, T., Kasahara, H., Takemaru,
K. and Terada, N. (2007). Chibby, an antagonist of the
Wnt/beta-catenin pathway, facilitates cardiomyocyte differentiation of murine
embryonic stem cells. Circulation
115,617
-626.
Srivastava, D. (2006). Making or breaking the
heart: from lineage determination to morphogenesis.
Cell 126,1037
-1048.[CrossRef][Medline]
Tirosh-Finkel, L., Elhanany, H., Rinon, A. and Tzahor, E.
(2006). Mesoderm progenitor cells of common origin contribute to
the head musculature and the cardiac outflow tract.
Development 133,1943
-1953.
Trainor, P. A., Tan, S. S. and Tam, P. P.
(1994). Cranial paraxial mesoderm: regionalisation of cell fate
and impact on craniofacial development in mouse embryos.
Development 120,2397
-2408.
Tzahor, E. (2007). Wnt/beta-catenin signaling
and cardiogenesis: timing does matter. Dev. Cell
13, 10-13.[CrossRef][Medline]
Tzahor, E. and Lassar, A. B. (2001). Wnt
signals from the neural tube block ectopic cardiogenesis. Genes
Dev. 15,255
-260.
Tzahor, E., Kempf, H., Mootoosamy, R. C., Poon, A. C., Abzhanov,
A., Tabin, C. J., Dietrich, S. and Lassar, A. B. (2003).
Antagonists of Wnt and BMP signaling promote the formation of vertebrate head
muscle. Genes Dev. 17,3087
-3099.
Ueno, S., Weidinger, G., Osugi, T., Kohn, A. D., Golob, J. L.,
Pabon, L., Reinecke, H., Moon, R. T. and Murry, C. E. (2007).
Biphasic role for Wnt/beta-catenin signaling in cardiac specification in
zebrafish and embryonic stem cells. Proc. Natl. Acad. Sci.
USA 104,9685
-9690.
Verzi, M. P., McCulley, D. J., De Val, S., Dodou, E. and Black,
B. L. (2005). The right ventricle, outflow tract, and
ventricular septum comprise a restricted expression domain within the
secondary/anterior heart field. Dev. Biol.
287,134
-145.[CrossRef][Medline]
Wachtler, F. and Jacob, M. (1986). Origin and
development of the cranial skeletal muscles. Bibl.
Anat. 29,24
-46.[Medline]
Waldo, K. L., Kumiski, D. H., Wallis, K. T., Stadt, H. A.,
Hutson, M. R., Platt, D. H. and Kirby, M. L. (2001).
Conotruncal myocardium arises from a secondary heart field.
Development 128,3179
-3188.[Medline]
Wu, S. M., Fujiwara, Y., Cibulsky, S. M., Clapham, D. E., Lien,
C. L., Schultheiss, T. M. and Orkin, S. H. (2006).
Developmental origin of a bipotential myocardial and smooth muscle cell
precursor in the mammalian heart. Cell
127,1137
-1150.[CrossRef][Medline]
Yang, L., Cai, C. L., Lin, L., Qyang, Y., Chung, C., Monteiro,
R. M., Mummery, C. L., Fishman, G. I., Cogen, A. and Evans, S.
(2006). Isl1Cre reveals a common Bmp pathway in heart and limb
development. Development
133,1575
-1585.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati 
Twitter What's this?
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
