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Wnt signaling interacts with bmp and edn1 to regulate dorsal-ventral patterning and growth of the craniofacial skeleton.

Alexander C, Piloto S, Le Pabic P, Schilling TF - PLoS Genet. (2014)

Bottom Line: These D-V patterning defects resemble the phenotypes of zebrafish embryos lacking Bmp or Edn1 signaling, and overexpression of dntcf3 dramatically reduces expression of a subset of Bmp receptors in the arches.Addition of ectopic BMP (or EDN1) protein partially rescues ventral development and expression of dlx3b, dlx5a, and msxe in Wnt signaling-deficient embryos, but surprisingly does not rescue hand2 expression.Similarly, heat-shocked dkk1+ embryos exhibit ventral arch reductions, but also have mandibular clefts at the ventral midline not seen in dntcf3+ embryos.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America.

ABSTRACT
Craniofacial development requires signals from epithelia to pattern skeletogenic neural crest (NC) cells, such as the subdivision of each pharyngeal arch into distinct dorsal (D) and ventral (V) elements. Wnt signaling has been implicated in many aspects of NC and craniofacial development, but its roles in D-V arch patterning remain unclear. To address this we blocked Wnt signaling in zebrafish embryos in a temporally-controlled manner, using transgenics to overexpress a dominant negative Tcf3, (dntcf3), (Tg(hsp70I:tcf3-GFP), or the canonical Wnt inhibitor dickkopf1 (dkk1), (Tg(hsp70i:dkk1-GFP) after NC migration. In dntcf3 transgenics, NC cells in the ventral arches of heat-shocked embryos show reduced proliferation, expression of ventral patterning genes (hand2, dlx3b, dlx5a, msxe), and ventral cartilage differentiation (e.g. lower jaws). These D-V patterning defects resemble the phenotypes of zebrafish embryos lacking Bmp or Edn1 signaling, and overexpression of dntcf3 dramatically reduces expression of a subset of Bmp receptors in the arches. Addition of ectopic BMP (or EDN1) protein partially rescues ventral development and expression of dlx3b, dlx5a, and msxe in Wnt signaling-deficient embryos, but surprisingly does not rescue hand2 expression. Thus Wnt signaling provides ventralizing patterning cues to arch NC cells, in part through regulation of Bmp and Edn1 signaling, but independently regulates hand2. Similarly, heat-shocked dkk1+ embryos exhibit ventral arch reductions, but also have mandibular clefts at the ventral midline not seen in dntcf3+ embryos. Dkk1 is expressed in pharyngeal endoderm, and cell transplantation experiments reveal that dntcf3 must be overexpressed in pharyngeal endoderm to disrupt D-V arch patterning, suggesting that distinct endodermal roles for Wnts and Wnt antagonists pattern the developing skeleton.

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Model for the role of Wnt in dorsal-ventral arch patterning.(A) Diagrams illustrating regulation of expression of dorsal-ventral (D-V) arch patterning genes in the skeletogenic neural crest at 24 hpf (colored regions) by Bmp and Edn1 signals from the pharyngeal ectoderm and Wnt responses in the pharyngeal endoderm. Each arch is subdivided into ventral (blue), intermediate (dark green), and dorsal (light green) domains, which correspond to eventual dorsal-intermediate-ventral cartilage identities. Arrows indicate inductive influences by each signal on target genes. The yellow arrow indicates an unknown ventralizing signal X from the endoderm induced in response to Wnt. (B) Diagrams illustrating regulation of Bmp receptor expression along the D-V axis at 24 hpf (colored diagonal bars) by Wnt, Bmp and Edn1.
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pgen-1004479-g009: Model for the role of Wnt in dorsal-ventral arch patterning.(A) Diagrams illustrating regulation of expression of dorsal-ventral (D-V) arch patterning genes in the skeletogenic neural crest at 24 hpf (colored regions) by Bmp and Edn1 signals from the pharyngeal ectoderm and Wnt responses in the pharyngeal endoderm. Each arch is subdivided into ventral (blue), intermediate (dark green), and dorsal (light green) domains, which correspond to eventual dorsal-intermediate-ventral cartilage identities. Arrows indicate inductive influences by each signal on target genes. The yellow arrow indicates an unknown ventralizing signal X from the endoderm induced in response to Wnt. (B) Diagrams illustrating regulation of Bmp receptor expression along the D-V axis at 24 hpf (colored diagonal bars) by Wnt, Bmp and Edn1.

Mentions: We show that Wnt signaling promotes proliferation and provides ventral-intermediate patterning cues to NC cells in the pharyngeal arches by participating in a regulatory network with Edn1 and Bmp (Fig. 9). By overexpressing Dkk1 or dnTcf3 to disrupt Wnt signaling, we show that Wnt promotes expression of ventral (hand2) and ventral-intermediate genes (dlx3b, dlx5a, msxe) and their corresponding skeletal derivatives, and acts upstream or in parallel to the ventralizing activities of Edn1 and Bmp. Unlike Edn1 and Bmp, however, our chimeric analyses suggest that direct responses to Wnt signaling occur in the pharyngeal endoderm, which also expresses dkk1. This endoderm must secondarily produce as yet unknown signals important for D-V patterning, which regulate the competence of NC cells to respond to Bmp signaling, in part by transcriptionally regulating Bmp receptors. Overexpression of dkk1 also causes a unique midline clefting of the mandible, which we suggest reflects a role in formation of the mouth.


Wnt signaling interacts with bmp and edn1 to regulate dorsal-ventral patterning and growth of the craniofacial skeleton.

Alexander C, Piloto S, Le Pabic P, Schilling TF - PLoS Genet. (2014)

Model for the role of Wnt in dorsal-ventral arch patterning.(A) Diagrams illustrating regulation of expression of dorsal-ventral (D-V) arch patterning genes in the skeletogenic neural crest at 24 hpf (colored regions) by Bmp and Edn1 signals from the pharyngeal ectoderm and Wnt responses in the pharyngeal endoderm. Each arch is subdivided into ventral (blue), intermediate (dark green), and dorsal (light green) domains, which correspond to eventual dorsal-intermediate-ventral cartilage identities. Arrows indicate inductive influences by each signal on target genes. The yellow arrow indicates an unknown ventralizing signal X from the endoderm induced in response to Wnt. (B) Diagrams illustrating regulation of Bmp receptor expression along the D-V axis at 24 hpf (colored diagonal bars) by Wnt, Bmp and Edn1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109847&req=5

pgen-1004479-g009: Model for the role of Wnt in dorsal-ventral arch patterning.(A) Diagrams illustrating regulation of expression of dorsal-ventral (D-V) arch patterning genes in the skeletogenic neural crest at 24 hpf (colored regions) by Bmp and Edn1 signals from the pharyngeal ectoderm and Wnt responses in the pharyngeal endoderm. Each arch is subdivided into ventral (blue), intermediate (dark green), and dorsal (light green) domains, which correspond to eventual dorsal-intermediate-ventral cartilage identities. Arrows indicate inductive influences by each signal on target genes. The yellow arrow indicates an unknown ventralizing signal X from the endoderm induced in response to Wnt. (B) Diagrams illustrating regulation of Bmp receptor expression along the D-V axis at 24 hpf (colored diagonal bars) by Wnt, Bmp and Edn1.
Mentions: We show that Wnt signaling promotes proliferation and provides ventral-intermediate patterning cues to NC cells in the pharyngeal arches by participating in a regulatory network with Edn1 and Bmp (Fig. 9). By overexpressing Dkk1 or dnTcf3 to disrupt Wnt signaling, we show that Wnt promotes expression of ventral (hand2) and ventral-intermediate genes (dlx3b, dlx5a, msxe) and their corresponding skeletal derivatives, and acts upstream or in parallel to the ventralizing activities of Edn1 and Bmp. Unlike Edn1 and Bmp, however, our chimeric analyses suggest that direct responses to Wnt signaling occur in the pharyngeal endoderm, which also expresses dkk1. This endoderm must secondarily produce as yet unknown signals important for D-V patterning, which regulate the competence of NC cells to respond to Bmp signaling, in part by transcriptionally regulating Bmp receptors. Overexpression of dkk1 also causes a unique midline clefting of the mandible, which we suggest reflects a role in formation of the mouth.

Bottom Line: These D-V patterning defects resemble the phenotypes of zebrafish embryos lacking Bmp or Edn1 signaling, and overexpression of dntcf3 dramatically reduces expression of a subset of Bmp receptors in the arches.Addition of ectopic BMP (or EDN1) protein partially rescues ventral development and expression of dlx3b, dlx5a, and msxe in Wnt signaling-deficient embryos, but surprisingly does not rescue hand2 expression.Similarly, heat-shocked dkk1+ embryos exhibit ventral arch reductions, but also have mandibular clefts at the ventral midline not seen in dntcf3+ embryos.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America.

ABSTRACT
Craniofacial development requires signals from epithelia to pattern skeletogenic neural crest (NC) cells, such as the subdivision of each pharyngeal arch into distinct dorsal (D) and ventral (V) elements. Wnt signaling has been implicated in many aspects of NC and craniofacial development, but its roles in D-V arch patterning remain unclear. To address this we blocked Wnt signaling in zebrafish embryos in a temporally-controlled manner, using transgenics to overexpress a dominant negative Tcf3, (dntcf3), (Tg(hsp70I:tcf3-GFP), or the canonical Wnt inhibitor dickkopf1 (dkk1), (Tg(hsp70i:dkk1-GFP) after NC migration. In dntcf3 transgenics, NC cells in the ventral arches of heat-shocked embryos show reduced proliferation, expression of ventral patterning genes (hand2, dlx3b, dlx5a, msxe), and ventral cartilage differentiation (e.g. lower jaws). These D-V patterning defects resemble the phenotypes of zebrafish embryos lacking Bmp or Edn1 signaling, and overexpression of dntcf3 dramatically reduces expression of a subset of Bmp receptors in the arches. Addition of ectopic BMP (or EDN1) protein partially rescues ventral development and expression of dlx3b, dlx5a, and msxe in Wnt signaling-deficient embryos, but surprisingly does not rescue hand2 expression. Thus Wnt signaling provides ventralizing patterning cues to arch NC cells, in part through regulation of Bmp and Edn1 signaling, but independently regulates hand2. Similarly, heat-shocked dkk1+ embryos exhibit ventral arch reductions, but also have mandibular clefts at the ventral midline not seen in dntcf3+ embryos. Dkk1 is expressed in pharyngeal endoderm, and cell transplantation experiments reveal that dntcf3 must be overexpressed in pharyngeal endoderm to disrupt D-V arch patterning, suggesting that distinct endodermal roles for Wnts and Wnt antagonists pattern the developing skeleton.

Show MeSH
Related in: MedlinePlus