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The ciliary protein Ftm is required for ventricular wall and septal development.

Gerhardt C, Lier JM, Kuschel S, Rüther U - PLoS ONE (2013)

Bottom Line: Despite several studies of the molecular mechanisms involved in ventricular septum (VS) development, very little is known about VS-forming signaling.Since Ftm is a ciliary protein, we investigated presence and function of cilia in murine hearts.Primary cilia could be detected at distinct positions in atria and ventricles at embryonic days (E) 10.5-12.5.

View Article: PubMed Central - PubMed

Affiliation: Institute for Animal Developmental and Molecular Biology, Heinrich Heine University, Düsseldorf, Germany.

ABSTRACT
Ventricular septal defects (VSDs) are the most common congenital heart defects in humans. Despite several studies of the molecular mechanisms involved in ventricular septum (VS) development, very little is known about VS-forming signaling. We observed perimembranous and muscular VSDs in Fantom (Ftm)-negative mice. Since Ftm is a ciliary protein, we investigated presence and function of cilia in murine hearts. Primary cilia could be detected at distinct positions in atria and ventricles at embryonic days (E) 10.5-12.5. The loss of Ftm leads to shortened cilia and a reduced proliferation in distinct atrial and ventricular ciliary regions at E11.5. Consequently, wall thickness is diminished in these areas. We suggest that ventricular proliferation is regulated by cilia-mediated Sonic hedgehog (Shh) and platelet-derived growth factor receptor α (Pdgfrα) signaling. Accordingly, we propose that primary cilia govern the cardiac proliferation which is essential for proper atrial and ventricular wall development and hence for the fully outgrowth of the VS. Thus, our study suggests ciliopathy as a cause of VSDs.

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Shh signaling acts upstream of Pdgfrα signals in cardiac cilia.(A–D) Immunofluorescence on transverse heart sections at E11.5. Cilia are stained in green by acetylated α-tubulin and cell nuclei in blue by DAPI. Scale bars (in white) represent a length of 2 µm. (A) Gli3-190 (red staining) still shows a ciliary localisation in ventricular Ftm−/− cilia. (B) Pdgfrα (red staining) is absent in cilia of Ftm-deficient ventricles. (C) Gli3-190 protein is not observed at cilia of Shh−/− ventricles. (D) Pdgfrα cannot be detected in cilia of Shh-negative ventricles.
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pone-0057545-g007: Shh signaling acts upstream of Pdgfrα signals in cardiac cilia.(A–D) Immunofluorescence on transverse heart sections at E11.5. Cilia are stained in green by acetylated α-tubulin and cell nuclei in blue by DAPI. Scale bars (in white) represent a length of 2 µm. (A) Gli3-190 (red staining) still shows a ciliary localisation in ventricular Ftm−/− cilia. (B) Pdgfrα (red staining) is absent in cilia of Ftm-deficient ventricles. (C) Gli3-190 protein is not observed at cilia of Shh−/− ventricles. (D) Pdgfrα cannot be detected in cilia of Shh-negative ventricles.

Mentions: To elucidate if these signaling pathways are mediated by cardiac cilia, we performed immunofluorescence stainings of proteins which are essential for Shh and Pdgfrα signaling, respectively. The Shh signaling mediator Gli3-190 [41] can be clearly observed at the base of ventricular cilia (Figure 6A, Figure S7A, B) and Pdgfrα is present all along ventricular cilia (Figure 6B). We could neither detect Gli3-190 nor Pdgfrα at E11.5 atrial cilia (data not shown). This indicates that both signaling pathways are mediated by cilia in ventricles but not in atria at E11.5. Since we already detected a downregulation of Shh and Pdgfrα signaling in Ftm-deficient hearts via qRT-PCR, we looked for Gli3-190 and Pdgfrα localisation in Ftm-negative cardiac cilia. In these cilia, Gli3-190 is still present (Figure 7A), while Pdgfrα gets lost in ventricular cilia (Figure 7B). These results let assume that Pdgfrα signaling acts downstream of Shh signaling. To confirm this hypothesis, we investigated Gli3-190 and Pdgfrα localisation at Shh-deficient cilia in the heart. Gli3-190 and Pdgfrα are absent in ventricular cilia (Figure 7C, D) resulting in the conclusion that Pdgfrα signaling functions downstream of Shh signaling in ventricular cilia. The dependency of ventricular Pdgfrα signaling on Shh signaling is confirmed by a smaller amount of the Pdgfrα signaling component pMek1/2 in Shh−/− ventricles (Figure S8). This is indicative of a downregulation of Pdgfrα signaling in Shh-negative ventricles.


The ciliary protein Ftm is required for ventricular wall and septal development.

Gerhardt C, Lier JM, Kuschel S, Rüther U - PLoS ONE (2013)

Shh signaling acts upstream of Pdgfrα signals in cardiac cilia.(A–D) Immunofluorescence on transverse heart sections at E11.5. Cilia are stained in green by acetylated α-tubulin and cell nuclei in blue by DAPI. Scale bars (in white) represent a length of 2 µm. (A) Gli3-190 (red staining) still shows a ciliary localisation in ventricular Ftm−/− cilia. (B) Pdgfrα (red staining) is absent in cilia of Ftm-deficient ventricles. (C) Gli3-190 protein is not observed at cilia of Shh−/− ventricles. (D) Pdgfrα cannot be detected in cilia of Shh-negative ventricles.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585374&req=5

pone-0057545-g007: Shh signaling acts upstream of Pdgfrα signals in cardiac cilia.(A–D) Immunofluorescence on transverse heart sections at E11.5. Cilia are stained in green by acetylated α-tubulin and cell nuclei in blue by DAPI. Scale bars (in white) represent a length of 2 µm. (A) Gli3-190 (red staining) still shows a ciliary localisation in ventricular Ftm−/− cilia. (B) Pdgfrα (red staining) is absent in cilia of Ftm-deficient ventricles. (C) Gli3-190 protein is not observed at cilia of Shh−/− ventricles. (D) Pdgfrα cannot be detected in cilia of Shh-negative ventricles.
Mentions: To elucidate if these signaling pathways are mediated by cardiac cilia, we performed immunofluorescence stainings of proteins which are essential for Shh and Pdgfrα signaling, respectively. The Shh signaling mediator Gli3-190 [41] can be clearly observed at the base of ventricular cilia (Figure 6A, Figure S7A, B) and Pdgfrα is present all along ventricular cilia (Figure 6B). We could neither detect Gli3-190 nor Pdgfrα at E11.5 atrial cilia (data not shown). This indicates that both signaling pathways are mediated by cilia in ventricles but not in atria at E11.5. Since we already detected a downregulation of Shh and Pdgfrα signaling in Ftm-deficient hearts via qRT-PCR, we looked for Gli3-190 and Pdgfrα localisation in Ftm-negative cardiac cilia. In these cilia, Gli3-190 is still present (Figure 7A), while Pdgfrα gets lost in ventricular cilia (Figure 7B). These results let assume that Pdgfrα signaling acts downstream of Shh signaling. To confirm this hypothesis, we investigated Gli3-190 and Pdgfrα localisation at Shh-deficient cilia in the heart. Gli3-190 and Pdgfrα are absent in ventricular cilia (Figure 7C, D) resulting in the conclusion that Pdgfrα signaling functions downstream of Shh signaling in ventricular cilia. The dependency of ventricular Pdgfrα signaling on Shh signaling is confirmed by a smaller amount of the Pdgfrα signaling component pMek1/2 in Shh−/− ventricles (Figure S8). This is indicative of a downregulation of Pdgfrα signaling in Shh-negative ventricles.

Bottom Line: Despite several studies of the molecular mechanisms involved in ventricular septum (VS) development, very little is known about VS-forming signaling.Since Ftm is a ciliary protein, we investigated presence and function of cilia in murine hearts.Primary cilia could be detected at distinct positions in atria and ventricles at embryonic days (E) 10.5-12.5.

View Article: PubMed Central - PubMed

Affiliation: Institute for Animal Developmental and Molecular Biology, Heinrich Heine University, Düsseldorf, Germany.

ABSTRACT
Ventricular septal defects (VSDs) are the most common congenital heart defects in humans. Despite several studies of the molecular mechanisms involved in ventricular septum (VS) development, very little is known about VS-forming signaling. We observed perimembranous and muscular VSDs in Fantom (Ftm)-negative mice. Since Ftm is a ciliary protein, we investigated presence and function of cilia in murine hearts. Primary cilia could be detected at distinct positions in atria and ventricles at embryonic days (E) 10.5-12.5. The loss of Ftm leads to shortened cilia and a reduced proliferation in distinct atrial and ventricular ciliary regions at E11.5. Consequently, wall thickness is diminished in these areas. We suggest that ventricular proliferation is regulated by cilia-mediated Sonic hedgehog (Shh) and platelet-derived growth factor receptor α (Pdgfrα) signaling. Accordingly, we propose that primary cilia govern the cardiac proliferation which is essential for proper atrial and ventricular wall development and hence for the fully outgrowth of the VS. Thus, our study suggests ciliopathy as a cause of VSDs.

Show MeSH
Related in: MedlinePlus