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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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Ftm-negative hearts display a disturbance in Gli3 processing.(A) Western blot analysis of E11.5 embryo and heart protein lysates. Actin serves as loading control. In Ftm-negative embryos (n = 3), there is more Gli3-190 protein than in wild-type littermates, but an equal amount of Gli3-83. The amount of Gli3-190 protein is higher in Ftm-deficient than in wild-type hearts (n = 12, respectively), while conversely, there is less Gli3-83 in Ftm−/− hearts indicating a processing defect in Ftm-negative hearts. (B, C) Graphical evaluation of the Gli3-190/Gli3-83 ratio in wild-type and Ftm-deficient embryos and hearts, respectively. (B) The ratio of Gli3-190/Gli3-83 is 2.64 fold elevated in Ftm-homozygous mutant embryos. (C) Gli3-190/Gli3-83 ratio is 10.94 fold increased in Ftm-negative hearts.
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pone-0057545-g008: Ftm-negative hearts display a disturbance in Gli3 processing.(A) Western blot analysis of E11.5 embryo and heart protein lysates. Actin serves as loading control. In Ftm-negative embryos (n = 3), there is more Gli3-190 protein than in wild-type littermates, but an equal amount of Gli3-83. The amount of Gli3-190 protein is higher in Ftm-deficient than in wild-type hearts (n = 12, respectively), while conversely, there is less Gli3-83 in Ftm−/− hearts indicating a processing defect in Ftm-negative hearts. (B, C) Graphical evaluation of the Gli3-190/Gli3-83 ratio in wild-type and Ftm-deficient embryos and hearts, respectively. (B) The ratio of Gli3-190/Gli3-83 is 2.64 fold elevated in Ftm-homozygous mutant embryos. (C) Gli3-190/Gli3-83 ratio is 10.94 fold increased in Ftm-negative hearts.

Mentions: Since the phenotype of Shh-deficient hearts, which display atrioventricular septal defects, appears to be much stronger than in Ftm-negative embryos [61], Ftm functions most likely downstream of Shh ligand in this pathway. The phenotypes of mice, which are negative for Ptc1 and Smo, two components of the Shh pathway downstream of its ligand, are also more severe than the Ftm-deficient phenotype [57], [62], so that we focused on the next players within this signaling cascade − the Gli proteins. We examined Gli3 processing by western blot analysis, using an antibody against the N-terminus of Gli3 that detects both the full-length (Gli3-190) and processed short, repressor (Gli3-83) forms. Previously, we were able to show that the ratio of Gli3-190/Gli3-83 is higher in Ftm−/− whole embryo protein lysates than in wild-type or Ftm-heterozygous ones (Figure 8A, B) [20]. In Ftm-deficient hearts, we also detected an increase of the Gli3-190/Gli-83 ratio at E11.5 (Figure 8A,C) confirming our assumption of a Gli3 processing defect. The ratio of Gli3-190/Gli3-83 in Ftm-negative embryos is 2.64 fold higher than in the wild-type (Figure 8B), while in Ftm-deficient hearts, the Gli3-190/Gli3-83 ratio is 10.94 fold higher than in their wild-type counterparts (Figure 8C).


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

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

Ftm-negative hearts display a disturbance in Gli3 processing.(A) Western blot analysis of E11.5 embryo and heart protein lysates. Actin serves as loading control. In Ftm-negative embryos (n = 3), there is more Gli3-190 protein than in wild-type littermates, but an equal amount of Gli3-83. The amount of Gli3-190 protein is higher in Ftm-deficient than in wild-type hearts (n = 12, respectively), while conversely, there is less Gli3-83 in Ftm−/− hearts indicating a processing defect in Ftm-negative hearts. (B, C) Graphical evaluation of the Gli3-190/Gli3-83 ratio in wild-type and Ftm-deficient embryos and hearts, respectively. (B) The ratio of Gli3-190/Gli3-83 is 2.64 fold elevated in Ftm-homozygous mutant embryos. (C) Gli3-190/Gli3-83 ratio is 10.94 fold increased in Ftm-negative hearts.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585374&req=5

pone-0057545-g008: Ftm-negative hearts display a disturbance in Gli3 processing.(A) Western blot analysis of E11.5 embryo and heart protein lysates. Actin serves as loading control. In Ftm-negative embryos (n = 3), there is more Gli3-190 protein than in wild-type littermates, but an equal amount of Gli3-83. The amount of Gli3-190 protein is higher in Ftm-deficient than in wild-type hearts (n = 12, respectively), while conversely, there is less Gli3-83 in Ftm−/− hearts indicating a processing defect in Ftm-negative hearts. (B, C) Graphical evaluation of the Gli3-190/Gli3-83 ratio in wild-type and Ftm-deficient embryos and hearts, respectively. (B) The ratio of Gli3-190/Gli3-83 is 2.64 fold elevated in Ftm-homozygous mutant embryos. (C) Gli3-190/Gli3-83 ratio is 10.94 fold increased in Ftm-negative hearts.
Mentions: Since the phenotype of Shh-deficient hearts, which display atrioventricular septal defects, appears to be much stronger than in Ftm-negative embryos [61], Ftm functions most likely downstream of Shh ligand in this pathway. The phenotypes of mice, which are negative for Ptc1 and Smo, two components of the Shh pathway downstream of its ligand, are also more severe than the Ftm-deficient phenotype [57], [62], so that we focused on the next players within this signaling cascade − the Gli proteins. We examined Gli3 processing by western blot analysis, using an antibody against the N-terminus of Gli3 that detects both the full-length (Gli3-190) and processed short, repressor (Gli3-83) forms. Previously, we were able to show that the ratio of Gli3-190/Gli3-83 is higher in Ftm−/− whole embryo protein lysates than in wild-type or Ftm-heterozygous ones (Figure 8A, B) [20]. In Ftm-deficient hearts, we also detected an increase of the Gli3-190/Gli-83 ratio at E11.5 (Figure 8A,C) confirming our assumption of a Gli3 processing defect. The ratio of Gli3-190/Gli3-83 in Ftm-negative embryos is 2.64 fold higher than in the wild-type (Figure 8B), while in Ftm-deficient hearts, the Gli3-190/Gli3-83 ratio is 10.94 fold higher than in their wild-type counterparts (Figure 8C).

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