Murine Jagged1/Notch signaling in the second heart field orchestrates Fgf8 expression and tissue-tissue interactions during outflow tract development
Frances A. High, … , Warren S. Pear, Jonathan A. Epstein
Frances A. High, … , Warren S. Pear, Jonathan A. Epstein
Published June 8, 2009
Citation Information: J Clin Invest. 2009;119(7):1986-1996. https://doi.org/10.1172/JCI38922.
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Murine Jagged1/Notch signaling in the second heart field orchestrates Fgf8 expression and tissue-tissue interactions during outflow tract development

Abstract

Notch signaling is vital for proper cardiovascular development and function in both humans and animal models. Indeed, mutations in either JAGGED or NOTCH cause congenital heart disease in humans and NOTCH mutations are associated with adult valvular disease. Notch typically functions to mediate developmental interactions between adjacent tissues. Here we show that either absence of the Notch ligand Jagged1 or inhibition of Notch signaling in second heart field tissues results in murine aortic arch artery and cardiac anomalies. In mid-gestation, these mutants displayed decreased Fgf8 and Bmp4 expression. Notch inhibition within the second heart field affected the development of neighboring tissues. For example, faulty migration of cardiac neural crest cells and defective endothelial-mesenchymal transition within the outflow tract endocardial cushions were observed. Furthermore, exogenous Fgf8 was sufficient to rescue the defect in endothelial-mesenchymal transition in explant assays of endocardial cushions following Notch inhibition within second heart field derivatives. These data support a model that relates second heart field, neural crest, and endocardial cushion development and suggests that perturbed Notch-Jagged signaling within second heart field progenitors accounts for some forms of congenital and adult cardiac disease.

Authors

Frances A. High, Rajan Jain, Jason Z. Stoller, Nicole B. Antonucci, Min Min Lu, Kathleen M. Loomes, Klaus H. Kaestner, Warren S. Pear, Jonathan A. Epstein

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Figure 4

Notch regulates Fgf8 expression in the second heart field.

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Notch regulates Fgf8 expression in the second heart field. (A and B) Lig...
(A and B) Light microscopy of E9.5 hearts of control (A) and Islet1Cre/+;DNMAML mutants (B). The mutant OFT (arrow) and right ventricle (arrowhead) were hypoplastic. (C and D) H&E-stained sections of E10.5 OFT cushions in control (C) and Islet1Cre/+;DNMAML mutant (D). The mutant OFT cushions (arrowheads) were hypocellular (D). (E and F) Quantitative RT-PCR of DAPT-treated cultured pharyngeal explants (E) or tissue directly isolated from E10.5 embryos (F), expressed relative to controls. (E) The data represent an average of 4 independent experiments, with error bars indicating 1 standard deviation. Asterisks indicate gene products that showed statistically significant changes in all 4 experiments (P < 0.02). (F) Fgf8 expression levels in the anterior pharynx and OFT of E10.5 control and mutant embryos. The data represent the average of 3 pools of 3–4 embryos per genotype. (G–J) In situ hybridizations showing Fgf8 expression in the OFT of E9.5 control (G and I) and mutant embryos (H and J). Arrowheads point to developing OFT myocardium. (K and L) In situ hybridization for Bmp4 at E11.5 in control (K) and mutant (L) embryos. (M and N) Immunohistochemistry for phospho-Smad in the OFT at E10.5 of control (M and O) and mutant (N and P) embryos showed robust phospho-Smad expression in the OFT cushions (circled) and endothelium (arrowheads) of controls with decreased expression in mutants. Control genotype was Islet1+/+;DNMAML. Scale bars: 100 μm (C–H, K–P), 250 μm (A, B, I, and J).