Conotruncal malformations are severe congenital cardiac defects that require surgery early in childhood. Infants born with these defects suffer from significant morbidity and mortality. Abnormal embryonic development of the outflow tract (a region defined as the outflow vessels including the junction with the myocardium, called the arterial pole) produces these defects. In recent studies of the neural crest-ablation model in chick embryos, we have discovered a secondary heart field (SHF) in the ventral pharyngeal mesenchyme that provides myocardial and smooth muscle cells to the arterial pole of the developing heart. After neural crest ablation, myocardium from the SHF is not added to the growing arterial pole and this results in conotruncal malalignment defects such as overriding aorta and double outlet right ventricle. Our preliminary results indicate that the failure of myocardial addition to the outflow tract and subsequent malalignment defects are due to elevated FGF signaling in the caudal pharynx after neural crest ablation based on four pieces of evidence from investigations performed in this laboratory: 1) FGF target genes are elevated after neural crest ablation;2) Fgf8b, the most active isoform of FGF8 is elevated;3) a reporter cell line for FGF registers elevated FGF8b signaling in the ventral pharynx;and 4) blocking FGF8 signaling restores addition of the myocardium from the SHF and normal alignment of the outflow tract in neural crest- ablated embryos. These preliminary data support our overall hypothesis that normal development of the arterial pole depends on the regulation of FGF8b signaling in the pharynx by cardiac neural crest cells. We will test the specific hypotheses: that elevated FGF8b leads to abnormal arterial pole development by affecting proliferation, migration and/or differentiation of the myocardial component of the secondary heart field (aim 1);neural crest cells normally depress FGF8 signaling in the caudal pharynx by endocytosis of the FGF protein and/or by decreasing the transcription of the Fgf8b isoform (aim 2).
In aim 1, we will expose explanted SHF to various concentrations of FGF8b and determine its effect on phospho-ERK, proliferation, migration, cell death and differentiation. We will electroporate an FGF8b expressing plasmid into the pharyngeal endoderm of chick embryos in ovo to correlate developmental events in the secondary heart field with outflow alignment.
In aim 2, we will determine the dynamics of FGF8b endocytosis in vitro followed by blocking endocytosis in vivo to determine its role in outflow alignment. Finally we will determine the relationship of neural crest with endoderm and ectoderm in controling FGF8b isoform expression. Together these studies will advance the mechanistic understanding of neural crest function in heart development and will provide insight into factors that cause conotruncal malformations.
| Sato, Asako; Scholl, Ann Marie; Kuhn, E B et al. (2011) FGF8 signaling is chemotactic for cardiac neural crest cells. Dev Biol 354:18-30 |
| Kirby, Margaret L; Sahn, David J (2010) Mouse models of congenital heart defects: what's missing? Circ Cardiovasc Imaging 3:228-30 |
| Evans, Sylvia M; Yelon, Deborah; Conlon, Frank L et al. (2010) Myocardial lineage development. Circ Res 107:1428-44 |
| Kirby, Margaret L; Hutson, Mary R (2010) Factors controlling cardiac neural crest cell migration. Cell Adh Migr 4:609-21 |
| Hutson, Mary Redmond; Zeng, Xiaopei Lily; Kim, Andrew J et al. (2010) Arterial pole progenitors interpret opposing FGF/BMP signals to proliferate or differentiate. Development 137:3001-11 |
| Dyer, Laura A; Makadia, Frini A; Scott, Alexandria et al. (2010) BMP signaling modulates hedgehog-induced secondary heart field proliferation. Dev Biol 348:167-76 |
| Scholl, Ann Marie; Kirby, Margaret L (2009) Signals controlling neural crest contributions to the heart. Wiley Interdiscip Rev Syst Biol Med 1:220-7 |
| van den Berg, Gert; Abu-Issa, Radwan; de Boer, Bouke A et al. (2009) A caudal proliferating growth center contributes to both poles of the forming heart tube. Circ Res 104:179-88 |
| Dyer, Laura A; Kirby, Margaret L (2009) Sonic hedgehog maintains proliferation in secondary heart field progenitors and is required for normal arterial pole formation. Dev Biol 330:305-17 |
| Kirby, Margaret L (2009) Why don't they beat?: Cripto, apelin/APJ, and myocardial differentiation. Circ Res 105:211-3 |
Showing the most recent 10 out of 17 publications
