The FGF-BMP signaling axis regulates outflow tract valve primordium formation by promoting cushion neural crest cell differentiation.
BACKGROUND
Heart valves develop from precursor structures called cardiac cushions, an endothelial-lined cardiac jelly that resides in the inner side of the heart tube. The cushions are then invaded by cells from different sources, undergo a series of complicated and poorly understood remodeling processes, and give rise to valves. Disruption of the fibroblast growth factor (FGF) signaling axis impairs morphogenesis of the outflow tract (OFT). Yet, whether FGF signaling regulates OFT valve formation is unknown.


OBJECTIVE
To study how OFT valve formation is regulated and how aberrant cell signaling causes valve defects.


RESULTS
By using mouse genetic manipulation, cell lineage tracing, ex vivo heart culture, and molecular biology approaches, we demonstrated that FGF signaling in the OFT myocardium upregulated Bmp4 expression, which then enhanced smooth muscle differentiation of neural crest cells (NCCs) in the cushion. FGF signaling also promoted OFT myocardial cell invasion to the cushion. Disrupting FGF signaling interrupted cushion remodeling with reduced NCCs differentiation into smooth muscle and less cardiomyocyte invasion and resulted in malformed OFT valves.


CONCLUSIONS
The results demonstrate a novel mechanism by which the FGF-BMP signaling axis regulates formation of OFT valve primordia by controlling smooth muscle differentiation of cushion NCCs.
Zhang
Jue
J
Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030-3303, USA.
Chang
Julia Y F
JY
Huang
Yanqing
Y
Lin
Xiang
X
Luo
Yongde
Y
Schwartz
Robert J
RJ
Martin
James F
JF
Wang
Fen
F
D000818:Animals; D001665:Binding Sites; D055415:Bone Morphogenetic Protein 4 / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage; D002478:Cells, Cultured; D004694:Endocardial Cushion Defects / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D054089:Endocardial Cushions / Q000378:metabolism* / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D005838:Genotype; D006321:Heart / Q000196:embryology*; D006351:Heart Valves / Q000002:abnormalities / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D009024:Morphogenesis; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D009432:Neural Crest / Q000002:abnormalities / Q000378:metabolism* / Q000473:pathology; D009924:Organ Culture Techniques; D010641:Phenotype; D011401:Promoter Regions, Genetic; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection
C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; C488187:FRS2alpha protein, mouse; D008565:Membrane Proteins; D018808:Transcription Factor AP-1; D016222:Fibroblast Growth Factor 2; C496349:Fgfr1 protein, mouse; C496354:Fgfr2 protein, mouse; D051496:Receptor, Fibroblast Growth Factor, Type 1; D051497:Receptor, Fibroblast Growth Factor, Type 2