Congenital heart disease – the commonest type of human birth defect – is the result of abnormal early heart development. In this issue, two papers investigate how opposing fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) signals control the differentiation of the secondary heart field (SHF) and anterior heart field (AHF) cardiac progenitors during early vertebrate heart development.
On p. 3001, by isolating and culturing chick SHF mesoderm, which forms the myocardium and smooth muscle of the heart's arterial pole (the outflow region of the heart), Mary Hutson and colleagues show that this tissue contains stem cells that can differentiate into myocardium, smooth muscle and endothelial cells. By treating SHF (arterial pole) progenitor cultures with combinations of growth factors and inhibitors, the researchers show that BMP promotes myocardial differentiation but not proliferation of the arterial pole progenitors, whereas FGF promotes their proliferation and smooth muscle cell differentiation but...
