Expression of the gene Nppb, which encodes the brain natriuretic peptide (BNP) and is upregulated when the ventricles are subjected to increased filling pressures and left ventricle wall stretch22, was increased in the Notch3-/- hearts (Fig. 1E), corroborating the notion of left ventricular hypertrophy. Here, NPPB is linked to left ventricular hypertrophy.