HF-related activation of NPPA/NPPB gene expression has been demonstrated to be driven partly through mitogen-activated protein kinases (MAPKs), specifically mediated via extracellular signal-related kinase- (ERK-) signaling (Bueno et al., 2000; Kehat et al., 2011; Koivisto et al., 2011), with GATA4(Liang et al., 2001; Kerkela et al., 2002; Tenhunen et al., 2004; van Berlo et al., 2011), NFAT (Molkentin et al., 1998), Myocardin (Kuwahara et al., 2010) being some examples of key transcription factors involved. Here, NPPB is linked to hydrops fetalis.