The Nu/Nu phenotype is also likely to offer novel insights in HF morphogenesis and cycling related to interactions between the epithelial and mesenchymal cell lineage with several signaling pathways such as that related to bone morphogenetic proteins (BMP’s) [58], [59], tumor growth factor β (TGF-β) [60] or insulin like growth factor 1 (IGF-1) [61] being worthwhile further investigation. Here, IGF1 is linked to hydrops fetalis.