Fibroblast growth factor 4 (FGF-4) is a member of the FGF superfamily (Beenken and Mohammadi). FGF-4 is expressed in pluripotent stem cells and is implicated in various stages of development and morphogenesis in a variety of organisms (Kosaka et al. 2009). FGF-4 has been shown to have an ability to promote neural stem cell proliferation and neuronal differentiation in the postnatal brain (Kosaka et al. 2006). FGF-4 has also been shown to increase the proliferation rate of mesenchymal stem cells (Farré et al.). FGF-4 supports the maintenance and self-renewal properties of human embryonic stem cells and also promotes the proliferation of these cells (Mayshar et al.). In the mouse, the Fgf4 gene also supports proliferation of the inner cell mass (ICM) and postimplantation embryos (Feldman et al.).