The CT domain is similar to those found in many extracellular matrix proteins, including Drosophila melanogaster slit, the von Willebrand factor, several mucins, Norrie disease protein and a wide variety of small growth factors, including VEGF, TGF-β, BMPs, nerve growth factor (NGF) and platelet-derived growth factor (PDGF) [1,88]. Here, NGF is linked to glycogen storage disease VI.