Sprouty was originally identified as an inhibitor of Drosophila epidermal growth factor (EGF) and fibroblast growth factor (FGF) receptor signaling during tracheal development. Four isoforms of mammalian sprouty are known (Spry1-Spry4). The role of the mammalian analogs has not been clearly elucidated although it is believed that human Sprouty 2 (hSpry2) may be an inhibitor of cellular migration and proliferation. Spry2 and Spry4 show considerable sequence homology between human and mouse at the C terminus of the protein. Significant sequence divergence occurs at the N terminus. Spry2 appears to be abundant in brain, lung and heart tissue, with lesser amounts found in kidney and skeletal muscle.