KIT is a proto-oncogene encoding a transmembrane tyrosine kinase receptor for stem cell factor required for normal hematopoiesis, melangenesis and gametogenesis. Mutations in KIT are associated with gastrointestinal stromal tumors, mast cell disease, acute myelogenous leukemia, and piebaldism. The clinically observed V654A mutant has been demonstrated to be resistant to inhibition with imatinib.