For example, the Asp816Phe and Asp816Val mutations (the aspartate normally at position 816 in the c-kit protein has been replaced with phenylalanine or valine respectively) have been associated with early manifestation of the disease (mean age of onset: 1.3 and 5.9 months respectively).[3][4] The c-kit gene is encoded on the q12 locus of chromosome 4.[5]