We used our transgenic medaka model (tg(mitf:xmrk)) for melanoma where the pigment cell-transforming oncogene xmrk [24] isolated from the platyfish Xiphophorus maculatus was placed under control of the medaka mitf (microphthalmia-associated transcription factor) promoter, which drives oncogene expression in melanocytes [17]. The gene discussed is TG; the disease is melanoma.