PROBLEM TO BE SOLVED: To provide a model animal where pigmentation in human skin is reproduced.SOLUTION: A hairless rodent gene-modified animal, into which an activated RET gene is introduced and which has melanogenesis, is provided. In this gene-modified animal, melanogenesis is accelerated in a basal epidermal layer by the irradiation of ultraviolet rays to the skin, which results in delayed pigmentation via recovery from pigmentation after production of temporary pigmentation. A screening method for matter, which is effective for prevention or treatment of delayed pigmentation, is characterized by using a gene-modified animal.【課題】ヒト皮膚における色素沈着を再現したモデル動物を提供する。【解決手段】活性化型RET遺伝子が遺伝子導入されており且つメラニン産生能を有するヘアレス齧歯類遺伝子改変動物を提供。皮膚への紫外線照射によって、表皮基底層でメラニン産生が亢進して一時的色素沈着が生じた後、該色素沈着からの回復を経て遅延性色素沈着が生ずる、遺伝子改変動物。遺伝子改変動物を用いることを特徴とする、遅延性色素沈着の予防又は治療に有効な物質のスクリーニング方法。【選択図】なし
