In 2002, the research group of Dr. Schinkel first provided evidence that ABCG2-knockout mice are extremely sensitive to the dietary chlorophyll-breakdown product pheophorbide a, which suggests that ABCG2 expressed in the small intestine plays a critical role in reducing the risk for developing diet-dependent phototoxicity and protoporphyria [46]. The gene discussed is ABCG2; the disease is erythropoietic protoporphyria.