ABCB1 and erythropoietic protoporphyria: Mice lacking ABCB1 or ABCG2 do not show altered phenotypes [25], [26] except for higher brain concentrations of ABCB1-transported agents/ligands, an increased immunological response to normal bacterial flora (ABCB10/0) [27], and a distinct form of dietary-induced protoporphyria (ABCG20/0) [28]; however, these studies did not investigate neurogenic or cognitive functions.