The Eyes absent homolog1 (EYA1) is expressed in metanephric mesenchyme and specifies metanephric mesenchyme, which interacts with the nephric duct to regulate formation of the ureteric bud (inferred from mouse homologs). Odd skipped related 1 (OSR1, also called ODD1) activates expression of EYA1 in the metanephric mesenchyme (inferred from mouse homologs). Mice lacking Eya1 fail to form kidneys (Xu et al. 1999). Mice that lack Osr1 do not express detectable Eya1, indicating an absolute requirement for Osr1 (James et al. 2006). The Osr1 mutants also have abnormalities of the nephric duct and mesonephros and they fail to form metanephric mesenchyme (James et al. 2006).