Previously, transgenic mice with hypomorphic Kl alleles (kl/kl mice) and kidney-specific Kl null (Six-2-kl-/-) mice, that had hyperphosphataemia, EC and shortened lifespan have been reported [11, 22] (Table 1), and thus our findings of these ENU-induced mouse mutants represents the first report of EC mouse models with Kl coding sequence mutations, which will help to further elucidate the molecular basis of klotho function and characterise the role of the FGF23-klotho pathway in the renal regulation of phosphate metabolism. Here, FGF23 is linked to hyperphosphatemia.