KL and chronic kidney disease: As we recently showed,29 B6 Col4a3−/− mice with advanced CKD expectedly showed reduced renal Klotho expression and significant alterations of mineral metabolism, including elevated serum cFGF23, iFGF23, PTH, phosphate, and calcium levels, normal 1,25(OH)2D levels, and increased phosphate and calcium excretion compared to B6 WT mice (Fig. 4a–j).