FGFR1 and chronic kidney disease: In the non-cKO groups, plasma calcium levels significantly decreased in CKD mice compared with non-CKD mice (control): Fgfr1–3flox/flox, control (9.4 ± 0.5 mg/dL, n = 10) vs CKD (8.1 ± 0.8 mg/dL, n = 9), P < 0.001; αKlothoflox/flox, control (9.2 ± 0.3 mg/dL, n = 18) vs CKD (8.3 ± 0.6 mg/dL, n = 11), P < 0.001; Fgfr1–4flox/flox, control(8.9 ± 0.5 mg/dL, n = 11) vs CKD (8.3 ± 0.4 mg/dL, n = 8), P < 0.05.