The klotho (Kl–/–) and/or Fgf23 (Fgf23–/–) knockout mice exhibit many key aspects associated with human CAVD including, premature aging, kidney disease, increased serum phosphate levels (i.e., hyperphosphatemia), and increased osteogenic gene expression (7, 23, 24). The gene discussed is KL; the disease is congenital bilateral aplasia of vas deferens from CFTR mutation.