Molecular and cellular regulation of renal phosphate transporters in X-linked hypophosphatemia

Recent investigations of X-linked hypophosphatemia support the concept that the kidney is intrinsically normal in this disorder, and that the characteristic phosphaturia is caused by a humoral factor. The mechanisms involved in the pathophysiology of X-linked hypophosphatemia, Hyp, and oncogenic hypophosphatemic osteomalacia are complex and are the results of mutations in a putative zinc metalloprotease. Inactivation inPHEX gene function initiates a series of events that result in severe perturbations in renal Pi transport and metabolism of vitamin D. There are a number of possible working models that could explain the experimental observations. However, our studies clearly show that a humoral factor (phosphatonin) inhibits the transcription of the type II Na+/Pi cotransporter gene (Fig. 4). Phosphatonin may be a key modulator of phosphate homeostasis.