How are changes in the KL gene related to health conditions?
hyperphosphatemic familial tumoral calcinosis - caused by mutations in the KL gene
At least one mutation in the KL gene has been found to cause hyperphosphatemic familial tumoral calcinosis (HFTC), a condition characterized by an increase in the levels of phosphate in the blood (hyperphosphatemia) and abnormal deposits of phosphate and calcium (calcinosis) in the body's tissues. The KL gene mutation that causes HFTC replaces the protein building block (amino acid) histidine with the amino acid arginine at position 193 in the protein sequence (written as His193Arg or H193R). This mutation results in a shortage of functional alpha-klotho. As a result, FGF receptor 1 is not activated, making it unavailable for fibroblast growth factor 23 binding. The fibroblast growth factor 23 protein is normal, but it cannot bind to its receptor and cannot send out signals to stop phosphate reabsorption. As a result, too much phosphate is reabsorbed into the bloodstream, leading to hyperphosphatemia and subsequent calcinosis.