Paracellin-1

Paracellin-1, also known as Claudin 16, is one of the transmembrane linker proteins of tight junctions and is part of the Claudin family.  This protein is only found in the thick ascending limb of the Loop of Henle in the Renal Tubule. 

Mutation of Paracellin-1

Recessive mutations in Paracellin-1 leads to hypomagnesaemia in humans.  Magnesium movement in the thick ascending limb is controlled by a paracellular pathway which is altered by mutations in Paracellin-1 which therefore leads to less magnesium being reabsorbed.  Calcium movement is also disturbed causing hypocalcaemia.