KCNJ1 and Bartter syndrome: Bartter syndrome could be caused by mutations of NKCC2 (Na+-K+-2Cl− cotransporter) expressed in the thick ascending limb (TAL) of Henle loop (Type 1 Bartter Syndrome) [12], ROMK (outwardly rectifying potassium channel) (Type 2 Bartter Syndrome), or CLCNKB (chloride channel) (Type 3 Bartter Syndrome) which is a regulator of NKCC2.