Mediates electroneutral potassium-chloride cotransport when activated by cell swelling (By similarity). May mediate K(+) uptake into Deiters' cells in the cochlea and contribute to K(+) recycling in the inner ear. Important for the survival of cochlear outer and inner hair cells and the maintenance of the organ of Corti. May be required for basolateral Cl(-) extrusion in the kidney and contribute to renal acidification. Inhibited by WNK3. Homomultimer and heteromultimer with other K-Cl cotransporters. Detected in proximal tubules in the kidney, in particular in basolateral membranes of intercalated cells in the cortical collecting duct. In 8 day old mice, before the onset of hearing, detected in membranes of the stria vascularis and in most cells of the organ of Corti. At P14, when the organ of Corti has matured, expression is no longer detected in hair cells and the stria, but is restricted to Deiters' cells that are supporting outer hair cells and to phalangeal cells enveloping the inner hair cells. Glycosylation at Asn-331 and Asn-344 is required for proper trafficking to the cell surface, and augments protein stability. Defects in Slc12a7 are a cause of deafness due to the progressive degeneration of outer and inner hair cells in the cochlea and of neurons in the cochlear ganglion, leading to the loss of the organ of Corti. Belongs to the SLC12A transporter family. Extended N-terminus.