SLC12A2 encodes the Na-K-2Cl cotransporter-1 (NKCC1), a cation-chloride cotransporter mediating electroneutral transport of chloride, potassium, and sodium ions across cell membranes 1. It plays a vital role in regulating ionic balance and cell volume 1. NKCC1 is particularly important in the thick ascending limb of the renal loop of Henle, where mutations cause Bartter syndrome characterized by renal salt wasting, hypokalemic metabolic alkalosis, and hypercalciuria 2. Loss-of-function SLC12A2 mutations are associated with neurodevelopmental deficits, deafness (autosomal dominant deafness 78), and variable fluid secretion abnormalities across epithelia 3. The gene appears to be haploinsufficient, with single allelic deleterious variants causing disease in some patients 3. Beyond inherited disorders, SLC12A2 dysfunction has broader clinical relevance: ammonium uptake through SLC12A2 promotes drug resistance in multiple myeloma by stabilizing NEK2 protein 4, and altered SLC12A2 expression is associated with increased breast cancer risk 5. Dysregulated SLC12A2 has also been implicated in osteoporosis pathogenesis 6. Current therapeutic approaches include loop diuretics like furosemide that downregulate SLC12A2 expression to mitigate pathological effects 4.