MAGED2 is an X-linked gene encoding melanoma-associated antigen D2 (MAGE-D2), a protein essential for renal salt homeostasis and fetal development. Primary function: MAGED2 regulates the expression, localization, and function of sodium chloride cotransporters NKCC2 and NCC in the distal renal tubule, which are critical for renal salt reabsorption 1. Mechanism: MAGED2 operates through adenylate cyclase and cyclic AMP (cAMP) signaling pathways 1, with PKA type II as a key downstream effector 2. Under hypoxic conditions, MAGED2 prevents excessive endocytosis of GΞ±s, maintaining AC activation and cAMP production necessary for NCC trafficking and membrane localization 3. Disease relevance: MAGED2 mutations cause X-linked transient antenatal Bartter syndrome (aBS), characterized by severe polyhydramnios, prematurity, and perinatal salt-wasting 14. Affected male infants show high perinatal mortality (32%) and clinical anomalies in 76% of cases, though surviving infants experience spontaneous symptom resolution 4. Clinical significance: Antenatal diagnosis via whole-exome sequencing enables intervention through serial amnioreductions, which significantly improve outcomes with lower gestational ages at delivery (30.71 vs 28.7 weeks) and eliminate neonatal mortality 5. Additionally, MAGED2 functions as a host antiviral factor, restricting SARS-CoV-2 replication by disrupting nucleocapsid-genome interactions until cleaved by viral protease 6.