SLC13A4 encodes a sodium-sulfate symporter (NaS2) that mediates high-affinity sulfate transport with electrogenic properties 1. The protein functions as a plasma membrane transporter with a 3:1 Na+:SO4²⁻ stoichiometry and a Km of 0.38mM for sulfate, indicating high substrate affinity 21. SLC13A4 is abundantly expressed in placenta, where it localizes to syncytiotrophoblasts and plays a crucial role in transporting maternal sulfate to the developing fetus 34. The transporter also shows expression in brain, testis, heart, thymus, and liver 2. SLC13A4 is inhibited by thiosulfate, phosphate, molybdate, selenate and tungstate, but not by organic anions or DIDS 2. The gene contains 16 exons spanning approximately 47-70kb and produces alternatively spliced variants, with variant 1 being 4-fold more abundant than variant 2 in placental tissues 24. Genetic variants including missense mutations and frameshift variants can cause partial or complete loss of function, with some affecting subcellular localization 4. Given sulfate's essential role in fetal development and the fetus's complete dependence on maternal sulfate supply, SLC13A4 dysfunction may contribute to developmental abnormalities, though clinical significance in humans requires further investigation 4.