SLC4A4 (Solute Carrier Family 4 Member 4) is a gene that encodes a sodium bicarbonate cotransporter involved in regulating acid-base balance in the body. Mainly expressed in the kidneys and pancreas, it plays a key role in bicarbonate reabsorption and pH regulation. Disruptions in SLC4A4 function can impair the body's ability to maintain acid-base homeostasis, contributing to conditions such as renal tubular acidosis.