The human gene SLC5A2 encodes a sodium-dependent glucose transporter, SGLT2 (Wells et al. 1992). SLC5A2 is expressed in many tissues but primarily in the kidney, specifically the renal proximal tubules (S1 and S2 segments). It is a low affinity, high capacity transporter of glucose across the apical membrane, with co-transport of Na+ ions in a 1:1 ratio. Unlike SGLT1, it doesn't transport galactose. SLC5A2 is the main transporter of glucose in the kidney, responsible for approximately 98% of glucose reabsorption (remainder by SGLT1). Defects in SLC5A2 are the cause of renal glucosuria (GLYS1), an autosomal recessive renal tubular disorder (Calado et al. 2004). A separate sodium dependent glucose transporter NAGLT1, was identified in the multifacilitator superfamily (MFS) and could be a transporter of glucose in kidney proximal tubules. Its rat orthologue, Naglt1, has been shown to mediate tubular reabsorption of glucose (Horiba et al. 2003). By similarity, SLC5A1, 4 and 9 are predicted proteins that transport glucose in a Na+-dependent manner.