Tetraspanins are a group of hydrophobic membrane proteins that interact with a wide variety of proteins including intracellular signaling molecules, integrins and membrane receptors. TSPAN7 (tetraspanin 7), also known as MXS1 (membrane component chromosome X surface marker 1) or TM4SF2 (transmembrane 4 superfamily member 2), is a 249 amino acid multi-pass membrane protein belonging to the tetraspanin (TM4SF) family of transmembrane proteins. TSPAN7 is believed to play a role in cell motility and cell proliferation. The gene that encodes TSPAN7 maps to human chromosome X and defects in this gene are a cause of mental retardation X-linked type 58 (MRX58), which is characterized by dramatically below average general intellectual functioning.