TSPAN8 (tetraspanin 8), also known as TM4SF3 or CO-029, is a 237 amino acid multi-pass membrane protein that belongs to the tetraspanin family of transmembrane proteins and is thought to play a role in signal transduction events that influence cell development, activation, growth and motility. Localized to the cell membrane, TSPAN8 is expressed in colon, gastric, renal and pancreatic cancers, strongly suggesting a role in cancer formation and metastasis. The gene encoding TSPAN8 maps to human chromosome 12, which encodes over 1,100 genes and comprises approximately 4.5% of the human genome. Chromosome 12 is associated with a variety of diseases and afflictions, including hypochondrogenesis, achondrogenesis, Kniest dysplasia, Noonan syndrome and Trisomy 12p, which causes facial developmental defects and seizure disorders.