The tetraspanin family is a group of cell surface proteins that regulate cell development, activation, growth and motility. Each member contains four hydrophobic domains and participates in the mediation of signal transduction. NET-5, also known as TSPAN9 (tetraspanin 9), is a 239 amino acid multi-pass membrane protein that belongs to the tetraspanin (TM4SF) family. NET-5 forms a complex with GPVI in the tetraspanin microdomains on the platelet surface, and is encoded by a gene that maps to human chromosome 12p13.33. Chromosome 12 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.