NET-4, also known as TSPAN5 or TM4SF9, is a 268 amino acid multi-pass membrane protein that belongs to the tetraspanin family and is thought to play a role in signal transduction events related to cell development, activation, growth and motility. The gene encoding NET-4 maps to human chromosome 4, which encodes nearly 6% of the human genome and has the largest gene deserts (regions of the genome with no protein encoding genes) of all of the human chromosomes. Defects in some of the genes located on chromosome 4 are associated with Huntington's disease, Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.