PAX9 is a member of the paired box (PAX) family of transcription factors. Proteins in this family typically contain a paired box domain, a paired type homeodomain and an octapeptide sequence. They are important during fetal development and have also been implicated in cancer growth.The exact role of PAX9 is unclear, but it is thought to be involved in development of various organs, skeletal tissue and stratified squamous epithelia. Mutations in PAX9 have also been implicated in oligodontia, a type of tooth agenesis which is a common developmental anomoly in humans.