TMEFF1 is a novel transmembrane protein, containing two follisatin domains and an epidermal growth factor-like region. The ectopic expression of TMEFF1 in brain cancer cells resulted in their growth inhibition. That TMEFF1 may behave as a tumor suppressor gene in brain cancers. TMEFF1 and TMEFF2 are putative transmembrane proteins comprised of one epidermal growth factor (EGF)-like domain and two follistatin-like domains. Both TMEFF1 and TMEFF2 are predominantly expressed in the brain.