Transmembrane Protein 231 (TMEM231) is a transmembrane component of the tectonic-like complex, a complex localized at the transition zone of primary cilia and acting as a barrier that prevents diffusion of transmembrane proteins between the cilia and plasma membranes. TMEM231is required for ciliogenesis and sonic hedgehog/SHH signaling (By similarity). TMEM231 is involved in the formation of the diffusion barrier between the cilia and plasma membrane. Mutations in TMEM231 gene cause Joubert syndrome (JBTS). Multiple alternatively spliced transcript variants have been found for this gene.