The TMEM231 gene encodes a transmembrane ciliary protein that is a component of the tectonic-like complex, also known as the B9 or MKS complex. This complex localizes to the basal body, a ring like structure in the transition zone at the base of the primary cilia, and plays an important role in preventing the diffusion of transmembrane proteins between the cilia and plasma membranes. Knockdown of TMEM231 negatively affects ciliogenesis, probably because the diffusion barrier created by the B9 complex is essential for the formation and retention of ciliary components. The protein is also involved in the Sonic hedgehog signaling pathway. Based on studies of mouse orthologs, human TMEM231 protein is predicted to play a role in in-utero embryonic development, vasculature development, digit morphogenesis, eye development and neuroepithelial cell differentiation.
Mutations in the TMEM231 gene are associated with Meckel Syndrome, type 11 (MKS11) and Joubert Syndrome 20 (JBTS20). MKS11 is an often fatal ciliopathy defined by the presence of occipital encephalocele, polydactyly, and polycystic kidneys. JBTS20 is a phenotypically diverse disorder characterized by hypoplasia of the cerebellar vermis resulting in the neuroradiologic molar tooth sign, along with other neurological, ocular and renal manifestations.