Transmembrane protein 216, TMEM216 of 160 aas and 4 TMSs. TMEM216 deletion causes mislocalization of cone opsin and rhodopsin with photoreceptor degeneration in Zebrafish (Liu et al. 2020). Mutations in TMEM216, a ciliary transition zone tetraspan transmembrane protein, are linked to Joubert syndrome and Meckel syndrome, and photoreceptor degeneration is a prominent phenotype in Joubert syndrome. Homozygous tmem216 knockout zebrafish died before 21 days after fertilization. Their retina exhibited reduced immunoreactivity to rod photoreceptor outer segment marker 4D2 and cone photoreceptor outer segment marker G protein subunit alpha-transducin 2 (GNAT2). Thus, TMEM216 is essential for normal genesis of outer segment disc structures, transport of outer segment materials, and survival of photoreceptors in zebrafish (Liu et al. 2020)).