TMEM107 recruits ciliopathy proteins to subdomains of the ciliary transition zone and causes Joubert syndrome.
Lambacher NJ, Bruel AL, van Dam TJ, Szymańska K, Slaats GG, Kuhns S, McManus GJ, Kennedy JE, Gaff K, Wu KM, van der Lee R, Burglen L, Doummar D, Rivière JB, Faivre L, Attié-Bitach T, Saunier S, Curd A, Peckham M, Giles RH, Johnson CA, Huynen MA, Thauvin-Robinet C, Blacque OE.
Nat. Cell Biol.
2016 May 9
The transition zone (TZ) ciliary subcompartment is thought to control cilium composition and signalling by facilitating a protein diffusion barrier at the ciliary base. TZ defects cause ciliopathies such as Meckel-Gruber syndrome (MKS), nephronophthisis (NPHP) and Joubert syndrome (JBTS). However, the molecular composition and mechanisms underpinning TZ organization and barrier regulation are poorly understood. To uncover candidate TZ genes, we employed bioinformatics (coexpression and co-evolution) and identified TMEM107 as a TZ protein mutated in oral-facial-digital syndrome and JBTS patients. Mechanistic studies in Caenorhabditis elegans showed that TMEM-107 controls ciliary composition and functions redundantly with NPHP-4 to regulate cilium integrity, TZ docking and assembly of membrane to microtubule Y-link connectors. Furthermore, nematode TMEM-107 occupies an intermediate layer of the TZ-localized MKS module by organizing recruitment of the ciliopathy proteins MKS-1, TMEM-231 (JBTS20) and JBTS-14 (TMEM237). Finally, MKS module membrane proteins are immobile and super-resolution microscopy in worms and mammalian cells reveals periodic localizations within the TZ. This work expands the MKS module of ciliopathy-causing TZ proteins associated with diffusion barrier formation and provides insight into TZ subdomain architecture.