Fig. 4.

Possible structural relationship between the ciliary pore and the transition zone. a Electron cryotomography reveals nine pores (outer channels) in isolated basal bodies from Tetrahymena. Each outer channel is located adjacent to a doublet microtubule (MT) and may be a pore for the entry of ciliary components. Reprinted from Ounjai et al. [91], with permission from Elsevier. b Schematic drawings of the putative arrangement of the CPC and Y-link structures. The CPCs are comprised of scaffold and central NUPs and form a barrier for entry of cytosolic proteins, whereas the Y-links are comprised of NPHP, MKS, and JBTS proteins and form a barrier for entry of membrane proteins. NPHP nephronophthisis, MKS Meckel–Gruber syndrome, JBTS Joubert syndrome, MT microtubule