CEP164 localizes to BB docked at the inner segment membrane.

A, immunolocalization of CEP164 (red) in P21 Cep164+/+;Egfp-Cetn2 (green) photoreceptors. CEP164 is an inner segment protein associating with basal bodies (BBs). B, BB enlargement with connecting cilium (CC) and daughter centriole (DC). Expression of transgenic Egfp-CETN2 identifies the CC, BB (= mother centriole, MC) and DC. C, BB docking pathway, ciliogenesis and IFT. a, centrosome consisting of MC and DC; MC and DC distal ends are capped by CP110/CEP97 (green). b, MC acquires distal appendage proteins (DAPs, light blue) and CEP164 (red). c, TTBK2 (tau tubulin kinase 2) phosphorylates DAPs which removes the terminal cap and allows docking. MC matures to BB. d, BB cap removal permits extension of A- and B-tubules to form an axoneme and transition zone (TZ). e, BB/TZ acquire IFT proteins and kinesin-2 to assist IFT. f, IFT delivers subunits to extend the axoneme and initiate disc morphogenesis. g, deletion of CEP164 post-ciliogenesis leads to loss of IFT protein and cell death. (TIF)