Figure 4. TTBK2 acts upstream of IFT and CP110.

(A) IFT140 (green), an IFT-A complex protein, localizes primarily to the transition zone in WT and can be seen at lower levels in the axoneme. IFT140 is present at the mother centriole (red, γ-tubulin) in Kif3a^-/- MEFs, but is not detectable at the Ttbk2^bby centrosomes. 56 Ttbk2^bby, 17 Kif3a^-/- and 27 WT cells were examined. (B) The IFT-B complex component IFT88 (green) localizes to transition zone and ciliary axoneme in WT MEFS and to the mother centriole (red) in Kif3a^-/- MEFs, but is not associated with the centrosomes of Ttbk2^bby cells. Centrosomes are labeled with γ-tubulin (red). 52 Ttbk2^bby cells, 21 Kif3a^-/-- and 31 WT cells were examined. (C) CP110 (green) is present on the distal end of the WT daughter centriole (red), the centriole that does not template the ciliary axoneme (purple). CP110 is detected on one of the two centrosomes in Kif3a^-/- MEFs. In Ttbk2^bby cells, CP110 is present on both centrosomes in most cells. Scale bar is 2 μm. (D) The percentage of cells with CP110 seen on both centrosomes in WT (white bar, 16.0+/-5.2) and Ttbk2^bby (black bar, 88.8+/-3.6) MEFs. Error bars represent the SEM. p < 0.0001, 5 fields of cells were counted for a total of 114 Ttbk2^bby and 116 WT cells. Please see Figures S3 and S4 for additional images.