Figure 3.

Super-resolution microscopy uncovering narrow IFT88 leakage toward the basal body (BB) in TCTN2^−/− cells. (A) IFT88 distributions are shown relative to the distal appendage (DAP) protein SCLT1. IFT88 molecules typically localize to the DAPs, the transition zone (TZ), and the cilium in wild-type (WT) cells. A narrow extension of IFT88 toward the BB (pointed by a yellow arrowhead), potentially within the width of the BB axoneme, is observed in each of these representative TCTN2^−/− cilia. This IFT extension is absent in WT and FBF1^−/− cilia. Inset: an EM image of a WT RPE1 cell marks the TZ (blue), DAPs (green), and BB (yellow) used to be overlaid in each cilium image for dimensional comparison. (B) Extension of IFT144 toward the BB lumen of TCTN2^−/− RPE1 cells is observed in a single cilium (upper) and an overlaid image of multiple cilia (n = 5) (lower). (C) Extension of IFT88 toward the BB lumen of RPGRIP1L siRNA knockdown cells is shown. (D) Overlaid results from the data set in (A) show narrow IFT88 leakage into the BB (potentially the BB lumen) in TCTN2^−/− cells, which is not observed in WT or FBF1^−/− cells. (E) The intensity profiles of (D) along the ciliary central axis show the <500 nm IFT88 extension toward the BB in TCTN2^−/− cells. (F) FWHM of the overlaid image in (D) at each longitudinal position shows the narrow width of IFT extension toward the BB in TCTN2^−/− cells. A decreased lateral distribution in the TZ of TCTN2^−/− cells is also observed. To see this figure in color, go online.