SPATA7 extends AHI1 localization apical of the TZ in primary cilia. (a) Endogenous AHI1 (white) localizes at the TZ of the primary cilium, marked by acetylated α-tubulin in hTERT-RPE1 cells (left). Ectopic expression of hSPATA7-GFP (right) induces apical extension of the endogenous AHI1 localization signal beyond the TZ into the ciliary axoneme (subsets display zoomed images of AHI1 [white], acetylated α-tubulin [red], SPATA7-GFP, and DAPI). Bars: (main images) 10 µm; (insets) 2 µm. (b) Model displaying the CC zones PSTZ at the DCC and PCC that are visible in the Spata7 mutant retinae. The CC is comprised of PCC, a region homologous to the TZ of the primary cilium, and PSTZ, a specialized photoreceptor-specific zone of the CC that is crucial for maintenance of the CC microtubule core. OS, outer segment.