Plk1 regulates centriole length in human cells. (A) Examples of expanded G1 centrioles from cycling cells expressing active Plk1 (Plk1TD). dox, doxycycline. (B) Electron micrographs of centrioles from cycling cells expressing Plk1TD. Centrioles are longer than average with aberrantly positioned appendages. (C) Expanded centrioles from control cycling cells and from cells treated with Plk1 inhibitor GSK from G1. Plot: Quantification of procentriole length using the method described in Fig. 4 E. (D) Electron micrographs of centrioles. Red arrows point to missing and unevenly elongated procentriole MTs. Blue arrow: Procentriole in cross-section lacking a full set of MTs. For more examples of shorter and narrower procentrioles, see Fig. S3. (E) The analysis of cartwheel length by 3D STORM using STIL signal. Cells were immunolabeled for cartwheel protein STIL and imaged by 3D STORM. Cont, control. The length of STIL signals was measured from 3D STORM recordings. Left: Examples of STIL signals of various length. Histogram shows the average length of 3D STORM STIL signals ± SD. Scale bars, 3 µm in A; 0.5 µm in B; 2 µm in C; 0.4 µm in D; 0.2 µm in E. NS, nonsignificant; *, P ≤ 0.05; **, P ≤ 0.001; ***, P ≤ 0.001.