Fig 2: SFI1 is a centriolar protein co‐localizing with Centrin 2 and 3 at the distal tip of centrioles A, BRepresentative confocal images of cycling RPE‐1 cells stained for SFI1 (green) and γ‐Tubulin (magenta) (A) or SFI1 (green) and Centrin 2/3 (magenta) (B). Scale bar: 5 μm. Dashed‐line squares correspond to insets.C, DRepresentative confocal images of expanded centrioles from RPE‐1 cells stained for α/β‐tubulin (αβTub, magenta) and SFI1 (green). Right panels show top view images across the centriolar length confirming the distal localization of SFI1 at centrioles. The white arrowhead indicates SFI1 distal dot at centrioles. Scale bars: 200 and 100 nm (right panels). The average position of SFI1 alongside the centriole is shown in (D).E, FRepresentative confocal images of expanded centrioles from RPE‐1 cells stained for α/β‐tubulin (αβTub, magenta) and Centrin 2/3 (Cetn2/3, gray). Right panels show top view images across the centriolar length confirming the distal localization of Centrin 2/3 at centrioles. The white arrowhead indicates Centrin 2/3 distal dot at centrioles. Scale bars: 200 and 100 nm (right panels). The average position of Centrin 2/3 alongside the centriole is shown in (F).G, HRepresentative confocal images of expanded centrioles from RPE‐1 cells stained for α/β‐tubulin (αβTub, magenta) and Centrin 3 (Cetn3, cyan). Right panels show top view images across the centriolar length confirming the distal localization of Centrin 3 at centrioles. The white arrowhead indicates Centrin 3 distal dot at centrioles. Scale bars: 200 and 100 nm (right panels). The average position of Centrin 3 alongside the centriole is shown in (H).I, JRepresentative confocal images of expanded centrioles from RPE‐1 cells stained for α/β‐tubulin (αβTub, magenta), SFI1 (green), and Centrin 2/3 (Cetn3, gray). Right panels show top view images confirming the distal localization of SFI1 and Centrin 2/3 at centrioles. Scale bars: 200 and 100 nm (right panels). The average position of SFI1 and Centrin 2/3 alongside the centriole is shown in (J).K, LPosition of SFI1 and Centrin signals at the distal centriolar region in nm either from separated stainings (K) or co‐stainings (L). Data information: Average ± SD, N, statistical analysis: (D) N = 42 centrioles from three independent experiments. (F) N = 26 centrioles from three independent experiments. (H) N = 25 centrioles from three independent experiments. (J) N = 54 centrioles from three independent experiments. (K) SFI1 = 376 ± 18 nm; Centrin 2/3: 355 ± 36 nm; and Centrin 3: 359 ± 37 nm. N = 41, 25, and 24 centrioles for SFI1, Centrin 2/3, and Centrin 3, respectively, from two independent experiments. One‐way ANOVA followed by Bonferroni post hoc test (SFI1 vs. Cetn2/3 P = 0.0196, SFI1 vs. Cetn3 P = 0.0702, and Cetn2/3 vs. Cetn3 P = 0.999). (L) SFI1 = 316.3 ± 43.8 nm and Centrin 2/3: 351.8 ± 42.6 nm. N = 53 centrioles from three independent experiments. Unpaired t‐test (SFI1 vs. Cetn2/3 **P < 0.0001).