FAP76 is a C1c protein with multiple connections to neighboring structures. (A–H) The comparison of tomographic slices (A, B, E, and F) and isosurface renderings (C, D, G, and H) between the averaged CA repeats of WT (A–D) and fap76-1 axonemes (E–H) viewed in cross-sectional (A, C, E, and G) and longitudinal (B, D, F, and H) orientations shows a triskelion-shaped structure that is present in the WT C1c projection (magenta brackets and arrowheads in A–D) but missing in fap76-1 (white brackets and arrowheads in E–H). The thin blue line in A indicates the location of the tomographic slices shown in B and F. (I and J) The isosurface rendering of a difference map between the averaged CA of WT and fap76-1 shows the triskelion-shaped FAP76 densities (magenta) in longitudinal view superimposed on the averaged CA of fap76-1 (gray) in overview (I) and zoomed-in (J, location indicated by box in I). Note the three connections (magenta arrowhead and #1–3) of FAP76 with neighboring structures, i.e., #1 with the C1c projection close to C1e (I), and #2 and #3 with C1d densities (yellow in J). Scale bar in F, 20 nm (valid for A, B, E, and F).