(A) Representative ‘side views’ of rendered MTs in single tomograms of individual K-fibers from control (left, red, Video 2) or TACC3 OE (right, blue, Video 3) cells. Tomogram thickness, 66.4 nm (Control) trimmed to 34.2 nm, 34.2 nm (TACC3 OE). For scale, MTs are 25 nm in diameter. (B) Aide memoire of the spherical coordinate system. Trajectories of MTs (green line) in K-fibers were defined and normalized via Euler's rotation (see ‘Materials and methods’) such that the overall trajectory of all fibers pointed to the zenith. Measurements of polar angle (θ) and azimuthal angle (φ) were made from the normalized sets and are presented in C–E. (C) Violin plots of the polar angles for MTs in K-fibers from control and TACC3 overexpressing cells. Box plots show the median, 75th and 25th percentile, and whiskers show the minimum and maximum. Violins show a kernel density estimate of the data and are trimmed to the minima and maxima. Comparison of the median MT angle from each K-fiber, Wilcoxon Rank Sum Test, p = 0.007, Nfiber = 12–15. (D) Illustration of the deviation of MTs from the fiber axis caused by TACC3 overexpression. Cartesian coordinates of the intersection of individual MT vectors that start from a common origin (0, 0, 0), with an x-y plane at z = 100 nm. To account for the difference in number of MTs, the insets show a normalized 2D histogram of these coordinates cropped to a 40 × 40 nm square centered at 0, 0, 100. (E) Plots of azimuthal angle (above) and polar angle (below) as a function of distance from the fiber center (defined as described in the ‘Materials and methods’). Line of best fit is shown with 95% confidence bands (dashed line), r2 = 0.07 (control), and 0.007 (TACC3 overexpression).