Extended Data Fig. 7: Changes in ER curvature within ERMCSs.
From: Motion of VAPB molecules reveals ER–mitochondria contact site subdomains
a, Single slices through the longitudinal (parallel to the central cylindrical axis of the structure) and perpendicular axes of a representative ERMCS or a neighboring ER control in the cytoplasm. Red lines indicate the location of the ER membrane. These are single representative images of n = 39 (ER tubules) or n = 25 (ERMCSs) collected through the two FIB-SEM volumes. b, Schematic of the ER cross sections in a and their methods of analysis. Note that in the longitudinal sections, ER membrane curvature (κ) is largely neutral, but in the perpendicular sections it can be highly positively curved (curving towards ER lumen) or negatively curved (curving away from ER lumen). The radius of curvature (R) is inversely proportional to the degree of curvature (κ). c, The radius of curvature of the ERMCS and isolated ER in the FIB-SEM volumes. Isolated ER controls are selected within 5 μm of each ERMCS (n = 39 tubules, 25 ERMCSs; p < 0.0001; two-sided Mann Whitney test). Error bars represent the median and 95% confidence interval for the median. d, Curvature along the parallel or perpendicular dimensions of the ERMCS or local ER controls as demonstrated in b. e, Local ER curvature as calculated in three dimensions on the triangulated mesh generated from the surface of the ER membrane in a representative FIB-SEM volume. Sites of contact with mitochondria (not shown for clarity) are traced with dotted lines and indicated with black arrows. The blue arrow indicates a site of direct contact with a mitochondrion facing away from the viewer. f, Relative mean local curvature of ERMCS- or non-CS-associated ER membrane as calculated from the triangulated surface in the two volumes shown in Extended Data Fig. 1 and normalized to median value in the ERMCSs. Dotted lines in the plots show the median and quartiles. (ERMCS data is n = 133,494 [vol1] or n = 37,062 [vol2] triangulated faces within ERMCSs, control ER is n = 500,000 triangulated faces selected randomly from the ER outside the ERMCSs in the matched volume. P-values are approximated from the z distribution of a Kruskal-Wallis test using two-sided Dunn’s multiple comparisons test to adjust direct comparisons for multiplicity). Scale Bars: 200 nm.
