Figure 3.

(A) Representative images of the ER (left column, red) and the superimposed ERES pattern (right column, green) in cells in which lunapark proteins have been depleted by RNAi. Scale bars, 10 μm. Close-ups in the inset reveal that the ER has lost its network-like morphology, whereas superimposed ERESs have considerably grown in size. Scale bars, 2 μm. (B) The associated PDF of apparent ERES occupation areas, p(A), deviates strongly from the lognormal shape found for untreated cells (solid line), featuring a marked tail for large values of (A). Consequently, the number of clusters (ERESs with more than 150 pixels) is strongly enhanced (see also main text and Table 1). Displaying the same data in a double-logarithmic fashion (Document S1. Figs. S1–S7, Document S2. Article plus supporting materialD) further emphasizes the significant changes upon depleting lunapark proteins. (C) The PDF of apparent occupation areas of ER fragments after filipin treatment (gray histogram) or osmotic shock (red histogram) has a marked peak around 0.6 μm², revealing that these host membranes are large enough to host ERESs without restricting their native size (solid black line indicates the lognormal PDF of native ERESs, as also included in Fig. 3B). To see this figure in color, go online.