Fig. 8.
The N-terminal Fn1 assembly domain regulates the organization of Fn1 nanodomains into linear fibrillar arrays. Fn1mEGFP/+ MEFs were plated on glass and were either left untreated (A–A2) or incubated with the control III-11C peptide (B–B2) or the FUD peptide (C–C2). Cells were fixed, stained without permeabilization and imaged using SMLM protocol II. Boxes marked 1 and 2 in A,B are magnified in A1,B1 and in A2,B2, respectively. The box in C is magnified in C1 and C2. Arrows in A1,B1 point to Fn1 nanodomains (NDs) in fibrils. Arrows in C1 point to non-fibrillar (NF) nanodomains, which are magnified in C2. Images are representative of three independent experiments. Scale bars: 5 μm (A–C); 500 nm (A1–C1); 100 nm (A2–C2). (D) Quantification of grouped Fn1 localizations in nanodomains. Red lines mark medians, black lines indicate the quartiles. Differences are not statistically significant, determined by Kruskal–Wallis test with Dunn's correction for multiple testing. (E) Models of Fn1 fibril formation. (E1,E2) Nanodomain periodicity in fibrils might be due to an extended Fn1 dimer (E1) or Fn1 subunits (E2). Fn1 molecules are colored according to the scheme shown in Fig. S3D, mEGFP is marked in green, and C-terminal disulfide bonds in red.