Figure 6.

Multicolor SMLM suggests endosomal mRNA escape at the nanoscale from transferrin-containing tubules in primary human adipocytes and HeLa cells. Exemplary images of the different observable types of Cy5-mRNA (magenta) escape in primary human adipocytes and HeLa cells relative to transferrin-positive tubules (green) and EGF (cyan). (A) Concentrated mRNA signal is located at the very tip of a transferrin-positive tubule, connected to an elongated mRNA signal colocalizing along the tubule. Very sparse mRNA signal can be detected outside the tubule. (B) Disperse Cy5-mRNA is seemingly emanating from the transferrin-positive tubule from which it is already segregated. These patterns clearly do not constitute intact LNP and are likely to represent partly stretched mRNA molecules escaping from endosomal structures. (C) An LNP is located on a long transferrin-positive tubule together with a perpendicular dispersed Cy5-mRNA signal, likely representing an instance of Cy5-mRNA escape. (D) In very rare cases, also in arrested endosomes (compare Fig. 4), dispersed mRNA signal attached to a transferrin-positive structure can be detected. ROIs indicating the cellular context of displayed endosomes are provided in Supplemental figures, Figs. S15, S17, S18, S19, S20, S21, S22, S23, S24, S25, and S26. Zoom-in of the indicated regions are presented in the right-side panels. Scale bars are 100 nm.