Correlative light and electron microscopy reveals fork-shaped structures at actin entry sites of focal adhesions

Karin Legerstee, Jason Sueters, Tsion E. Abraham, Johan A. Slotman, Gert Jan Kremers, Jacob P. Hoogenboom, Adriaan B. Houtsmuller

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Focal adhesions (FAs) are the main cellular structures to link the intracellular cytoskeleton to the extracellular matrix. FAs mediate cell adhesion, are important for cell migration and are involved in many (patho)-physiological processes. Here we examined FAs and their associated actin fibres using correlative fluorescence and scanning electron microscopy (SEM). We used fluorescence images of cells expressing paxillin-GFP to define the boundaries of FA complexes in SEM images, without using SEM contrast enhancing stains. We observed that SEM contrast was increased around the actin fibre entry site in 98% of FAs, indicating increases in protein density and possibly also phosphorylation levels in this area. In nearly three quarters of the FAs, these nanostructures had a fork shape, with the actin forming the stem and the high-contrast FA areas the fork. In conclusion, the combination of fluorescent and electron microscopy allowed accurate localisation of a highly abundant, novel fork structure at the FA-actin interface.

Original languageEnglish
Number of pages7
JournalBiology open
Issue number11
Publication statusPublished - 2022

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • Cell migration
  • Correlative microscopy
  • Electron microscopy
  • Fluorescence microscopy
  • Focal adhesions


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