Imaging nanoscale nuclear structures with expansion microscopy

Commonly applied super-resolution light microscopies have provided insight into subcellular processes at the nanoscale. However, imaging depth, speed, throughput and cost remain significant challenges, reducing the numbers of three-dimensional, nanoscale processes that can be investigated and the number of laboratories able to undertake such analysis. Expansion microscopy solves many of these limitations but its application to imaging nuclear processes has been constrained by concerns of unequal nuclear expansion.

Here we demonstrate the conditions for isotropic expansion of the nucleus. Using DNA damage response proteins, BRCA1, 53BP1 and RAD51 as exemplars we quantitatively describe the three-dimensional nanoscale organisation of over 50,000 DNA damage response structures. We demonstrate the ability to assess chromatin regulated events and show the simultaneous assessment of four elements. This study thus provides the means by which expansion microscopy can contribute to the investigation of nanoscale nuclear processes.