Super-resolution Microscopy at its Best

Immerse deeper and deeper into the inner world of cells with the microscope. Imaging the nucleus and other structures more and more accurately. Get the most detailed views of cellular multiprotein complexes. All of these are goals pursued by the microscopy expert Markus Sauer at the Biocenter of the Julius-Maximilians-Universität Würzburg (JMU). Together with research teams from Geneva and Lausanne, he has now shown that a hitherto doubted method of high-resolution super-resolution microscopy is reliable.

We are talking about ultrastructural expansion microscopy (U-ExM). In a nutshell, it works like this: The cell structures to be imaged, in this case multi-protein complexes, are anchored in a polymer - just like putting candles in an Advent wreath or decorating a Christmas tree.

Cell structures are not distorted

Then the interactions between the proteins are destroyed and the polymer is swelled with liquid. "The polymer then expands evenly in all spatial directions by a factor of four. The antigens are retained and can subsequently be stained with dye-labeled antibodies, "says Professor Sauer. So far, many in science have been of the opinion that the expansion of the polymer does not proceed evenly and one gets a distorted representation in the end.

"With U-ExM, we can really show ultrastructural details, the method is reliable," says Sauer. "And we get with her a picture that is four times higher than the standard methods of microscopy."

Centrioles were the start

The research team is currently proving this in the journal "Nature Methods" using the example of the centrioles. These cylindrical protein structures play an important role in cell division; The Würzburg biologist Theodor Boveri first described it in 1888.

The centrioles were chosen for the experiment because their structure is already well known. "In comparison to electron micrographs, we were able to see that U-ExM works reliably and even preserves the chirality of the microtubule triplets that make up the centrioles," explains Sauer.

Next, the researchers at JMU want to use this method of microscopy to analyze cell structures of which one has not yet had such a precise picture. "These are for example substructures of the centrioles, the nuclear pore complexes or synaptonemal complexes. All of them are now accessible for the first time with molecular resolution instead of light microscopy, "said Sauer.

This article has been republished from materials provided by Julius-Maximilians-Universität Würzburg. Note: material may have been edited for length and content. For further information, please contact the cited source.

Reference
Imaging cellular ultrastructures using expansion microscopy (U-ExM), Nature Methods, December 17, 2018, DOI 10.1038 / s41592-018-0238-1.