A120 - Nanoscale imaging of the Toxoplasma gondii microtubules network using Expansion microscopy and 3D-STED

Bastien Touquet (???)
Eric Denarier (eric.denarier@univ-grenoble-alpes.fr)

Toxoplasma gondii is an elliptical shaped-cell of about 5 to 7 µm length in the major axis and 2 µm in the minor one, featured by a distinctive apical and basal pole. In particular, the apical pole comprises a structure known as the conoid, a truncated cone complex of 280 nm in length and 380 nm in diameter composed of curved tubulin fibers, with apical rings in its basis. Given its size, to characterize the architecture of this structure, super-resolution techniques are necessary. Between those techniques, Expansion microscopy (ExM) has emerged as a low-cost and powerful option. ExM consists in physically expanding a swellable gel-embedded biological specimens to overcome the resolution limit of light microscopy. Several protocols are now available wherein the sample can be expanded by 4 to 10 fold to obtain a resolution between 70 to 25 nm. The 4-fold expansion protocols are the more extended and easy to use and recent combination with optical super-resolution like STED show a resolution gain below 10 nm. In this workshop, through the tubulin labeling of the conoid structure, we will show two types of 4-fold ExM protocols (ProExM from Boyden Lab and U-ExM from Guichard Lab) with technical manipulations for the participants. The attendees will critically analyze the samples with respect to labeling quality of both protocols, to later discuss and select one ExM sample for optical super resolution acquisition (STED) and appreciate the resolution gain between non expand and expand biomolecules.