Expansion microscopy of apicomplexan parasites

Abstract

Apicomplexan parasites comprise significant pathogens of humans, livestock and wildlife, but also represent a diverse group of eukaryotes with interesting and unique cell biology. The study of cell biology in apicomplexan parasites is complicated by their small size, and historically this has required the application of cutting‐edge microscopy techniques to investigate fundamental processes like mitosis or cell division in these organisms. Recently, a technique called expansion microscopy has been developed, which rather than increasing instrument resolution like most imaging modalities, physically expands a biological sample. In only a few years since its development, a derivative of expansion microscopy known as ultrastructure‐expansion microscopy (U‐ExM) has been widely adopted and proven extremely useful for studying cell biology of Apicomplexa. Here, we review the insights into apicomplexan cell biology that have been enabled through the use of U‐ExM, with a specific focus on Plasmodium, Toxoplasma and Cryptosporidium. Further, we summarize emerging expansion microscopy modifications and modalities and forecast how these may influence the field of parasite cell biology in future.

The initiation and early development of the tubulin-containing cytoskeleton in the human parasiteToxoplasma gondii

“…By expanding biological samples in a hydrogel, Expansion Microscopy (ExM) has enabled the visualization of structural details much smaller than the resolution limit of conventional light microscopy [36][37][38][39][40]. The ExM method [38] has been applied in investigating subcellular details of apicomplexans (reviewed in [41]). Here we use a slightly modified version of this method to determine the arrangement of tubulin containing structures in developing daughters.…”

PlasmodiumRON11 triggers biogenesis of the merozoite rhoptry pair and is essential for erythrocyte invasion

“…Rhoptry biogenesis remains a poorly understood process, primarily due to the small size of P. falciparum ’s rhoptries, which, coupled with the limited resolution offered by conventional microscopy, has made their study challenging. Recent advances in microscopy techniques, such as UExM, have opened new possibilities for exploring these micron-sized secretory organelles (Liffner and Absalon 2023). Using UExM, we observed that RON11 is required for the proper biogenesis of rhoptry pairs, as its absence led to merozoites with single rhoptries, an unprecedented phenotype that has not been observed in any other apicomplexan system.…”

Mosquito Tissue Ultrastructure-Expansion Microscopy (MoTissU-ExM) enables ultrastructural and anatomical analysis of malaria parasites and their mosquito

“…Importantly for its use in single-celled organisms, U-ExM results in near-native preservation of cellular ultrastructure and 4 to 4.5-fold isotropic expansion 4 . U-ExM has been widely adopted in the study of the cell biology of apicomplexan parasites 13 .…”

“…U-ExM has been widely adopted in the study of the cell biology of apicomplexan parasites 13 . Apicomplexa are a phylum of largely parasitic single-celled organisms that include significant causes ofdisease in humans and livestock, such as malaria, toxoplasmosis and cryptosporidiosis.…”