In-vivo high resolution AFM topographic imaging of Caenorhabditis elegans reveals previously unreported surface structures of cuticle mutants

Atomic force microscopy (AFM) is a powerful method for topographic imaging of surfaces with nanometer resolution. AFM offers significant advantages over scanning electron microscopy (SEM) including the acquisition of quantitative 3D-images and biomechanical information. More importantly, for in-vivo biological imaging, AFM does not require sample dehydration/labeling. We show for the first time high-resolution topographical images of the cuticle of the model organism C. elegans under physiological conditions using AFM. C. elegans is used extensively for drug screening and to study pathogen adherence in innate immunity; both applications highly depend on the integrity of the nematode's cuticle. Mutations affecting both drug adsorption and pathogen clearance have been proposed to relate to changes in the cuticle structure, but never visually examined in high resolution. In this study we use AFM to visualize the topography of wild-type adult C. elegans as well as several cuticle collagen mutants and describe previously unseen anatomical differences.

Graphical AbstractThe model organism C.elegans is used for a range of medical research applications including drug screening and the study of host-pathogen interactions. Mutations in cuticle proteins affect the integrity of the cuticle and therefore the efficiency of both applications, but the details remain poorly understood. We have developed an AFM-protocol that allows us to acquire topographic images of the nematode's cuticle at nanometer spatial resolution under physiological conditions. We apply our method to reveal previously unreported surface structure in the cuticle of known collagen mutants whilst simultaneously investigating the biomechanical properties of individual surface components.260