Multiscale characterization of Caenorhabditis elegans mutants to probe functional mechanisms of human actin pathological variants

SUMMARY Actin plays a crucial role in diverse physiological processes by forming dynamic networks that determine cellular shape and mechanical properties. Non-Muscle Actinopathies (NMA) are rare diseases caused by de novo variants in human cytoskeletal β-actin ( ACTB ) and γ-actin ( ACTG1 ) genes, ranging from missense mutations to whole gene deletions. Currently, the high clinical variability and genotype-phenotype correlations in NMA remain largely unresolved. To address this concern, we inserted nine mutations identified in patients in the C. elegans cytoplasmic actin orthologue act-2 and performed a quantitative multiscale characterization of these animal models. We uncovered various perturbations including micro-scale actin network defects, cell-scale abnormalities, morphogenesis failure, and weaker behavioural phenotypes. Notably, the severity of the observed defects correlates with the severity of patients’ symptoms. Thus, we provide evidence that such C. elegans models are relevant to investigate the mechanisms underlying NMA physiopathology and could ultimately be used to screen for therapeutic strategies.