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

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 <i>de novo</i> variants in human cytoskeletal β-actin (<i>ACTB</i>) and γ-actin (<i>ACTG1</i>) 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 <i>C. elegans</i> cytoplasmic actin orthologue <i>act-2</i> 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 behavioral phenotypes. Notably, the severity of the observed defects correlates with the severity of patients' symptoms. Thus, we provide evidence that such <i>C. elegans</i> models are relevant to investigate the mechanisms underlying NMA physiopathology and could ultimately be used to screen for therapeutic strategies.