Human respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants. However, host factors that influence disease severity remain incompletely defined. While clinical risk factors are known, identifying genetic susceptibility has been challenging. In this study, we combined human genetics with functional virology to identify host factors that modulate RSV infection and spread. Starting from a cohort of infants hospitalized with severe RSV disease, we prioritized rare coding variants present in homozygous form and predicted to cause strong functional impairment, and selected candidate genes for mechanistic follow-up. Functional interrogation of 23 candidates by CRISPR/Cas9 knockout screening in human lung epithelial cells identified unconventional myosin-X (MYO10), encoding the actin-based motor protein myosin-X, as a critical host factor for RSV. Genetic disruption or siRNA-mediated depletion of MYO10 significantly reduced RSV infectivity, with the strongest effects at post-entry stages of the viral life cycle. Loss of MYO10 impaired filopodia formation, cell migration, and wound healing, leading to altered cell–cell connectivity and restricted viral dissemination. MYO10 depletion reduced both short-range cell-to-cell transmission and longer-distance extracellular spread, resulting in fewer infected cells and diminished accumulation of progeny virus in culture supernatants. In contrast, RSV entry, early gene expression, and interferon responses were unaffected. Finally, a rare homozygous MYO10 motor-domain variant (rs7737765; H148Y), enriched in severe cases, also reduced RSV replication in cell culture—opposite to expectations for a risk allele—yet underscoring biological relevance and suggesting that MYO10 variation may influence disease in vivo through additional effects on epithelial function.
Human respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants. However, host factors that influence disease severity remain incompletely defined. While clinical risk factors are known, identifying genetic susceptibility has been challenging. In this study, we combined human genetics with functional virology to identify host factors that modulate RSV infection and spread. Starting from a cohort of infants hospitalized with severe RSV disease, we prioritized rare coding variants present in homozygous form and predicted to cause strong functional impairment, and selected candidate genes for mechanistic follow-up. Functional interrogation of 23 candidates by CRISPR/Cas9 knockout screening in human lung epithelial cells identified unconventional myosin-X (MYO10), encoding the actin-based motor protein myosin-X, as a critical host factor for RSV. Genetic disruption or siRNA-mediated depletion of MYO10 significantly reduced RSV infectivity, with the strongest effects at post-entry stages of the viral life cycle. Loss of MYO10 impaired filopodia formation, cell migration, and wound healing, leading to altered cell–cell connectivity and restricted viral dissemination. MYO10 depletion reduced both short-range cell-to-cell transmission and longer-distance extracellular spread, resulting in fewer infected cells and diminished accumulation of progeny virus in culture supernatants. In contrast, RSV entry, early gene expression, and interferon responses were unaffected. Finally, a rare homozygous MYO10 motor-domain variant (rs7737765; H148Y), enriched in severe cases, also reduced RSV replication in cell culture—opposite to expectations for a risk allele—yet underscoring biological relevance and suggesting that MYO10 variation may influence disease in vivo through additional effects on epithelial function.
One of the most characteristic morphogenetic processes in Drosophila is the 360° rotation of the male pupal genital disc. This movement is driven by the myosin Myo1D, whose expression in the genital disc is controlled by the Hox gene Abdominal–B. The rotation takes place in contact and relative to the posterior abdomen, yet the contribution of abdominal tissues has remained unclear. Here we show that normal genital disc circumrotation requires active remodeling of posterior abdominal larval epidermal cells that contact the rotating terminalia. Preventing apoptosis in these cells, or increasing EGFR signaling, delays their extrusion and results in incomplete rotation without altering rotational chirality. In parallel, elimination of Extracellular Matrix by Metalloproteinase 1 in these cells, although without leading to their extrusion, is also strictly required for genital disc circumrotation. Inhibition of this metalloproteinase activity leads to persistence of collagen IV and incomplete rotation, revealing an independent requirement for Extracellular Matrix clearance at the disc–abdomen interface. By contrast, genetic conditions that prevent formation or elimination of the male A7 segment do not necessarily impair genital disc rotation, demonstrating that A7 suppression and circumrotation are separable processes. These findings identify posterior abdominal tissue remodeling as an essential extrinsic requirement that enables genital disc circumrotation. ### Competing Interest Statement The authors have declared no competing interest. MICIU/AEI/10.13039/501100011033/, BFU2014-51989-P, BFU2017-86244-P, PID2020-113318GB-I00
Non-muscle cells generate force without forming sarcomeres, building instead highly dynamic, contractile filaments that assemble, remodel, and disassemble in response to mechanical and biochemical signals. This review focuses on the conformational regulation and filament dynamics of myosin II paralogs as they define diverse types of cytoplasmic structures that produce mechanical forces. Whereas muscle myosin II stably resides in sarcomeres and conserve energy by adopting a super-relaxed state in which myosin II heads interact with each other and the core of the thick filament, smooth muscle and non-muscle myosin II shift between a soluble, folded, auto-inhibited 10S species and filaments, where they adopt an extended, assembly-competent 6S form. Phosphorylation of smooth muscle and non-muscle regulatory light chain triggers the conformational transition from 10S to 6S, leading to filament formation and contractile output. Other phosphorylations in the regulatory light and heavy chains also control filament assembly and dynamics through different molecular mechanisms. Biochemical and mechanical inputs fine-tune filament size, lifetime, and duty ratio, shaping contractile output across diverse cellular contexts. Upstream regulators, including biochemical and mechanical inputs, converge on several pathways, e.g., Ca2+/MLCK and RhoA/ROCK, organizing myosin II activity in space and time and enabling the emergence of stress fibers, junctional belts, cortical networks, and contractile rings that support adhesion, migration, cytokinesis, and tissue-level mechanics.
Rxiv cytoskeleton
Rxiv mechanobio