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Gwendal Guerin1*, Tapas Singha1*, John Manzi1, Sophie Brasselet2, Julien Berro3, Manos Mavrakis2, Jean-Francois Joanny1, Carles Blanch Mercader1** and Feng-Ching Tsai1** Institut Curie, Université PSL, Sorbonne Université, CNRS UMR168, Laboratoire Physico-Chimie Curie, 75005 Paris, France Institut Fresnel, CNRS UMR7249, Aix Marseille Univ, Centrale Marseille, Marseille, France Molecular Biophysics & Biochemistry, Yale University, New Haven, Connecticut, United States. Cell Biology, Yale University School of Medicine. *Equal contribution **Corresponding authors Topological defects in nematic actin organizations are recognized as key mechanical regulators of tissue morphogenesis. However, how myosin motor activity modulates these defects in actin nematics is not fully understood. Here, we investigated how myosin I motors re-organize dense, nematically ordered actin filaments and influence the emergence of topological defects. Myosin I functions as an actin-membrane linker, exerting forces on actin filaments while anchoring them to membranes. Using reconstituted systems in which nematic actin networks are coupled to supported lipid membranes via myosin I motor Myo1b, we showed that Myo1b drives actin filament accumulation at +1/2 comet-like topological defects. This filament accumulation leads to the formation of protrusion-like actin structures. Fluorescence polarization microscopy reveals that actin filaments within these defects are highly aligned and densely packed. We proposed that the comet head of the +1/2 defects acts as a physical barrier that impedes filament transport toward the defect core, resulting in filament accumulation at the comet tail. To elucidate the underlying physical mechanism, we developed a microscopic model of Myo1b-driven actin filament transport and solve it by numerical simulations. The model quantitatively reproduces actin accumulation near the comet head of +1/2 defects, in good agreement with our experimental observations.