Actin dynamics during contractile ring assembly drives mitotic nuclear displacement in fission yeast

Nuclear positioning during mitosis is crucial for cell survival, yet its regulation remains unclear. We previously observed that, during a prolonged mitotic arrest in fission yeast, the nucleus becomes displaced from the cell center in an actin-dependent manner. Here, we examined the role of actin cable dynamics in nuclear displacement, which is essential for contractile actomyosin ring (CAR) assembly. Time-lapse imaging revealed that nuclear movement begins before CAR formation. Further genetic analysis indicated that proper CAR assembly is a prerequisite for mitotic nuclear displacement. Forced tethering of the actin-cable-nucleator formin to the nuclear pore component altered actin cable localization and abolished nuclear displacement, underscoring the importance of non-medial actin cable transport required for CAR assembly. These findings demonstrate that nuclear displacement is driven by the spatial organization of actin cables during CAR assembly, providing new insight into the mechanical regulation of nuclear positioning.