The Drosophila myosin VI Jaguar is required for basal protein targeting and correct spindle orientation in mitotic neuroblasts

Asymmetric cell divisions generate cellular diversity. In Drosophila, embryonic neuroblasts target cell fate determinants basally, rotate their spindles by 90 degrees to align with the apical-basal axis, and divide asymmetrically in a stem cell-like fashion. In this process, apically localized Bazooka recruits Inscuteable and other proteins to form an apical complex, which then specifies spindle orientation and basal localization of the cell fate determinants and their adapter proteins such as Miranda. Here we report that Miranda localization requires the unconventional myosin VI Jaguar (Jar). In jar null mutant embryos, Miranda is delocalized and the spindle is misoriented, but the Inscuteable crescent remains apical. Miranda directly binds to Jar, raising the possibility that Miranda and its associated proteins are translocated basally by this actin-based motor. Our studies demonstrate that a class VI myosin is necessary for basal protein targeting and spindle orientation in neuroblasts.