Kin17 drives dissociation of Mira from the centrosome in neuroblasts by regulating splicing of Flfl

During asymmetric division of Drosophila neuroblasts, the fate determinant Prospero and its adaptor Miranda are segregated to the basal cortex through aPKC phosphorylation of Miranda and displacement from the apical cortex. Here we identify Kin17 as a novel regulator of Miranda localization during asymmetric cell division and loss of Kin17 or Protein Phosphatase 4 leads to aberrant localization of Miranda to the centrosome and cytoplasm and Prospero to the centrosome and nucleus. We report that dephosphorylation of Mira by Protein Phosphatase 4 at Serine-96 at the centrosome is required for the proper basal localization of Mira after being phosphorylated at the apical cortex. We further demonstrate that Kin17 regulates Miranda localization by promoting splicing of the transcript of a PP4 component Falafel. Taken together, our work reveals a novel mechanism that ensures proper basal localization of Miranda by preventing its aberrant localization to the centrosome during the asymmetric division. SummaryConnell et al. show that proper segregation of cell fate determinant Miranda requires PP4-mediated dissociation of Miranda from the centrosome/spindle in Drosophila neuroblasts, a critical step that has been overlooked previously. Further, they identify a novel regulator of Miranda localization, Kin17, which promotes splicing of the transcript of the PP4 component Falafel.