aPKC and F-actin Dynamics Promote Hippo Pathway Polarity in Asymmetrically Dividing Neuroblasts

The Hippo signaling pathway is conventionally known to restrict tissue growth in animals. Genetic studies have also shown that loss of Hippo pathway components leads to defects in asymmetric cell division in Drosophila neural stem cells, known as neuroblasts. The hallmark of neuroblast division is the asymmetric localization of aPKC/Bazooka (Par3)/Par6 complex, termed the Par complex, to the apical cell cortex. However, the localization of the Hippo pathway components in neuroblasts remains unknown. Here, we report that two key activators of the Hippo pathway, Kibra and Salvador, polarize to the apical cortex of mitotic neuroblasts. We show that apical polarity, via the activity of aPKC, and F-actin dynamics synergize to drive Kibra polarization. Together, these results suggest how Hippo pathway output may be influenced by apical polarity and the F-actin cytoskeleton and provide mechanistic insight into how the pathway's activity in neuroblast asymmetric division is regulated.