A kinesin Klp10A mediates cell cycle-dependent shuttling of Piwi between nucleus and nuage

The piRNA pathway, which protects germline genomes from selfish elements such as transposons, operates in two modes: 1) cleavage of transcripts of selfish elements in the cytoplasm, and 2) their transcriptional silencing in the nucleus. Here we describe a novel mechanism by which these two modes exchange the information. We show that the nuclear subpathway component Piwi interacts with the nuage, the compartment that mediates the cytoplasmic subpathway, during mitosis of Drosophila spermatogonia. At the end of mitosis, Piwi leaves nuage to return to the nucleus. We found that dissociation of Piwi from nuage occurs at the depolymerizing microtubules of the central spindle, mediated by a microtubule-depolymerizing kinesin Klp10A. When Piwi’s return to the nucleus is delayed upon klp10A depletion, piRNA production is impacted, suggesting the importance of nuclear-cytoplasmic communication in piRNA biogenesis. We propose that cell cycle-dependent communication of piRNA subpathways plays important roles in coordinated piRNA production. We performed biological triplicate small RNA-seq and mRNA-seq in  wild-type and klp10A-knockdown germ cells (nos-gal4>UAS-klp10ARNAi).