Cell-intrinsic and -extrinsic functions of the ESCRT-III component Shrub in cytokinetic abscission of Drosophila Sensory Organ precursor

While the molecular mechanisms underlying the abscission of isolated cells are largely decrypted, those of fast-cycling, epithelial progenitors surrounded by epidermal cells (ECs) connected by junctions remain largely unexplored. Here, we investigated the remodeling of the permeability barrier ensured by septate junctions (SJs) during cytokinesis of Drosophila sensory organ precursor (SOP). We report that SOP cytokinesis involves the coordinated polarized assembly and remodeling of SJs in the dividing cell and its neighbors, which remained connected via membrane protrusions pointing toward the SOP midbody. SJs assembly and midbody basal displacement occur more rapidly in SOP than in ECs, leading to a faster disentanglement of the protrusions that precedes midbody release. As reported in isolated cells, the endosomal sorting complex required for transport-III component Shrub/CHMP4B is recruited at the midbody and cell-autonomously regulates abscission. In addition, we found that Shrub is recruited to membrane protrusions, is required for SJ integrity, and that alteration of SJ integrity leads to premature abscission. Our study uncovers cell-intrinsic and -extrinsic functions of Shrub in epithelial abscission to support the coordination of permeability barrier maintenance and abscission in SOPs.