Abstract
ABSTRACTIn epithelia, mitotic cells round up and push against their neighbors to divide. Mitotic rounding results from increased assembly of F-actin and cortical recruitment of Myosin II, leading to increased cortical stability. Whether this process is developmentally regulated is not well known. Here, we examined the regulation of cortical stability in Sensory Organ Precursor cells (SOPs) in the Drosophila pupal notum. SOPs differed in apical shape and actomyosin dynamics from their epidermal neighbors prior to division, and appeared to have a more rigid cortex at mitosis. We identified RhoGEF3 as an actin regulator expressed at higher levels in SOPs, and showed that RhoGEF3 had in vitro GTPase Exchange Factor (GEF) activity for Cdc42. Additionally, RhoGEF3 genetically interacted with both Cdc42 and Rac1 when overexpressed in the fly eye. Using a null RhoGEF3 mutation generated by CRISPR-mediated homologous recombination, we showed using live imaging that the RhoGEF3 gene, despite being dispensable for normal development, contributed to cortical stability in dividing SOPs. We therefore suggest that cortical stability is developmentally regulated in dividing SOPs of the fly notum.
Highlights
Epithelia function as protective and selective barriers between the external world and the body interior
We identified RhoGEF3 as a protein expressed at higher levels in Sensory Organ Precursor cells (SOPs)
Using an in vitro assay, we found that a large 60 kDa fragment of RhoGEF3 encompassing the catalytic DH-PH domains could act as a Cdc42 GTPase Exchange Factor (GEF)
Summary
Epithelia function as protective and selective barriers between the external world and the body interior. Cells adopt various shapes and dimensions at interphase: cells can be elongated in columnar and pseudostratified epithelia, or be flat in squamous epithelia Despite these morphological differences, cells adopt at mitosis a spherical shape (Cadart et al, 2014; Lancaster et al, 2013; Maddox and Burridge, 2003; Ramanathan et al, 2015; Son et al, 2015; Stewart et al, 2011). Cells adopt at mitosis a spherical shape (Cadart et al, 2014; Lancaster et al, 2013; Maddox and Burridge, 2003; Ramanathan et al, 2015; Son et al, 2015; Stewart et al, 2011) This mitotic cell rounding is important for the efficient formation of a bipolar spindle and organization of a metaphase plate (Champion et al, 2017; Lancaster et al, 2013).
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