LET-99, GOA-1/GPA-16, and GPR-1/2 Are Required for Aster-Positioned Cytokinesis

• DOI: 10.1016/j.cub.2006.11.070
• Publication Date: 2006-12-29T12:11:20Z
• Authors: Henrik Bringmann; Carrie R. Cowan; Jun Kong; Anthony A. Hyman
• Keywords: 0301 basic medicine; Embryo, Nonmammalian; Time Factors; Agricultural and Biological Sciences(all); Biochemistry, Genetics and Molecular Biology(all); Spindle Apparatus; GTP-Binding Protein alpha Subunits, Gi-Go; Heterotrimeric GTP-Binding Proteins; GTP-Binding Protein alpha Subunits; 03 medical and health sciences; GTP-Binding Proteins; Animals; CELLBIO; RNA Interference; Anaphase; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Cytokinesis

At anaphase, the mitotic spindle positions the cytokinesis furrow [1]. Two populations of spindle microtubules are implicated in cytokinesis: radial microtubule arrays called asters and bundled nonkinetochore microtubules called the spindle midzone [2-4]. In C. elegans embryos, these two populations of microtubules provide two consecutive signals that position the cytokinesis furrow: The first signal is positioned midway between the microtubule asters; the second signal is positioned over the spindle midzone [5]. Evidence for two cytokinesis signals came from the identification of molecules that block midzone-positioned cytokinesis [5-7]. However, no molecules that are only required for, and thus define, the molecular pathway of aster-positioned cytokinesis have been identified. With RNAi screening, we identify LET-99 and the heterotrimeric G proteins GOA-1/GPA-16 and their regulator GPR-1/2 [10-12] in aster-positioned cytokinesis. By using mechanical spindle displacement, we show that the anaphase spindle positions cortical LET-99, at the site of the presumptive cytokinesis furrow. LET-99 enrichment at the furrow depends on the G proteins. GPR-1 is locally reduced at the site of cytokinesis-furrow formation by LET-99, which prevents accumulation of GPR-1 at this site. We conclude that LET-99 and the G proteins define a molecular pathway required for aster-positioned cytokinesis.