title: RhoGEF and positioning of rappaport-like furrows in the early Drosophila embryo.
abstract: Early Drosophila embryogenesis is characterized by shifting from astral microtubule-based to central spindle-based positioning of cleavage furrows. Before cellularization, astral microtubules determine metaphase furrow position by producing Rappaport-like furrows, which encompass rather than bisect the spindle. Their positioning is explained by our finding that the conserved central spindle components centralspindlin (mKLP1 and RacGAP50C), Polo, and Fascetto (Prc1) localize to the astral microtubule overlap region. These components and the chromosomal passenger complex localize to the central spindle, though no furrow forms there. We identify the maternally supplied RhoGEF2 as a key factor in metaphase furrow positioning. Unlike the zygotic, central spindle-localized RhoGEF (Pebble), RhoGEF2 localizes to metaphase furrows, a function distinct from RhoGEF/Pebble and likely due to the absence of a RacGAP50C binding domain. Accordingly, we find that ectopic activation of Rho GTPase generates furrows perpendicular to the central spindle during syncytial divisions. Whereas metaphase furrow formation is myosin independent, these ectopic furrows, like conventional furrows, require myosin as well as microtubules. These studies demonstrate that early Drosophila embryogenesis is primed to form furrows at either overlapping astral microtubules or the central spindle. We propose that the shift to the latter is driven by a corresponding shift from RhoGEF2 to Pebble in controlling furrow formation.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Sinsheimer Laboratories, University of California, Santa Cruz, Santa Cruz, CA 95064, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Crest
authors.forename: Kirsten
authors.initials: K
authors.lastname: Concha-Moore
authors.forename: William
authors.initials: W
authors.lastname: Sullivan
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002970:Cleavage Stage, Ovum / Q000378:metabolism*; D004330:Drosophila / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism* / Q000648:ultrastructure; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D008677:Metaphase / Q000502:physiology; D008870:Microtubules / Q000502:physiology / Q000648:ultrastructure; D008938:Mitosis; D064067:Rho Guanine Nucleotide Exchange Factors; D008941:Spindle Apparatus / Q000502:physiology / Q000648:ultrastructure; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; C121865:Pbl protein, Drosophila; D064067:Rho Guanine Nucleotide Exchange Factors; C465504:sav protein, Drosophila; D020741:rho GTP-Binding Proteins