title: LET-99 inhibits lateral posterior pulling forces during asymmetric spindle elongation in C. elegans embryos.
abstract: Cortical pulling on astral microtubules positions the mitotic spindle in response to PAR polarity cues and G protein signaling in many systems. In Caenorhabditis elegans single-cell embryos, posterior spindle displacement depends on Galpha and its regulators GPR-1/2 and LIN-5. GPR-1/2 and LIN-5 are necessary for cortical pulling forces and become enriched at the posterior cortex, which suggests that higher forces act on the posterior spindle pole compared with the anterior pole. However, the precise distribution of cortical forces and how they are regulated remains to be determined. Using spindle severing, single centrosome assays, and centrosome fragmentation, we show that both the anterior and posterior cortices generate more pulling force than the lateral-posterior region. Lateral inhibition depends on LET-99, which inhibits GPR-1/2 localization to produce a bipolar GPR-1/2 pattern. Thus, rather than two domains of cortical force, there are three. We propose that the attenuation of lateral forces prevents counterproductive pulling, resulting in a higher net force toward the posterior that contributes to spindle elongation and displacement.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA.
authors.forename: Lori E
authors.initials: LE
authors.lastname: Krueger
authors.forename: Jui-Ching
authors.initials: JC
authors.lastname: Wu
authors.forename: Meng-Fu Bryan
authors.initials: MF
authors.lastname: Tsou
authors.forename: Lesilee S
authors.initials: LS
authors.lastname: Rose
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology; D008941:Spindle Apparatus / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C475458:G protein regulator 1, C elegans; C475459:G protein regulator 2, C elegans; C467518:LET-99 protein, C elegans; C404808:lin-5 protein, C elegans