Control of nuclear centration in the C. elegans zygote by receptor-independent Galpha signaling and myosin II.
Mitotic spindle positioning in the Caenorhabditis elegans zygote involves microtubule-dependent pulling forces applied to centrosomes. In this study, we investigate the role of actomyosin in centration, the movement of the nucleus-centrosome complex (NCC) to the cell center. We find that the rate of wild-type centration depends equally on the nonmuscle myosin II NMY-2 and the Galpha proteins GOA-1/GPA-16. In centration- defective let-99(-) mutant zygotes, GOA-1/GPA-16 and NMY-2 act abnormally to oppose centration. This suggests that LET-99 determines the direction of a force on the NCC that is promoted by Galpha signaling and actomyosin. During wild-type centration, NMY-2-GFP aggregates anterior to the NCC tend to move further anterior, suggesting that actomyosin contraction could pull the NCC. In GOA-1/GPA-16-depleted zygotes, NMY-2 aggregate displacement is reduced and largely randomized, whereas in a let-99(-) mutant, NMY-2 aggregates tend to make large posterior displacements. These results suggest that Galpha signaling and LET-99 control centration by regulating polarized actomyosin contraction.
Goulding
Morgan B
MB
Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA. goulding@uoregon.edu
Canman
Julie C
JC
Senning
Eric N
EN
Marcus
Andrew H
AH
Bowerman
Bruce
B
D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D016764:Cell Polarity; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008938:Mitosis; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D015053:Zygote / Q000166:cytology / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; C516620:GOA-1 protein, C elegans; D044385:GTP-Binding Protein alpha Subunits; C467518:LET-99 protein, C elegans; C480837:NMY-2 protein, C elegans; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000205:Actomyosin; D019204:GTP-Binding Proteins; D024462:Myosin Type II; D018995:Myosin Heavy Chains; C480838:GPA-16 protein, C elegans; D019206:GTP-Binding Protein alpha Subunits, Gi-Go