Nucleoporins NPP-1, NPP-3, NPP-4, NPP-11 and NPP-13 are required for proper spindle orientation in C. elegans.
Nucleoporins are components of the nuclear pore, which is required for nucleo-cytoplasmic transport. We report a role for a subclass of nucleoporins in orienting the mitotic spindle in C. elegans embryos. RNAi-mediated depletion of any of five putative nucleoporins npp-1, npp-3, npp-4, npp-11, and npp-13 leads to indistinguishable spindle orientation defects. Transgenic worms expressing NPP-1::GFP or NPP-11::GFP show GFP localization at the nuclear envelope, consistent with their predicted function. NPP-1 interacts with the other nucleoporins in yeast two-hybrid assays, suggesting that the proteins affect spindle orientation by a common process. The failed orientation phenotype of npp-1(RNAi) is at least partially epistatic to the ectopic spindle rotation in the AB blastomere of par-3 mutant embryos. This suggests that NPP-1 contributes to the mechanics of spindle orientation. However, NPP-1 is also required for PAR-6 asymmetry at the two-cell stage, indicating that nucleoporins may be required to define cortical domains in the germ line blastomere P1. Nuclear envelope structure is abnormal in npp-1(RNAi) embryos, but the envelope maintains its integrity, and most nuclear proteins we assayed accumulate normally. These findings raise the possibility that these nucleoporins may have direct roles in orienting the mitotic spindle and the maintenance of cell polarity.
Schetter
Aaron
A
Department of Molecular Biology and Genetics, Cornell University, 435 Biotechnology Building, Ithaca, NY 14853, USA.
Askjaer
Peter
P
Piano
Fabio
F
Mattaj
Iain
I
Kemphues
Kenneth
K
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division; D004274:DNA, Recombinant / Q000378:metabolism; D000072159:Dynactin Complex; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008957:Models, Genetic; D009685:Nuclear Envelope / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000235:genetics* / Q000502:physiology; D034622:RNA Interference; D008941:Spindle Apparatus / Q000502:physiology*; D020798:Two-Hybrid System Techniques
D029742:Caenorhabditis elegans Proteins; D004274:DNA, Recombinant; D000072159:Dynactin Complex; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; C577012:NPP-3 protein, C elegans; D028861:Nuclear Pore Complex Proteins; C410544:ooc-3 protein, C elegans; D000251:Adenosine Triphosphatases; C442329:OOC-5 protein, C elegans