Publications by authors named "Asako Sugimoto"

41 Publications

Two phases of astral microtubule activity during cytokinesis in C. elegans embryos.

Dev Cell 2006 Apr;10(4):509-20

Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Kobe, 650-0047, Japan.

Microtubules of the mitotic spindle are believed to provide positional cues for the assembly of the actin-based contractile ring and the formation of the subsequent cleavage furrow during cytokinesis. In Caenorhabditis elegans, astral microtubules have been thought to inhibit cortical contraction outside the cleavage furrow. Here, we demonstrate by live imaging and RNA interference (RNAi) that astral microtubules play two distinct roles in initiating cleavage furrow formation. In early anaphase, microtubules are required for contractile ring assembly; in late anaphase, microtubules show different cortical behavior and seem to suppress cortical contraction at the poles, as suggested in previous studies. These two distinct phases of microtubule behavior depend on distinct regulatory pathways, one involving the gamma-tubulin complex and the other requiring aurora-A kinase. We propose that temporal and spatial regulation of two distinct phases of astral microtubule behavior is crucial in specifying the position and timing of furrowing.
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http://dx.doi.org/10.1016/j.devcel.2006.03.001DOI Listing
April 2006

[Genome-wide analyses of gene expression and function in C. elegans].

Tanpakushitsu Kakusan Koso 2005 Dec;50(16 Suppl):2140-5

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December 2005

The C. elegans eyes absent ortholog EYA-1 is required for tissue differentiation and plays partially redundant roles with PAX-6.

Dev Biol 2005 Oct 9;286(2):452-63. Epub 2005 Sep 9.

Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan.

eyes absent/Eya is a conserved transcriptional coactivator involved in development of various tissues and organs in arthropods and vertebrates. In Drosophila eye development, eya functions as part of the transcriptional regulatory network along with eyeless/Pax6, sine oculis/Six and dachshund/Dach. Here, we present the first functional study of the C. elegans Eya homolog, EYA-1. Loss of EYA-1 function by RNAi and deletion mutations resulted in early larval lethality with incomplete penetrance, associated with defects of differentiation and morphogenesis of several tissues and organs. In late embryogenesis, morphological defect in the head region, pharyngeal malformation and excess cell deaths in the anterior region were observed. Consistently, EYA-1 was expressed in the nuclei of a subset of anterior cells including pharyngeal and body wall muscle cells, starting from the morphogenesis stage in embryogenesis. Interestingly, eya-1 and pax-6/Pax6 mutants showed a strong genetic interaction for larval viability and embryonic anterior morphogenesis. Thus, eya-1 appears to play a partially redundant role with pax-6 during C. elegans embryogenesis.
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http://dx.doi.org/10.1016/j.ydbio.2005.08.011DOI Listing
October 2005

Caenorhabditis elegans geminin homologue participates in cell cycle regulation and germ line development.

J Biol Chem 2005 May 4;280(20):19689-94. Epub 2005 Apr 4.

Cellular Physiology Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama, Japan.

Cdt1 is an essential component for the assembly of a pre-replicative complex. Cdt1 activity is inhibited by geminin, which also participates in neural development and embryonic differentiation in many eukaryotes. Although Cdt1 homologues have been identified in organisms ranging from yeast to human, geminin homologues had not been described for Caenorhabditis elegans and fungi. Here, we identify the C. elegans geminin, GMN-1. Biochemical analysis reveals that GMN-1 associates with C. elegans CDT-1, the Hox protein NOB-1, and the Six protein CEH-32. GMN-1 inhibits not only the interaction between mouse Cdt1 and Mcm6 but also licensing activity in Xenopus egg extracts. RNA interference-mediated reduction of GMN-1 is associated with enlarged germ nuclei with aberrant nucleolar morphology, severely impaired gametogenesis, and chromosome bridging in intestinal cells. We conclude that the Cdt1-geminin system is conserved throughout metazoans and that geminin has evolved in these taxa to regulate proliferation and differentiation by directly interacting with Cdt1 and homeobox proteins.
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http://dx.doi.org/10.1074/jbc.C500070200DOI Listing
May 2005

Caenorhabditis elegans DAZ-1 is expressed in proliferating germ cells and directs proper nuclear organization and cytoplasmic core formation during oogenesis.

Dev Biol 2005 Jan;277(1):142-54

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo, 113-0032 Japan.

The deleted in azoospermia (DAZ) family genes encode potential RNA-binding proteins that are expressed exclusively in germ cells in a wide range of metazoans. We have previously shown that mutations in daz-1, the only DAZ family gene in Caenorhabditis elegans, cause pachytene stage arrest of female germ cells but do not affect spermatogenesis. In this study, we report that DAZ-1 protein is most abundantly expressed in proliferating female germ cells, in a manner independent of the GLP-1 signaling pathway. DAZ-1 is dispensable in males but it is expressed also in male mitotic germ cells. Detailed phenotypic analyses with fluorescence microscopy and transmission electron microscopy have revealed that loss of daz-1 function causes multiple abnormalities as early as the onset of meiotic prophase, which include aberrant chromatin structure, small nucleoli, absence of the cytoplasmic core, and precocious cellularization. Although the reduced size of nucleoli is indicative of a low translational activity in these cells, artificial repression of general translation in the germline does not phenocopy the daz-1 mutant. Thus, we propose that DAZ-1 in C. elegans plays essential roles in female premeiotic and early meiotic germ cells, probably via regulating the translational activity of specific target genes required for the progression of oogenesis.
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http://dx.doi.org/10.1016/j.ydbio.2004.08.053DOI Listing
January 2005

Type II platelet-activating factor-acetylhydrolase is essential for epithelial morphogenesis in Caenorhabditis elegans.

Proc Natl Acad Sci U S A 2004 Sep 30;101(36):13233-8. Epub 2004 Aug 30.

Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Type II platelet-activating factor-acetylhydrolase [PAF-AH (II)] is an N-myristoylated enzyme that contains a lipase/esterase catalytic motif and selectively hydrolyzes the sn-2 acetyl ester of PAF and other short-chain acyl groups attached to phosphoglycerides. However, the physiological role of this enzyme remains to be elucidated. PAF-AH (II) is conserved in a variety of species ranging from a simple multicellular organism, Caenorhabditis elegans, to mammals. C. elegans possesses two homologous PAF-AH (II) genes, named paf-1 and paf-2. In this study, we generated these two loss-of-function mutants to elucidate the in vivo PAF-AH (II) function. Surprisingly, mutants of paf-2, a major isoform of C. elegans PAF-AH (II)s, exhibits gross defects in epithelial sheet formation, resulting in unsuccessful subsequent morphogenesis with complete penetrance. Moreover, paf-2 RNA interference worms show a variable abnormal morphology, including ectopic protrusions and a lumpy shape at the late embryonic and early larval stages due to epithelial organization defects. Consistent with these phenotypes, PAF-AH (II) is predominantly expressed in epithelial cells of C. elegans. This study demonstrates that PAF-AH (II) is essential for epithelial morphogenesis.
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http://dx.doi.org/10.1073/pnas.0405507101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC516553PMC
September 2004

High-throughput RNAi in Caenorhabditis elegans: genome-wide screens and functional genomics.

Authors:
Asako Sugimoto

Differentiation 2004 Mar;72(2-3):81-91

Laboratory for Developmental Genomics, RIKEN Center for Developmental Biology, 2-2-3, Minatojima-Minamimachi, Chuo-ku, Kobe, 650-0047, Japan.

The phenomenon of RNA-mediated interference (RNAi) was first discovered in the nematode Caenorhabditis elegans, in which introduction of double-stranded RNA causes specific inactivation of genes with corresponding sequences. Technical advances in RNAi methodology and the availability of the complete genome sequence have enabled the high-throughput, genome-wide RNAi analysis of this organism. Several groups have used large-scale RNAi to systematically examine every C. elegans gene for knock-down phenotypes, providing basal information to be mined in more detailed studies. Now, in addition to functional genomic RNAi analyses, high-throughput RNAi is also routinely used for rapid, genome-wide screens for genes involved in specific biological processes. The integration of high-throughput RNAi experiments with other large-scale data, such as DNA microarrays and protein-protein interaction maps, enhances the speed and reliability of such screens. The accumulation of RNAi phenotype data dramatically accelerates our understanding of this organism at the genetic level.
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http://dx.doi.org/10.1111/j.1432-0436.2004.07202004.xDOI Listing
March 2004

Distinct developmental function of two Caenorhabditis elegans homologs of the cohesin subunit Scc1/Rad21.

Mol Biol Cell 2003 Jun 6;14(6):2399-409. Epub 2003 Feb 6.

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Japan.

Cohesin, which mediates sister chromatid cohesion, is composed of four subunits, named Scc1/Rad21, Scc3, Smc1, and Smc3 in yeast. Caenorhabditis elegans has a single homolog for each of Scc3, Smc1, and Smc3, but as many as four for Scc1/Rad21 (COH-1, SCC-1/COH-2, COH-3, and REC-8). Except for REC-8 required for meiosis, function of these C. elegans proteins remains largely unknown. Herein, we examined their possible involvement in mitosis and development. Embryos depleted of the homolog of either Scc3, or Smc1, or Smc3 by RNA interference revealed a defect in mitotic chromosome segregation but not in chromosome condensation and cytokinesis. Depletion of SCC-1/COH-2 caused similar phenotypes. SCC-1/COH-2 was present in cells destined to divide. It localized to chromosomes in a cell cycle-dependent manner. Worms depleted of COH-1 arrested at either the late embryonic or the larval stage, with no indication of mitotic dysfunction. COH-1 associated chromosomes throughout the cell cycle in all somatic cells undergoing late embryogenesis or larval development. Thus, SCC-1/COH-2 and the homologs of Scc3, Smc1, and Smc3 facilitate mitotic chromosome segregation during the development, presumably by forming a cohesin complex, whereas COH-1 seems to play a role important for development but unrelated to mitosis.
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http://dx.doi.org/10.1091/mbc.e02-09-0603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC194888PMC
June 2003

Essential role of the C. elegans Arp2/3 complex in cell migration during ventral enclosure.

J Cell Sci 2003 Apr;116(Pt 8):1505-18

Department of Biochemistry, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.

Migration of cells through the reorganization of the actin cytoskeleton is essential for morphogenesis of multicellular animals. In a cell culture system, the actin-related protein (Arp) 2/3 complex functions as a nucleation core for actin polymerization when activated by the members of the WASP (Wiskott-Aldrich syndrome protein) family. However, the regulation of cell motility in vivo remains poorly understood. Here we report that homologues of the mammalian Arp2/3 complex and N-WASP in Caenorhabditis elegans play an important role in hypodermal cell migration during morphogenesis, a process known as ventral enclosure. In the absence of one of any of the C. elegans Arp2/3 complex subunits (ARX-1, ARX-2, ARX-4, ARX-5, ARX-6 or ARX-7) or of N-WASP (WSP-1), hypodermal cell migration led by actin-rich filopodia formation is inhibited during ventral enclosure owing to the reduction of filamentous actin formation. However, there is no effect on differentiation of hypodermal cells and dorsal intercalation. Disruption of the function of ARX-1 and WSP-1 in hypodermal cells also resulted in hypodermal cell arrest during ventral enclosure, suggesting that their function is cell autonomous. WSP-1 protein activated Arp2/3-mediated actin polymerization in vitro. Consistent with these results, the Arp2/3 complex and WSP-1 colocalized at the leading edge of migrating hypodermal cells. The stable localization of WSP-1 was dependent on the presence of Arp2/3 complex, suggesting an interaction between the Arp2/3 complex and WSP-1 in vivo.
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http://dx.doi.org/10.1242/jcs.00362DOI Listing
April 2003

Protein phosphatase 4 is required for centrosome maturation in mitosis and sperm meiosis in C. elegans.

J Cell Sci 2002 Apr;115(Pt 7):1403-10

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.

The centrosome consists of two centrioles surrounded by the pericentriolar material (PCM). In late G2 phase, centrosomes enlarge by recruiting extra PCM, and concomitantly its microtubule nucleation activity increases dramatically. The regulatory mechanisms of this dynamic change of centrosomes are not well understood. Protein phosphatase 4 (PP4) is known to localize to mitotic centrosomes in mammals and Drosophila. An involvement of PP4 in the mitotic spindle assembly has been implicated in Drosophila, but in vivo functions of PP4 in other organisms are largely unknown. Here we characterize two Caenorhabditis elegans PP4 genes, named pph-4.1 and pph-4.2. Inhibition of the function of each gene by RNA-mediated interference (RNAi) revealed that PPH-4.1 was essential for embryogenesis but PPH-4.2 was not. More specifically, PPH-4.1 was required for the formation of spindles in mitosis and sperm meiosis. However, this phosphatase was apparently dispensable for female meiotic divisions, which do not depend on centrosomes. In the cell depleted of pph-4.1 activity, localization of gamma-tubulin and a Polo-like kinase homologue to the centrosome was severely disturbed. Immunofluorescence staining revealed that PPH-4.1 was present at centrosomes from prophase to telophase, but not during interphase. These results indicate that PPH-4.1 is a centrosomal protein involved in the recruitment of PCM components to the centrosome, and is essential for the activation of microtubule nucleation potential of the centrosome. Furthermore, chiasmata between homologous chromosomes were often absent in oocytes that lacked pph-4.1 activity. Thus, besides promoting spindle formation, PPH-4.1 appears to play a role in either the establishment or the maintenance of chiasmata during meiotic prophase I.
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April 2002

The stem-loop binding protein CDL-1 is required for chromosome condensation, progression of cell death and morphogenesis in Caenorhabditis elegans.

Development 2002 Jan;129(1):187-96

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo, 113-0032, Japan.

Histones play important roles not only in the structural changes of chromatin but also in regulating gene expression. Expression of histones is partly regulated post-transcriptionally by the stem-loop binding protein (SLBP)/hairpin binding protein (HBP). We report the developmental function of CDL-1, the C. elegans homologue of SLBP/HBP. In the C. elegans cdl-1 mutants, cell corpses resulting from programmed cell death appear later and persist much longer than those in the wild type. They also exhibit distinct morphological defects in body elongation and movement of the pharyngeal cells toward the buccal opening. The CDL-1 protein binds to the stem-loop structures in the 3'-UTR of C. elegans core histone mRNAs, and the mutant forms of this protein show reduced binding activities. A decrease in the amount of core histone proteins phenocopied the cdl-1 mutant embryos, suggesting that CDL-1 contributes to the proper expression of core histone proteins. We propose that loss-of-function of cdl-1 causes aberrant chromatin structure, which affects the cell cycle and cell death, as well as transcription of genes essential for morphogenesis.
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January 2002