title: Nucleologenesis in the Caenorhabditis elegans embryo.
abstract: In the Caenorhabditis elegans nematode, the oocyte nucleolus disappears prior to fertilization. We have now investigated the re-formation of the nucleolus in the early embryo of this model organism by immunostaining for fibrillarin and DAO-5, a putative NOLC1/Nopp140 homolog involved in ribosome assembly. We find that labeled nucleoli first appear in somatic cells at around the 8-cell stage, at a time when transcription of the embryonic genome begins. Quantitative analysis of radial positioning showed the nucleolus to be localized at the nuclear periphery in a majority of early embryonic nuclei. At the ultrastructural level, the embryonic nucleolus appears to be composed of a relatively homogenous core surrounded by a crescent-shaped granular structure. Prior to embryonic genome activation, fibrillarin and DAO-5 staining is seen in numerous small nucleoplasmic foci. This staining pattern persists in the germline up to the ∼100-cell stage, until the P4 germ cell divides to give rise to the Z2/Z3 primordial germ cells and embryonic transcription is activated in this lineage. In the ncl-1 mutant, which is characterized by increased transcription of rDNA, DAO-5-labeled nucleoli are already present at the 2-cell stage. Our results suggest a link between the activation of transcription and the initial formation of nucleoli in the C. elegans embryo.
authors: Institute of Cellular Biology and Pathology, First Faculty of Medicine, Charles University, Prague, Czech Republic.
authors: Darina
authors: D
authors: Korčeková
authors: Adriána
authors: A
authors: Gombitová
authors: Ivan
authors: I
authors: Raška
authors: Dušan
authors: D
authors: Cmarko
authors: Christian
authors: C
authors: Lanctôt
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004625:Embryo, Nonmammalian / Q000196:embryology* / Q000648:ultrastructure; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D049751:Genome, Helminth / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D009687:Nuclear Proteins