P granules in the germ cells of Caenorhabditis elegans adults are associated with clusters of nuclear pores and contain RNA

Dev Biol. 2000 Mar 15;219(2):315-33. doi: 10.1006/dbio.2000.9607.


The germ cells, and germ cell precursors, in the nematode Caenorhabditis elegans contain distinctive granules called P granules. During early embryogenesis, P granules are segregated asymmetrically into those blastomeres that eventually produce the germ line. Because of the correlation between P granule distribution and the development of the germ line, P granules are widely thought to function in some aspect of germ line specification or differentiation. Most of the analysis of P granule structure and localization has focused on the early embryo, when P granules are located in the cytoplasm. However, during most of development P granules are associated with germ cell nuclei. We report here an ultrastructural analysis of the nuclear-associated P granules in the germ cells of the adult hermaphrodite gonad. We show that P granules are tightly associated with nuclear pores and that the positions of certain structures within the P granules correspond to the positions of pores on the nuclear envelope. We present immunocytochemical and ultrastructural data suggesting that P granules can associate, or remain associated, with pore-like structures even after they detach from the nuclear envelope during oogenesis. Finally, we show that nuclear-associated P granules in the gonad contain RNA, complementing previous studies showing that cytoplasmic P granules in embryos contain RNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans / ultrastructure*
  • Cytoplasmic Granules / metabolism
  • Cytoplasmic Granules / ultrastructure
  • DNA Probes / genetics
  • Female
  • Germ Cells / metabolism*
  • Germ Cells / ultrastructure*
  • In Situ Hybridization
  • Male
  • Microscopy, Electron
  • Nuclear Envelope / metabolism
  • Nuclear Envelope / ultrastructure
  • RNA Splicing
  • RNA, Helminth / genetics
  • RNA, Helminth / metabolism*


  • DNA Probes
  • RNA, Helminth