Single-molecule dynamics of the P granule scaffold MEG-3 in the Caenorhabditis elegans zygote

Mol Biol Cell. 2019 Feb 1;30(3):333-345. doi: 10.1091/mbc.E18-06-0402. Epub 2018 Dec 12.


During the asymmetric division of the Caenorhabditis elegans zygote, germ (P) granules are disassembled in the anterior cytoplasm and stabilized/assembled in the posterior cytoplasm, leading to their inheritance by the germline daughter cell. P granule segregation depends on MEG (maternal-effect germline defective)-3 and MEG-4, which are enriched in P granules and in the posterior cytoplasm surrounding P granules. Here we use single-molecule imaging and tracking to characterize the reaction/diffusion mechanisms that result in MEG-3::Halo segregation. We find that the anteriorly enriched RNA-binding proteins MEX (muscle excess)-5 and MEX-6 suppress the retention of MEG-3 in the anterior cytoplasm, leading to MEG-3 enrichment in the posterior. We provide evidence that MEX-5/6 may work in conjunction with PLK-1 kinase to suppress MEG-3 retention in the anterior. Surprisingly, we find that the retention of MEG-3::Halo in the posterior cytoplasm surrounding P granules does not appear to contribute significantly to the maintenance of P granule asymmetry. Rather, our findings suggest that the formation of the MEG-3 concentration gradient and the segregation of P granules are two parallel manifestations of MEG-3's response to upstream polarity cues.

Publication types

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

MeSH terms

  • Animals
  • Caenorhabditis elegans / embryology*
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / metabolism*
  • Cytoplasmic Granules / metabolism*
  • Embryo, Nonmammalian / metabolism
  • Green Fluorescent Proteins / metabolism
  • Protein Multimerization
  • Single Molecule Imaging*
  • Zygote / metabolism*


  • Caenorhabditis elegans Proteins
  • MEG-3 protein, C elegans
  • MEX-5 protein, C elegans
  • Green Fluorescent Proteins