The egg surface LDL receptor repeat-containing proteins EGG-1 and EGG-2 are required for fertilization in Caenorhabditis elegans

Curr Biol. 2005 Dec 20;15(24):2222-9. doi: 10.1016/j.cub.2005.10.043.

Abstract

The molecular machinery that mediates sperm-egg interactions at fertilization is largely unknown. We identify two partially redundant egg surface LDL receptor repeat-containing proteins (EGG-1 and EGG-2) that are required for Caenorhabditis elegans fertility in hermaphrodites, but not males. Wild-type sperm cannot enter the morphologically normal oocytes produced by hermaphrodites that lack egg-1 and egg-2 function despite direct gamete contact. Furthermore, we find that levels of meiotic maturation/ovulation and sperm migratory behavior are altered in egg-1 mutants. These observations suggest an unexpected regulatory link between fertilization and other events necessary for reproductive success. egg-1 and egg-2 are the result of a gene duplication in the nematode lineage leading to C. elegans. The two closely related species C. briggsae and C. remanei encode only a single egg-1/egg-2 homolog that is required for hermaphrodite/female fertility. In addition to being the first identified egg components of the nematode fertilization machinery, the egg-1 and egg-2 gene duplication could be vital with regards to maximizing C. elegans fecundity and understanding the evolutionary differentiation of molecular function and speciation.

Publication types

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

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Caenorhabditis elegans / physiology*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Cluster Analysis
  • Computational Biology
  • Female
  • Fertilization / physiology*
  • Green Fluorescent Proteins
  • Male
  • Ovum / metabolism*
  • Phylogeny*
  • RNA Interference
  • Receptors, Cell Surface / metabolism*
  • Receptors, LDL / metabolism*
  • Sequence Analysis, DNA
  • Sperm-Ovum Interactions / physiology*

Substances

  • Caenorhabditis elegans Proteins
  • EGG-1 protein, C elegans
  • EGG-2 protein, C elegans
  • Receptors, Cell Surface
  • Receptors, LDL
  • Green Fluorescent Proteins