The Egg Surface LDL Receptor Repeat-Containing Proteins EGG-1 and EGG-2 Are Required for Fertilization in Caenorhabditis elegans

• DOI: 10.1016/j.cub.2005.10.043
• Publication Date: 2005-12-20T15:21:35Z
• Authors: Pavan Kadandale; Allison Stewart-M...; Scott Gordon; Jacob Rubin; Richard Klancer; Peter Schweinsberg; Barth D. Grant; Andrew Singson
• Keywords: Male; Sperm-Ovum Interactions; 0303 health sciences; Agricultural and Biological Sciences(all); Biochemistry, Genetics and Molecular Biology(all); Green Fluorescent Proteins; Computational Biology; Receptors, Cell Surface; Sequence Analysis, DNA; Animals, Genetically Modified; 03 medical and health sciences; Receptors, LDL; Fertilization; Animals; Cluster Analysis; Female; RNA Interference; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Phylogeny; Ovum

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.