The egg surface LDL receptor repeat-containing proteins EGG-1 and EGG-2 are required for fertilization in Caenorhabditis elegans.
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.
Kadandale
Pavan
P
Waksman Institute and Department of Genetics, Rutgers University, Piscataway, New Jersey 08854, USA.
Stewart-Michaelis
Allison
A
Gordon
Scott
S
Rubin
Jacob
J
Klancer
Richard
R
Schweinsberg
Peter
P
Grant
Barth D
BD
Singson
Andrew
A
D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D016000:Cluster Analysis; D019295:Computational Biology; D005260:Female; D005306:Fertilization / Q000502:physiology*; D049452:Green Fluorescent Proteins; D008297:Male; D010063:Ovum / Q000378:metabolism*; D010802:Phylogeny; D034622:RNA Interference; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011973:Receptors, LDL / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013084:Sperm-Ovum Interactions / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; C514294:EGG-1 protein, C elegans; C514295:EGG-2 protein, C elegans; D011956:Receptors, Cell Surface; D011973:Receptors, LDL; D049452:Green Fluorescent Proteins