title: The Immunoglobulin-like Gene spe-45 Acts during Fertilization in Caenorhabditis elegans like the Mouse Izumo1 Gene.
abstract: The Caenorhabditis elegans spe-9 class genes, which show specific or predominant expression in the male germline, are indispensable for fertilization [1, 2]. However, due to the rapid evolution of genes involved in reproduction, we do not currently know if there are spe-9 class genes in mammals that play similar roles during fertilization to those found in C. elegans. In mice, the Izumo1 gene encodes a sperm-specific transmembrane (TM) protein with a single immunoglobulin (Ig)-like domain that is absolutely required for gamete fusion [3, 4]. In this study, we hypothesized that C. elegans has a new member of the spe-9 class genes coding for an IZUMO1-like protein. We screened C. elegans microarray data [5, 6] to identify male germline-enriched genes that encode membrane proteins with Ig-like domains. A deletion (tm3715) in one such gene (F28D1.8) caused hermaphrodites to show a male germline-dependent self-sterility, so we have named it spe-45. Mutant spe-45 worms seemed to normally undergo spermatogenesis (spermatid production by meiosis) and spermiogenesis (spermatid activation into actively motile spermatozoa). spe-45 mutant spermatozoa, however, could not complete gamete fusion, which is a characteristic of all spe-9 class mutants [1, 2]. Moreover, spe-45 self-sterile worms were rescued by a transgene expressing chimeric SPE-45 protein in which its Ig-like domain was replaced by the Ig-like domain from mouse IZUMO1. Hence, C. elegans SPE-45 and mouse IZUMO1 appear to have retained a common function(s) that is required during fertilization.
authors.affiliation: Department of Life Science, Setsunan University, Neyagawa, Osaka 572-8508, Japan; Department of Biology, Emory University, Atlanta, GA 30322, USA. Electronic address: nishimura@lif.setsunan.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nishimura
authors.affiliation: Department of Life Science, Setsunan University, Neyagawa, Osaka 572-8508, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tajima
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Heather Skye
authors.initials: HS
authors.lastname: Comstra
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Gleason
authors.affiliation: Department of Biology, Emory University, Atlanta, GA 30322, USA. Electronic address: bioslh@emory.edu.
authors.forename: Steven W
authors.initials: SW
authors.lastname: L'Hernault
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D005260:Female; D005306:Fertilization; D007136:Immunoglobulins / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D013091:Spermatogenesis
chemical_list: D029742:Caenorhabditis elegans Proteins; D007136:Immunoglobulins; C498177:Izumo1 protein, mouse; D008565:Membrane Proteins; C000611169:spe-45 protein, C elegans