title: Identification and localization of the sperm CRISP family protein CiUrabin involved in gamete interaction in the ascidian Ciona intestinalis.
abstract: Ascidians are hermaphrodites, and most release sperm and eggs nearly simultaneously. Many species, including Halocynthia roretzi and Ciona intestinalis, are self-sterile. We previously reported that the interaction between a 12 EGF-like repeat-containing vitelline-coat (VC) protein, HrVC70, and a sperm GPI-anchored CRISP, HrUrabin, in lipid rafts plays a key role in self-/nonself-recognizable gamete interaction in H. roretzi. On the other hand, we recently identified two pairs of polymorphic genes responsible for self-incompatibility in C. intestinalis by positional cloning: The sperm polycystin 1-like receptors s-Themis-A/B and its fibrinogen-like ligand v-Themis-A/B on the VC. However, it is not known if the orthologs of HrVC70 and HrUrabin also participate in gamete interaction in C. intestinalis since they are from different orders. Here, we tested for a C. intestinalis ortholog (CiUrabin) of HrUrabin by searching the genome database and proteomes of sperm lipid rafts. The identified CiUrabin belongs to the CRISP family, with a PR domain and a GPI-anchor-attachment site. CiUrabin appears to be specifically expressed in the testis and localized at the surface of the sperm head, as revealed by Northern blotting and immunocytochemistry, respectively. The specific interaction between CiVC57, a C. intestinalis ortholog of HrVC70, and CiUrabin was confirmed by Far Western analysis, similarly to the interaction between HrVC70 and HrUrabin. The molecular interaction between CiVC57 and CiUrabin may be involved in the primary binding of sperm to the VC prior to the allorecognition process, mediated by v-Themis-A/B and s-Themis-A/B, during fertilization of C. intestinalis.
authors.affiliation: Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Sugashima, Toba, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Takako
authors.initials: T
authors.lastname: Saito
authors.forename: Lixy
authors.initials: L
authors.lastname: Yamada
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Harada
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sawada
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002938:Ciona intestinalis / Q000235:genetics / Q000378:metabolism*; D004527:Egg Proteins / Q000378:metabolism; D005306:Fertilization; D057850:Hermaphroditic Organisms / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D016415:Sequence Alignment; D013094:Spermatozoa / Q000737:chemistry*; D013737:Testis / Q000737:chemistry / Q000378:metabolism; D014461:Ultracentrifugation; D014817:Vitelline Membrane / Q000378:metabolism
chemical_list: D004527:Egg Proteins; D008562:Membrane Glycoproteins