Self/nonself recognition in ascidian fertilization: vitelline coat protein HrVC70 is a candidate allorecognition molecule.

Ascidians are hermaphrodites releasing sperm and eggs simultaneously, but many species are self-sterile because of a self/nonself-recognition system in spermegg interaction. Here, we show that a 70-kDa vitelline coat protein, HrVC70, consisting of 12 epidermal growth factor-like repeats, plays a key role in self/nonself recognition during ascidian fertilization. We discovered that the amount of HrVC70 of the self-sterile mature oocytes is markedly higher than that of the self-fertile immature oocytes and that the selfsterile mature oocytes become self-fertile by acid treatment, which is able to release the HrVC70 from isolated vitelline coats. In addition, fertilization is strongly inhibited by the pretreatment of sperm with HrVC70 from a different individual, but not from the same individual, and the number of nonself sperm bound to HrVC70-agarose was significantly higher than that of self-sperm. A sequence analysis of HrVC70 disclosed that several amino acid residues in a restricted region are substituted at an individual level, with no identical sequences among the 10 individuals tested. Furthermore, genomic DNA analysis revealed that the epidermal growth factor-like domains correspond to the exons, and each intron is highly conserved among even- and odd-numbered introns, suggesting that multiple gene duplications or amplification of this region might have taken place during evolution. It was also found that diversity in cDNA sequences is derived from genomic DNA polymorphism probably elicited by crossing over and specific nucleotide substitutions. These results indicate that HrVC70 is a candidate allogeneic recognition molecule in the gamete interaction of the ascidian Halocynthia roretzi.

[1]  M. Ensslin,et al.  Identification of Mouse Sperm SED1, a Bimotif EGF Repeat and Discoidin-Domain Protein Involved in Sperm-Egg Binding , 2003, Cell.

[2]  Paul Richardson,et al.  The Draft Genome of Ciona intestinalis: Insights into Chordate and Vertebrate Origins , 2002, Science.

[3]  H. Yokosawa,et al.  Extracellular ubiquitination and proteasome-mediated degradation of the ascidian sperm receptor , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[4]  C. Lambert,et al.  Mechanism of the block to hybridization and selfing between the sympatric ascidians Ciona intestinalis and Ciona savignyi , 2000, Molecular reproduction and development.

[5]  T. Numakunai,et al.  Self‐sterility of eggs induced by exogenous and endogenous protease in the solitary ascidian, Halocynthia roretzi , 1999 .

[6]  S. L'Hernault,et al.  The C. elegans spe-9 Gene Encodes a Sperm Transmembrane Protein that Contains EGF-like Repeats and Is Required for Fertilization , 1998, Cell.

[7]  R. Santis,et al.  The hsp70 protein is involved in the acquisition of gamete self-sterility in the ascidian Ciona intestinalis. , 1998, Development.

[8]  M. Hanson,et al.  A guide to RNA editing. , 1997, RNA.

[9]  J. Weissenbach,et al.  Notch3 mutations in CADASIL, a hereditary adult-onset condition causing stroke and dementia , 1996, Nature.

[10]  T. Numakunai,et al.  Establishment of self-sterility of eggs in the ovary of the solitary ascidian, Halocynthia roretzi , 1996, Roux's archives of developmental biology.

[11]  N. Satoh,et al.  Expression of AMD 1, a gene for a MyoD 1-related factor in the ascidian Halocynthia roretzi , 1994, Roux's archives of developmental biology.

[12]  Tomoko Kameda,et al.  Self‐Nonself Recognition Activity Extracted from Self‐Sterile Eggs of the Ascidian, Ciona intestinalis , 1991, Development, growth & differentiation.

[13]  H. Fujita,et al.  Cytological Characterization of Self Incompatibility in Gametes of the Ascidian, Ciona intestinalis , 1987 .

[14]  M. Fuke Self and non-self recognition between gametes of the ascidian,Halocynthia roretzi , 1983, Wilhelm Roux's archives of developmental biology.

[15]  T. Numakunai,et al.  Evidence for participation of sperm proteinases in fertilization of the solitary ascidian, Halocynthia roretzi: effects of protease inhibitors. , 1981, Developmental biology.

[16]  T. Numakunai,et al.  Periodic spawning of three types of the ascidian, Halocynthia roretzi (Drasche), under continuous light conditions , 1980 .

[17]  F. Rosati,et al.  Role of the surface carbohydrates in sperm–egg interaction in Ciona intestinalis , 1980, Nature.

[18]  F. Rosati,et al.  Studies on fertilization in the Ascidans. I. Self-sterility and specific recognition between gametes of Ciona intestinalis. , 1978, Experimental cell research.

[19]  S. Tonegawa,et al.  Evidence for somatic rearrangement of immunoglobulin genes coding for variable and constant regions. , 1976, Proceedings of the National Academy of Sciences of the United States of America.

[20]  T. Morgan The genetic and the physiological problems of self-sterility in Ciona. V. The genetic problem , 1942 .

[21]  T. Morgan The genetic and the physiological problems of self-sterility in Ciona. I. Data on self- and cross-fertilization , 1938 .

[22]  T. Morgan Removal of the Block to Self-Fertilization in the Ascidian Ciona. , 1923, Proceedings of the National Academy of Sciences of the United States of America.

[23]  M. Matsumoto,et al.  Sperm-Egg Binding Mediated by Sperm α-l-Fucosidase in the Ascidian, Halocynthia roretzi , 2002 .

[24]  M. Kasahara Major histocompatibility complex : evolution, structure, and function , 2000 .

[25]  Kenji Matsuno,et al.  Notch signaling. , 1995, Science.

[26]  D. Labie,et al.  [The X chromosome, fetal hemoglobin and sickle cell anemia]. , 1991, Nouvelle revue francaise d'hematologie.

[27]  M. Hoshi Sperm glycosidase as a plausible mediator of sperm binding to the vitelline envelope in Ascidians. , 1986, Advances in experimental medicine and biology.

[28]  H. Yokosawa,et al.  Evidence for acrosin-like enzyme in sperm extract and its involvement in fertilization of the ascidian, Halocynthia roretzi , 1982 .