期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：17
页码：9633-9636
DOI：10.1073/pnas.96.17.9633
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In the hermaphrodite ascidian Ciona intestinalis, the egg vitelline coat (VC) controls gamete self-nonself discrimination. Oocytes, after germinal vesicle breakdown, can be fertilized by both self and nonself sperm. However, a barrier to fertilization by self sperm progressively develops in the VC in the 3 hours after germinal vesicle breakdown. During this period, follicle cells attached to the outer surface of the VC release self-sterility factors that bind to the VC. Within the follicle cells, these factors (possibly peptides) are thought to be shuttled to the cell membrane by an hsp70 homolog (Cihsp70). In fact, antibodies to hsp70 block the development of self-sterility. Proteasomes are central to the production of antigen peptides. Specific inhibition of proteasome activity with clasto-lactacystin {beta}-lactone (CL{beta}L) prevented the onset of self-sterility, but had no effect once this process had started. CL{beta}L did not block fertilization by nonself sperm. The self-sterility factors were removed from mature oocytes by exposure to acidified media, and their biological activity was transferred to immature oocytes treated with CL{beta}L. The obvious high multiplicity of self-nonself recognition alleles involved in fertilization, and the involvement of an hsp70 and a proteasome in processing self-sterility factors, suggests that this system may be evolutionarily related to the vertebrate immune system.
