Roles of CD9 and CD9-containing exosomes in sperm-egg membrane fusion

Natsuko Kawano, Keiichi Yoshida, Yuichiroh Harada, Naoko Onami, Yuki Takezawa, Kenji Miyado

Research output: Contribution to journalArticlepeer-review


In fertilization, two types of gametes - sperm and egg-unite via a stepwise approach to create a fertilized cell, which is capable of naturally developing into a new individual. Notably, "membrane fusion" occurring intercellularly between a sperm and an egg is essential for fertilization. In mammals, sperm-egg fusion is, at least in part, mediated by two integral membrane proteins, sperm Izumo and egg CD9, and their roles are critical but unelucidated. A recent study showed that CD9-containing vesicles are released from wild-type eggs, and then exosome-like vesicles induce fusion between sperm and CD9-deficient eggs in vitro, even though CD9-deficient eggs are highly refractory to spermegg fusion. This result provides compelling evidence for the crucial involvement of CD9-containing, fusion-facilitating vesicles in sperm-egg fusion, and offers a new insight into gamete fusion and other membrane fusion events.

Original languageEnglish
Pages (from-to)191-197
Number of pages7
JournalJournal of Mammalian Ova Research
Issue number4
Publication statusPublished - 1 Oct 2010


  • CD9
  • Exosome
  • Fertilization
  • Membrone fusion


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