Spermatozoa lacking Fertilization Influencing Membrane Protein (FIMP) fail to fuse with oocytes in mice
Open Access
- 15 April 2020
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 117 (17), 9393-9400
- https://doi.org/10.1073/pnas.1917060117
Abstract
Sperm–oocyte fusion is a critical event in mammalian fertilization, categorized by three indispensable proteins. Sperm membrane protein IZUMO1 and its counterpart oocyte membrane protein JUNO make a protein complex allowing sperm to interact with the oocyte, and subsequent sperm–oocyte fusion. Oocyte tetraspanin protein CD9 also contributes to sperm–oocyte fusion. However, the fusion process cannot be explained solely by these three essential factors. In this study, we focused on analyzing a testis-specific gene 4930451I11Rik and generated mutant mice using the CRISPR/Cas9 system. Although IZUMO1 remained in 4930451I11Rik knockout (KO) spermatozoa, the KO spermatozoa were unable to fuse with oocytes and the KO males were severely subfertile. 4930451I11Rik encodes two isoforms: a transmembrane (TM) form and a secreted form. Both CRISPR/Cas9-mediated TM deletion and transgenic (Tg) rescue with the TM form revealed that only the TM form plays a critical role in sperm–oocyte fusion. Thus, we renamed this TM form Fertilization Influencing Membrane Protein (FIMP). The mCherry-tagged FIMP TM form was localized to the sperm equatorial segment where the sperm–oocyte fusion event occurs. Thus, FIMP is a sperm-specific transmembrane protein that is necessary for the sperm–oocyte fusion process.Keywords
Funding Information
- MEXT | Japan Society for the Promotion of Science (JP15H05573)
- MEXT | Japan Society for the Promotion of Science (JP16KK0180)
- MEXT | Japan Society for the Promotion of Science (JP18K16735)
- MEXT | Japan Society for the Promotion of Science (JP18K14612)
- MEXT | Japan Society for the Promotion of Science (JP25112007)
- MEXT | Japan Society for the Promotion of Science (JP17H01394)
- MEXT | Japan Society for the Promotion of Science (JP19H05750)
- Japan Agency for Medical Research and Development (JP18gm5010001)
- National Cerebral and Cardiovascular Center (30-2-5)
- National Cerebral and Cardiovascular Center (31-6-3)
- HHS | NIH | Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD088412)
- HHS | NIH | Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD088412)
- HHS | NIH | Eunice Kennedy Shriver National Institute of Child Health and Human Development (P01HD087157)
- HHS | NIH | Eunice Kennedy Shriver National Institute of Child Health and Human Development (P01HD087157)
- Bill and Melinda Gates Foundation (INV-001902)
- Bill and Melinda Gates Foundation (INV-001902)
- P30 Cancer Center Support (NCI CA125123)
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