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Updated: May 28, 2026
Medium-throughput Screening Assays for Assessment of Effects on Ca2+-Signaling and Acrosome Reaction in Human Sperm
Published on: March 1, 2019
Function of the acrosomal matrix: zona pellucida 3 receptor (ZP3R/sp56) is not essential for mouse fertilization
Yuko Muro1, Mariano G Buffone, Masaru Okabe
1Research Institute for Microbial Diseases, Osaka University, Suita, Japan.
Abstract:
In mammalian fertilization, sperm-zona pellucida binding is considered to be a critical aspect of gamete interaction. In this study, we examine the mouse sperm acrosomal matrix protein zona pellucida 3 receptor (ZP3R; formerly called sp56) because of our interest in defining the function of the acrosomal matrix, the particulate compartment within the sperm secretory acrosome. Using targeted deletion of the Zp3r gene by homologous recombination, we examined the fertility of nullizygous animals. Our experiments showed that males and females homozygous for the affected gene exhibited no differences in litter sizes compared to wild-type and heterozygous animals. Testis weights of nullizygous males were equivalent to those of wild-type and heterozygous males, and no differences in the number of sperm produced by mice of three genotypes were found. In vitro fertilization rates using cumulus-intact and cumulus-free oocytes were also equivalent. Examination of sperm-binding zonae of unfertilized eggs and the ability of the sperm to undergo acrosomal exocytosis in response to calcium ionophore A23187 displayed no differences between wild-type, heterozygous, and nullizygous mouse sperm. These results provide further evidence that either ZP3R is not involved in sperm-zona pellucida binding or this process might be functionally redundant, involving multiple proteins for gamete interactions.
Insights
The zona pellucida 3 receptor (ZP3R) is not essential for mouse fertility or sperm-zona pellucida binding. This study suggests ZP3R may not play a critical role in fertilization, or other proteins compensate for its function.
Area of Science:
- Reproductive Biology
- Molecular Genetics
- Cell Biology
Background:
- Sperm-zona pellucida binding is crucial for mammalian fertilization.
- The acrosomal matrix contains proteins like zona pellucida 3 receptor (ZP3R), formerly sp56.
- The precise function of ZP3R in gamete interaction remains unclear.
Purpose of the Study:
- To investigate the role of zona pellucida 3 receptor (ZP3R) in mammalian fertilization.
- To determine the necessity of ZP3R for sperm-zona pellucida binding and overall fertility.
Main Methods:
- Targeted deletion of the Zp3r gene in mice using homologous recombination.
- Assessment of fertility, litter size, testis weight, and sperm count in nullizygous, heterozygous, and wild-type mice.
- In vitro fertilization assays and examination of sperm-zona binding and acrosomal exocytosis.
Main Results:
- Nullizygous mice (lacking ZP3R) showed no significant differences in fertility or litter size compared to controls.
- Sperm production, testis weight, and in vitro fertilization rates were equivalent across all genotypes.
- No differences were observed in sperm-zona binding or acrosomal exocytosis between ZP3R-deficient and wild-type sperm.
Conclusions:
- ZP3R is not essential for successful sperm-zona pellucida binding or fertilization in mice.
- Fertilization may involve functional redundancy, with multiple proteins contributing to gamete interaction.
- The specific role of ZP3R in the acrosomal matrix requires further investigation.
