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The putative chaperone calmegin is required for sperm fertility
1Research Institute for Microbial Diseases, Osaka University, Suita, Japan.
Nature
|June 5, 1997
Summary
Calmegin, an endoplasmic reticulum chaperone, is crucial for male fertility. Its absence causes sperm to fail binding to eggs, leading to infertility, similar to some human cases.
Area of Science:
- Molecular Biology
- Reproductive Biology
- Cell Biology
Background:
- Proper folding of membrane proteins in the endoplasmic reticulum (ER) is essential for protein function.
- Calnexin is a key ER chaperone involved in protein quality control.
- Calmegin is a testis-specific protein homologous to calnexin.
Purpose of the Study:
- To investigate the physiological function of calmegin in spermatogenesis and male fertility.
- To analyze the effects of calmegin deficiency on sperm-egg interactions.
Main Methods:
- Targeted gene disruption to create calmegin-null mice.
- Analysis of spermatogenesis and sperm morphology in null mice.
- In vitro assessment of sperm adhesion to the zona pellucida.
Main Results:
- Homozygous-null male mice exhibited near sterility despite normal spermatogenesis and mating behavior.
- Sperm from calmegin-null males showed defective adhesion to the egg's zona pellucida in vitro.
- This adhesion defect is proposed to be the cause of infertility.
Conclusions:
- Calmegin acts as a chaperone for sperm surface proteins involved in egg interaction.
- Calmegin deficiency leads to a specific sperm-egg binding defect, causing male infertility.
- The calmegin-deficient phenotype may offer insights into unexplained human male infertility.