Deficiency in fertilization by morphologically abnormal sperm produced by azh mutant mice

Area of Science:

• Reproductive Biology
• Genetics
• Mammalian Reproduction

Background:

• The azh mutation in male mice causes infertility.
• Homozygous azh/azh males show drastically reduced fecundity (5-10% of wild-type).
• Understanding the cause of this infertility is crucial for reproductive research.

Purpose of the Study:

• To investigate the underlying causes of infertility in male mice homozygous for the azh mutation.
• To determine the specific stage of reproduction affected by the azh mutation.

Main Methods:

• Evaluated endocrine function and mating behavior in azh/azh male mice.
• Assessed sperm motility parameters, including hyperactivation and acrosome reactions.
• Conducted in vitro fertilization assays using various oocyte preparations (cumulus-intact/zona-intact, cumulus-free/zona-intact, zona-free).

Main Results:

• No gross endocrine disorders or mating behavior deficits were observed in azh/azh males.
• Sperm showed normal motility and acrosome reaction but slight reductions in some motility parameters.
• In vitro fertilization revealed failure to penetrate zona-intact oocytes but success with zona-free oocytes.

Conclusions:

• The primary defect in azh/azh male infertility is related to sperm quality, likely abnormal sperm morphology.
• The infertility manifests at the level of sperm interaction with the zona pellucida.
• The azh mutation significantly impacts the male gamete's ability to fertilize oocytes.