Novel PLCZ1 mutation caused polyspermy during in vitro fertilization

Area of Science:

• Reproductive Biology
• Human Genetics
• Developmental Biology

Background:

• Oocyte activation failure, including polyspermy and abnormal pronuclear (PN) formation, leads to early embryonic arrest.
• While phospholipase C zeta 1 (PLCZ1) mutations are known to cause PN formation failure after intracytoplasmic sperm injection (ICSI), their role in polyspermy during in vitro fertilization (IVF) is unclear.

Purpose of the Study:

• To investigate the association between PLCZ1 mutations and polyspermy in patients undergoing IVF.
• To explore the functional impact of PLCZ1 mutations on oocyte activation and pronuclear formation.
• To assess the efficacy of assisted oocyte activation (AOA) in overcoming fertilization defects caused by PLCZ1 mutations.

Main Methods:

• Whole-exome sequencing (WES) was employed to identify candidate PLCZ1 mutations in infertile couples.
• Sanger sequencing was utilized for mutation validation.
• Experiments involving the injection of PLCZ1-mutated sperm into human and mouse oocytes were conducted to assess PN formation.
• Assisted oocyte activation (AOA) was performed post-ICSI to manage fertilization failures.

Main Results:

• Three PLCZ1 mutations, including a novel missense mutation (c.1154C>T, p.R385Q), were identified in patients experiencing polyspermy during IVF.
• PN formation failure was observed during ICSI cycles with these mutations.
• Injection of multiple PLCZ1-mutated sperm successfully induced PN formation, indicating sperm-derived calcium oscillations exceeded the threshold for PN formation.
• AOA post-ICSI resulted in normal fertilization and successful pregnancies for all affected patients.

Conclusions:

• The findings expand the known spectrum of PLCZ1 mutations and highlight its role in preventing polyspermy.
• PLCZ1 mutations are associated with sperm-derived polyspermy and subsequent fertilization failure.
• This research offers valuable insights for genetic diagnoses of abnormal fertilization and suggests AOA as a potential therapeutic strategy for patients with PLCZ1-related polyspermy.