A Mutation in Mtap2 Is Associated with Arrest of Mammalian Spermatocytes before the First Meiotic Division

Area of Science:

• Reproductive Biology
• Genetics
• Cell Biology

Background:

• Meiosis is a fundamental process for sexual reproduction, conserved across species.
• Despite its importance, many genes regulating mammalian meiosis remain unidentified.

Purpose of the Study:

• To identify novel genes controlling mammalian meiosis using a forward genetic screen.
• To investigate the function of identified genes in spermatogenesis.

Main Methods:

• Utilized N-ethyl-N-nitrosourea (ENU) mutagenesis in mice to generate mutations.
• Conducted a screen to identify mutations affecting male meiosis.
• Performed deep sequencing to identify the causative mutation in the repro4 mutant.
• Analyzed MTAP2 transcript levels in mutant testes.

Main Results:

• The repro4 mutation causes spermatocytes to arrest at the G2/MI transition, failing to exit meiotic prophase I.
• Key meiotic prophase I events and known regulators of the G2/MI transition were unaffected in mutant cells.
• A mutation was identified in an intron of the Mtap2 gene, leading to reduced Mtap2 transcript levels.
• Microtubule-associated protein 2 (MTAP2) is implicated in male meiosis.

Conclusions:

• MTAP2 is essential for the completion of meiosis and normal spermatogenesis in mammals.
• The repro4 mutation highlights a novel role for MTAP2 in regulating the G2/MI transition during meiosis.