A role for synaptonemal complex in meiotic mismatch repair

Area of Science:

• Cell Biology
• Genetics
• Molecular Biology

Background:

• Meiotic recombination is crucial for genetic diversity.
• Synaptonemal complex (SC) formation is a hallmark of meiosis.
• The role of SC in homologous recombination and its associated repair pathways is not fully understood.

Purpose of the Study:

• To investigate the functional relationship between SC structure and homologous recombination, specifically mismatch repair.
• To determine if SC proteins influence the efficiency of mismatch repair during meiosis.
• To elucidate the molecular basis of postmeiotic segregation in SC-deficient mutants.

Main Methods:

• Analysis of Saccharomyces cerevisiae strains with mutations in SC central element proteins (Ecm11, Gmc2, Zip1).
• Assessment of postmeiotic segregation (PMS) events at the THR1 locus.
• High-throughput sequencing of meiotic products to analyze genome-wide recombination events and mismatch repair.
• Comparison of gene conversion tract lengths and per-nucleotide mismatch frequencies between wildtype and mutant strains.

Main Results:

• SC proteins are dispensable for recombination but essential for efficient mismatch repair at recombination sites.
• SC-deficient mutants (ecm11, gmc2, zip1[Δ21-163]) exhibit increased postmeiotic segregation.
• Genome-wide analysis reveals a higher frequency of recombination events with unrepaired mismatches in ecm11 mutants.
• While ecm11 mutants show longer gene conversion tracts, this alone doesn't explain the increased unrepaired mismatches; rather, a larger fraction of events are susceptible to inefficient repair.

Conclusions:

• SC structure plays a critical role in promoting the efficient mismatch repair of meiotic recombination intermediates.
• The absence of SC leads to elevated postmeiotic segregation, indicating a failure in mismatch repair.
• This finding applies to both MutSγ crossover-proficient and MutSγ crossover-deficient mutants, highlighting the broad importance of SC in ensuring meiotic fidelity.