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Updated: Mar 1, 2026
09:24
Preparation of Meiotic Chromosome Spreads from Mouse Oocytes for Assessment of Synapsis and Recombination
Published on: July 18, 2025
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Replication-dependent early meiotic requirement for Spo11 and Rad50
S T Merino1, W J Cummings, S N Acharya
1Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Summary
Spo11 and Rad50 proteins are crucial for meiotic chromosome synapsis, but their role in forming the synaptonemal complex (SC) partially depends on premeiotic DNA replication in Coprinus cinereus.
Area of Science:
- Molecular and Cellular Biology
- Genetics and Genomics
- Meiosis and Recombination
Background:
- Spo11 and the Rad50-Mre11 complex are implicated in DNA replication and essential for programmed DNA double-strand breaks initiating meiotic recombination.
- Mutants lacking Spo11 or Rad50 exhibit defects in chromosome synapsis during meiosis in both Saccharomyces cerevisiae and Coprinus cinereus.
- The synaptonemal complex (SC) is a protein structure that mediates homologous chromosome pairing and recombination during meiosis.
Purpose of the Study:
- To investigate the role of Spo11 and Rad50 in meiotic chromosome synapsis in Coprinus cinereus.
- To determine if premeiotic DNA replication is required for the function of Spo11 and Rad50 in synaptonemal complex (SC) formation.
- To elucidate the dependency of SC formation on Spo11 and Rad50 in relation to premeiotic S phase.
Main Methods:
- Construction of double mutants combining spo11-1 or rad50-4 with spo22-1, a mutant that prevents premeiotic DNA replication.
- Microscopic analysis of nuclear structures, including axial elements (AE) and synaptonemal complex (SC), in wild-type and mutant strains.
- Quantification of nuclei containing AE and SC structures and measurement of AE and SC numbers in different mutant backgrounds.
Main Results:
- Partial restoration of synapsis was observed in C. cinereus spo11 and rad50 mutants when premeiotic DNA replication was prevented.
- Double mutants (spo11-1/spo22-1 and rad50-4/spo22-1) showed increased percentages of nuclei with SC structures and decreased percentages with AE only or no structures.
- Significant increases in the average numbers of AE and SC were noted in the double mutants, indicating a partial rescue of synapsis.
Conclusions:
- Spo11-induced recombination is not absolutely required for synapsis in Coprinus cinereus.
- The early meiotic role of Spo11 and Rad50 in SC formation is partially dependent on premeiotic S phase.
- This dependency may reflect requirements imposed by the replication process itself or the presence of sister chromatids during synapsis.
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