Interplay between structure-specific endonucleases for crossover control during Caenorhabditis elegans meiosis

Area of Science:

• Genetics
• Molecular Biology
• Cell Biology

Background:

• Crossover (CO) formation in meiosis I is essential for accurate chromosome segregation.
• Structure-specific endonucleases like MUS-81, SLX-1, XPF-1, and GEN-1 are implicated in resolving Holliday junctions for COs.
• The precise coordination and distinct roles of these nucleases in CO control remain incompletely understood.

Purpose of the Study:

• To elucidate the functional overlap and differences among MUS-81, SLX-1, XPF-1, and GEN-1 in CO formation and regulation.
• To investigate the roles of these nucleases in meiotic recombination and chromosomal stability in Caenorhabditis elegans.
• To propose a model for the coordinate action of nucleases in meiotic crossover control.

Main Methods:

• Genetic analysis of single, double, triple, and quadruple mutants of structure-specific endonucleases in C. elegans.
• Biochemical assays to assess nuclease binding to the HIM-18/SLX4 scaffold.
• High-resolution imaging to examine crossover designation, frequency, distribution, and chromosomal morphology.

Main Results:

• MUS-81, XPF-1, and SLX-1 bind to the HIM-18/SLX4 scaffold; GEN-1 does not.
• MUS-81 and SLX-1, but not XPF-1 or GEN-1, show overlapping roles with HIM-6 in processing recombination intermediates.
• XPF-1 acts redundantly with MUS-81 and SLX-1 for CO formation during double-strand break repair.
• SLX-1 is essential for suppressing crossovers in the central autosomal regions.
• SLX-1 and XPF-1 are critical for maintaining meiotic chromosomal stability.

Conclusions:

• XPF-1, MUS-81, and SLX-1 function collaboratively in meiotic crossover formation.
• SLX-1 plays a dual role in promoting crossovers at chromosome arms and suppressing them centrally.
• SLX-1 and XPF-1 contribute to meiotic chromosomal stability by preventing abnormalities.
• A model of coordinate nuclease action is proposed for precise crossover control across different chromosomal domains.