Insights into non-crossover recombination from long-read sperm sequencing

Area of Science:

• Genetics
• Molecular Biology
• Reproductive Biology

Background:

• Meiotic recombination generates genetic diversity through crossovers and gene conversions.
• Studying non-crossover gene conversion at the individual level is challenging.
• PRDM9 is a key regulator of meiotic recombination initiation.

Purpose of the Study:

• To develop a method for analyzing both crossover and non-crossover recombination events in human sperm.
• To investigate inter- and intra-individual variation in recombination rates.
• To explore the relationship between recombination types and PRDM9 binding sites.

Main Methods:

• Utilizing single high-fidelity long sequencing reads from human sperm.
• Analyzing fifteen sperm samples from thirteen donors.
• Characterizing crossover and non-crossover events, including gene conversion tract lengths.

Main Results:

• Demonstrated variation in recombination rates between and within donors.
• Observed non-crossover gene conversions upstream of PRDM9 binding sites, with crossovers showing a downstream bias.
• Identified two distinct non-crossover processes: a common short-tract type associated with PRDM9 and a rare long-tract type potentially independent of PRDM9.

Conclusions:

• Single sperm sequencing is a powerful tool for studying human recombination.
• Recombination patterns, including gene conversion, show donor-specific variation and are influenced by PRDM9.
• Two distinct non-crossover pathways exist, one standard and one potentially related to complex genomic rearrangements.