Mapping of meiotic recombination in human preimplantation blastocysts.

Recombination is essential for physical attachments and genetic diversity. The Han Chinese population is the largest ethnic group worldwide, therefore, construction of a genetic map regarding recombination for the population is essential. In this study, 164 and 240 couples who underwent preimplantation genetic testing for monogenic diseases (PGT-M) or segmental rearrangement (PGT-SR) were included in analysis. Blastocysts and probands from couples who underwent PGT-M by single nucleotide polymorphism (SNP) array were included for recombination analysis. Location of recombination was determined from haplotype phase transitions in parent-offspring pairs at loci where the parents were heterozygous. The genetic map for Chinese in vitro fertilization embryos was constructed by the expectation-maximization algorithm with chip-level data. Our results confirmed that homologous recombination (HR) occurred more often in maternal chromosomes, and the age effect was more significant in maternal HR. A total of 6,494 HR hotspots (32.3%) were identified in genes of Online Mendelian Inheritance in Man (OMIM). A uniform association between HR and aneuploidy was not established. In addition, carriers with identified breakpoints of reciprocal translocations were analyzed, and locations of breakpoints were found partly overlapped with HR hotspots, implying a possible similar mechanism behind both events. This study highlights the significance of constructing a recombination map, which may improve the accuracy of haplotype analysis for PGT-M. Overlapping locations of translocation and recombination are worthy of further investigation.