Sex differences in PRDM9-independent fine-scale recombination patterns

Abstract

Meiotic recombination rates exhibit strong, fine-scale variation along the genome of many eukaryotes. In some animals, including humans, the protein PRDM9 directs recombination toward so-called recombination hotspots. However, in birds and dogs, which have lost PRDM9, hotspots generally occur in promoter sequences called CpG islands. Furthermore, in many species, recombination rates and patterns differ between the sexes, a phenomenon known as heterochiasmy. While sex differences in recombination rates and broad-scale genomic variation are rather well documented, far less is known about differences in fine-scale variation, with no insight from PRDM9-lacking animals. In this study, using thousands of high-resolution crossovers, I demonstrate that fine-scale recombination patterns are globally similar between the sexes in both dogs and barn owls. However, I show that recombination in protein-coding gene promoters is heavily male-biased in both species. Overall, the shared patterns of fine-scale heterochiasmy between these two amniotes shed light on both the sex-specific regulation of recombination and the evolutionary forces that shape it.