Evidence of a recombination rate valley in human regulatory domains

Human recombination rate varies greatly, but the forces shaping it remain incompletely understood. Here, we study the relationship between recombination rate and gene-regulatory domains defined by a gene and its linked control elements. We define these links using methylation quantitative trait loci (meQTLs), expression quantitative trait loci (eQTLs), chromatin conformation, and correlated activity across cell types. Each link type shows a “recombination valley” of significantly-reduced recombination rate compared to control regions, indicating preferential co-inheritance of genes and linked regulatory elements as a single unit. This recombination valley is most pronounced for gene-regulatory domains of early embryonic developmental genes, housekeeping genes, and constitutive regulatory elements, which are known to show increased evolutionary constraint across species. Recombination valleys show increased DNA methylation, reduced double-stranded break initiation, and increased repair efficiency, specifically in the lineage leading to the germ line, providing a potential molecular mechanism facilitating their maintenance by exclusion of recombination events.