Fine-scale analysis of mechanisms and controlling factors in a meiotic recombination hotspot in dogs (canis familiaris)
Meiotic recombination re-shuffles genomes from one generation to the next. In humans and most other mammals, meiotic recombination events are clustered in 1-2 kb wide recombination hotspots, whose locations are determined in trans by the protein PR-domain containing 9 (PRDM9). Mice lacking PRDM9 direct recombination to promoters and functional elements, resulting in meiotic defects. Dogs (Canis familiaris) lack a functional copy of PRDM9, yet linkage data showed that historical recombination events cluster in functional elements, suggesting that there may be a mechanism enabling controlled recombination at these locations, and in the absence of PRDM9. However nothing is known about the de-novo activity of dog recombination hotspots and the patters of recombination resolution in this PRDM9 deficient species. I investigated a dog recombination hotspot for de-novo recombination events using pooled sperm typing, and uncovered high crossover frequencies affecting up to 1 % of sperm. Frequencies can differ by one order of magnitude between dogs. Fine-scale analysis of crossover-breakpoints revealed wide distributions of breaks across up to 10 kb within the hotspot region. I further detect asymmetric breakpoint distributions between crossover orientations and crossover-associated transmission distortion, suggesting biased recombination-initiation or -repair. This work is an elaborate fine-scale dissection of a mammalian PRDM9-independent active recombination hotspot.
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