The histone-3-lysine-4-trimethyl(H3K4me3)transferase PRDM9 (PR domain containing 9) determines the sites of the double-stranded breaks (DSBs) initiating meiotic recombination in the mouse, human, and cattle by binding at specific DNA sequences known as hotspots. The rapid evolution of the DNA-binding domain of the PRDM9-encoding gene is a response to the consequences of the meiotic paradox (the most often used hotspots disappear most quickly from the population) that leads to new hotspots. Deletion of the Prdm9 gene from the laboratory mouse induces a shift of the DSBs to other H3K4me3 sites including promoters and a complete arrest of meiotic prophase I. Some organisms, such as dogs, birds, and baker´s yeast that lack PRDM9, have recombination hotspots that are conserved in closely related species and often located near promoters. We therefore investigated if PRDM9 is essential for meiosis in the wild mouse, using two types of Prdm9 mutations and two wild-derived mouse strains. We phenotyped these mice by indirect immunofluorescent labeling of spread nuclei to assess synapsis and DSB repair, finding that mutant phenotypes depend on genetic background. To reveal hotspot positions, the products of anti-H3K4m3 and anti-DMC1 (a DSB-repair protein) testicular chromatin immunoprecipitations were sequenced and analyzed. We will present the phenotyping results of these Prdm9-deficient mice including the epigenomic analyses.
This work was supported by the Czech Science Foundation (14-20728S), the Academy of Sciences of the Czech Republic (RVO 68378050), the project BIOCEV (CZ.1.05/1.1.00/02.0109), and the Czech MEYS (LM2011032, LQ1604). CLB, KP, and PMP were supported by NIH P01 grant GM099640 to KP and R01 grant GM078452 to PMP.