Our experiments have revealed the existence of a hitherto unknown, trans-acting, macromolecular regulatory system controlling the location and relative activity of mammalian recombination hotspots by activating, suppressing and modulating the activity of specific hotspots. Genetic variation of this regulatory system enabled its discovery and now provides a means of identifying its components and their interactions, an essential first step in understanding its relevance to issues of human genetics as well as questions of population biology and evolution. The locations of hotspots and their relative activity in humans and mice (our principal mammalian research model organism) determine patterns of linkage disequilibrium and the possibilities for closely linked genes to be coinherited, important issues in efforts to identify genes important in human health and disease. The first regulatory gene we identified, Prdm9, determines hotspot locations by activating recombination there;it has no quantitative modifiers, and its role is independent of gene dosage. Here we will investigate the complementary regulatory system controlling quantitative levels of hotspot activity, a matter of equal concern in elucidating the structure of this novel regulatory system and its ability to influence inheritance patterns. We will study the quantitative regulation of three hotspots whose activities are regulated by genes that differ between the mouse strains C57BL/6J and CAST/EiJ;two have their activity reduced by the presence of CAST alleles, and one has its activity enhanced. We will do so by applying a new, considerably improved, quantitative assay system for hotspot activities in sperm samples that relies on high throughput DNA sequencing;mapping and cloning the regulatory genes involved;testing their interactions with each other;determining whether they act in a dose dependent manner, indicating whether they act catalytically or stoichimetrically, and finally, testing whether they control the rate of initiation of recombination or the decision between the alternative recombination pathways leading to crossing over or the formation of non-crossover gene conversions. We expect to learn whether each hotspot has its own unique regulatory system or there are shared regulatory elements, whether up and down regulation are effected by the same genes, whether controls are exerted on the initiation of recombination or the choice between alternate pathways of recombination, and the manner in which any of these genes interact with each other. These data together with the molecular identity of these genes will likely provide important clues as to their mechanism of action. The answers to these questions will considerably enhance our understanding of one of the most basic biological processes, genetic recombination.
Genetic recombination is the biological process that enables us to screen human populations for genes determining human health and disease. The proposed experiments will enhance our ability to carry out such studies by increasing our understanding of how recombination is regulated. The findings are applicable to every human condition that is genetically influenced, including all of our major diseases.
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|Baker, Christopher L; Petkova, Pavlina; Walker, Michael et al. (2015) Multimer Formation Explains Allelic Suppression of PRDM9 Recombination Hotspots. PLoS Genet 11:e1005512|
|Baker, Christopher L; Kajita, Shimpei; Walker, Michael et al. (2015) PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination. PLoS Genet 11:e1004916|
|Walker, Michael; Billings, Timothy; Baker, Christopher L et al. (2015) Affinity-seq detects genome-wide PRDM9 binding sites and reveals the impact of prior chromatin modifications on mammalian recombination hotspot usage. Epigenetics Chromatin 8:31|
|Baker, Christopher L; Walker, Michael; Kajita, Shimpei et al. (2014) PRDM9 binding organizes hotspot nucleosomes and limits Holliday junction migration. Genome Res 24:724-32|
|Billings, Timothy; Parvanov, Emil D; Baker, Christopher L et al. (2013) DNA binding specificities of the long zinc-finger recombination protein PRDM9. Genome Biol 14:R35|
|Paigen, Kenneth; Petkov, Petko (2012) Meiotic DSBs and the control of mammalian recombination. Cell Res 22:1624-6|
|Paigen, Kenneth; Petkov, Petko (2010) Mammalian recombination hot spots: properties, control and evolution. Nat Rev Genet 11:221-33|
|Parvanov, Emil D; Petkov, Petko M; Paigen, Kenneth (2010) Prdm9 controls activation of mammalian recombination hotspots. Science 327:835|
|Ng, Siemon H; Madeira, Rose; Parvanov, Emil D et al. (2009) Parental origin of chromosomes influences crossover activity within the Kcnq1 transcriptionally imprinted domain of Mus musculus. BMC Mol Biol 10:43|
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