Homologous recombination during meiosis is essential for proper chromosome segregation and thus for formation of euploid gametes. Meiotic recombination is initiated by double-strand breaks (DSBs) made by the SPO11 protein. This proposal addresses molecular mechanisms underlying mammalian DSB formation and recombination, using mouse as a model system.
Aims are: 1. To define mechanisms that ensure X-Y recombination. Sex chromosomes pose significant challenges to male meiotic cells because the X and Y share only a small region of homology (the pseudoautosomal region, or PAR) within which DSB formation and recombination must occur in every meiosis. Studies supported by this grant uncovered unique structural properties and dynamic behaviors of the mouse PAR that appear critical for proper X-Y segregation. To define the molecular basis of these properties, the higher order structure of the PAR will be examined in female meiosis and in meiosis of males bearing a much longer PAR. These studies will determine what properties are intrinsic to the PAR. The genetic control of PAR recombination will also be examined, focusing on roles of SPO11 isoforms and the DNA damage response kinase ATM. 2. To elucidate mechanisms of meiotic recombination and the factors involved. Recombination leads to formation of both crossovers and noncrossovers;much is known about the pathways leading to these products in yeasts, but comparatively little is known about these mechanisms in mammals. These issues will be addressed using a novel assay that allows all chromatids involved in a single meiotic recombination event to be characterized. Using this mouse """"""""tetrad"""""""" assay, recombination patterns in wild-type spermatocytes will be delineated. Recombination in the absence of ATM function will also be examined. 3. To determine how ATM controls the number and distribution of DSBs. ATM homeostatically controls DSB numbers via a negative feedback loop, but the molecular basis of this regulation is unclear. To address this issue, the mechanism by which ATM is activated in response to SPO11- generated DSBs will be determined, focusing on the role of the MRE11-RAD51-NBS1 complex. In addition, a new method for genome-wide DSB mapping will be applied to Atm-/- spermatocytes to provide insight into the influence of ATM on the distribution of DSBs across the genome.

Public Health Relevance

Abnormal chromosome numbers in eggs or sperm cause developmental disabilities or miscarriage. These abnormalities often arise because of improper separation of chromosomes caused by defects in meiotic homologous recombination. This project will address fundamental questions about the mechanism and control of recombination.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-GGG-T (02))
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Janes, Daniel E
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Sloan-Kettering Institute for Cancer Research
New York
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Yamada, Shintaro; Kim, Seoyoung; Tischfield, Sam E et al. (2017) Genomic and chromatin features shaping meiotic double-strand break formation and repair in mice. Cell Cycle 16:1870-1884
Marcet-Ortega, Marina; Pacheco, Sarai; Martínez-Marchal, Ana et al. (2017) p53 and TAp63 participate in the recombination-dependent pachytene arrest in mouse spermatocytes. PLoS Genet 13:e1006845
Kim, Seoyoung; Peterson, Shaun E; Jasin, Maria et al. (2016) Mechanisms of germ line genome instability. Semin Cell Dev Biol 54:177-87
Lange, Julian; Yamada, Shintaro; Tischfield, Sam E et al. (2016) The Landscape of Mouse Meiotic Double-Strand Break Formation, Processing, and Repair. Cell 167:695-708.e16
Stanzione, Marcello; Baumann, Marek; Papanikos, Frantzeskos et al. (2016) Meiotic DNA break formation requires the unsynapsed chromosome axis-binding protein IHO1 (CCDC36) in mice. Nat Cell Biol 18:1208-1220
Luo, Mengcheng; Zhou, Jian; Leu, N Adrian et al. (2015) Polycomb protein SCML2 associates with USP7 and counteracts histone H2A ubiquitination in the XY chromatin during male meiosis. PLoS Genet 11:e1004954
Pacheco, Sarai; Marcet-Ortega, Marina; Lange, Julian et al. (2015) The ATM signaling cascade promotes recombination-dependent pachytene arrest in mouse spermatocytes. PLoS Genet 11:e1005017
Lam, Isabel; Keeney, Scott (2015) Mechanism and regulation of meiotic recombination initiation. Cold Spring Harb Perspect Biol 7:a016634
Ontoso, David; Kauppi, Liisa; Keeney, Scott et al. (2014) Dynamics of DOT1L localization and H3K79 methylation during meiotic prophase I in mouse spermatocytes. Chromosoma 123:147-64
Cole, Francesca; Baudat, Frédéric; Grey, Corinne et al. (2014) Mouse tetrad analysis provides insights into recombination mechanisms and hotspot evolutionary dynamics. Nat Genet 46:1072-80

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