The overall goal of this project is to determine how cells communicate chromosome break formation and repair across large chromosomal distances. DNA double-strand breaks (DSBs) are dangerous insults to genome integrity because of their potential to cause chromosome rearrangements and chromosome instability, both of which are strongly associated with cancer progression as well as birth defects. Remarkably, meiotic cells are able to efficiently orchestrate the formation and repair of hundreds of concurrent DSBs across their genome during meiotic recombination, a process that is essential for proper gamete formation and fertility. A key feature of meiotic DSB formation and repair is its coordination at the chromosomal level. In the previous funding period we provided evidence that the synaptonemal complex, a conserved protein lattice that forms between aligned homologous chromosomes in late meiotic prophase, communicates repair decisions along meiotic chromosomes in S. cerevisiae. We showed that this communication resulted in reduced DSB formation as well as simplified repair, and we identified several factors involved in this process. We now discovered the existence of privileged genomic regions near the ends of all chromosomes that appear resistant to regulation by the synaptonemal complex. These end-adjacent regions (EARs) cover large genomic distances (~100kb, which is nearly half the length of the shortest chromosome) and continue to form and repair DSBs well after DSB formation has stopped in the rest of the genome. Similar regions of elevated meiotic recombination are also observed in birds, chimps, and humans. The goal of this project is to define the chromosomal signal that generates these regions and to test if EARs help inheritance of short chromosomes. Our preliminary analyses suggest several roles of the nuclear envelope, both in the establishment of the EARs and in the suppression of DSBs in the rest of the genome. The dynamics of chromosomal signaling and its interaction with the nuclear envelope will be analyzed by genome-wide binding studies and super-resolution microscopy, taking advantage of a conditional nuclear depletion approach that we recently introduced into meiotic cells that allows stage-specific knock-downs of pleiotropic nuclear factors. In addition, signal integration will be analyzed using genetic epistasis analyses, cytology, and physical analysis of DSB formation. As EARs cover a proportionally much larger fraction of short chromosomes, the proposal will also use tetrad sequencing to test if these regions drive the widely observed increase in recombination rates on short chromosomes. Fluorescent marker segregation will be used to determine if EARs differentially improve the meiotic segregation fidelity of short chromosomes. Together, these analyses will provide key insights into the mechanisms of chromosomal signal propagation, and open new avenues for understanding the origins of birth defects such as Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18), which are caused by meiotic missegregation of short chromosomes.

Public Health Relevance

Errors in packaging short chromosomes into sperm or egg cells are principally responsible for the high incidence of chromosomal birth defects such as Down syndrome (trisomy 21) and Edwards syndrome (trisomy 18). This project aims to determine the molecular mechanisms that specifically support the inheritance of short chromosomes in the model organism Saccharomyces cerevisiae, which, like humans, has a wide range of chromosome sizes. The results from this work will provide a general framework for the study of chromosomal birth defects in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM111715-06S1
Application #
10217794
Study Section
Program Officer
Keane-Myers, Andrea
Project Start
2015-03-01
Project End
2023-05-31
Budget Start
2020-06-01
Budget End
2021-05-31
Support Year
6
Fiscal Year
2021
Total Cost
Indirect Cost
Name
New York University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
041968306
City
New York
State
NY
Country
United States
Zip Code
10012
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Paul, Matthew Robert; Hochwagen, Andreas; Ercan, Sevinç (2018) Condensin action and compaction. Curr Genet :
Mansisidor, Andrés; Molinar Jr, Temistocles; Srivastava, Priyanka et al. (2018) Genomic Copy-Number Loss Is Rescued by Self-Limiting Production of DNA Circles. Mol Cell 72:583-593.e4
Markowitz, Tovah E; Suarez, Daniel; Blitzblau, Hannah G et al. (2017) Reduced dosage of the chromosome axis factor Red1 selectively disrupts the meiotic recombination checkpoint in Saccharomyces cerevisiae. PLoS Genet 13:e1006928
Argunhan, Bilge; Leung, Wing-Kit; Afshar, Negar et al. (2017) Fundamental cell cycle kinases collaborate to ensure timely destruction of the synaptonemal complex during meiosis. EMBO J 36:2488-2509
Subramanian, Vijayalakshmi V; MacQueen, Amy J; Vader, Gerben et al. (2016) Chromosome Synapsis Alleviates Mek1-Dependent Suppression of Meiotic DNA Repair. PLoS Biol 14:e1002369