Guylain Boissonneault, Ph. D.
Genetic Instability of the Haploid Male Germ Cell
Stability of genetic information is of crucial importance for the normal function and reproduction of all living organisms. In heterogametic species, this stability must be maintained in somatic cells but also and most importantly in germline cells. Male and female gametes form the basis of every new individual, and their genomes’ integrity ensures faithful transmission of genetic information to the next generation.
Recent data from the literature suggest that transmission of point mutations and chromosomal rearrangements are primarily from paternal origin. Although meiosis is a well-known source of genetic instability, Doctor Boissonneault's research activities over the past seven years have focused on the haploid spermatids. Spermatids undergo a striking change in chromatin structure.
His working hypothesis is that this important transition represents a major source of genetic instability that has probably been overlooked by reproductive biologists. His team first established that elongating spermatids display DNA strand breaks that are part of the developmental program of these cells and may be required to support the change in DNA topology. Double-stranded breaks are being generated, and, given the haploid character of spermatids, these endogenous breaks cannot be repaired by homologous recombination but by an error-prone process related to the Non-Homologous End Joining (NHEJ). Hence, chromatin-remodeling steps in spermatids may be intrinsically mutagenic creating a slight genetic drift from one generation to the next without the need for exogenous genotoxic factors. Doctor Boissonneault's goal is to determine the origin of the transient DNA strand breaks, their genome-wide distribution, their mutagenic potential, the DNA repair mechanism involved and the sensitivity of this transition to genotoxic agents such as those used for chemotherapy. Histone hyperacetylation is apparently necessary for the formation of DNA strand breaks and the team is investigating the role of non-enzymatic histone acetylation in this process.
They have set up a new technique for the genome-wide mapping of DNA strand breaks and are currently developing a strategy to determine the potential genetic polymorphism induced by the transition process. Their recent immunofluorescence studies confirm that a DNA repair system compatible with NHEJ is present so that errors may clearly be generated.
This research program should confirm that this sensitive transition adds up to meiosis as a crucial determinant of genetic diversity with important consequences for evolution.
- First team to demonstrate that transient DNA strand breaks are part of the developmental program of spermatids. This may represent a new source of instability leading to genetic polymorphism transmittable to the next generation as well as new component of evolution
- Development of new cellular and molecular biology tools including the genome-wide mapping of DNA strand breaks wit broad applications for the study of DNA damage on a global scale (This has generated many local and international collaborations)
- Funding from major funding agencies including the CIHR and NSERC
- Active member of the Québec’s Network in Reproductive Biology (RQR)
Know-How & Opportunities for Collaboration
- Reproduction, spermatogenesis, DNA repair, chromatin
- Specific technical expertise
- Genome-wide mapping of DNA damage
- Germ cells separation by flow cytometry
- Assessment of DNA fragmentation (comet, PFGE, TUNEL assays)
- Capture techniques for high throughput sequencing (ChIP, RNA seq)
- Basic proteomics
- Cell culture and gene transfer