Research Overview
The Villeneuve lab investigates the molecular and cellular events underlying the faithful inheritance of chromosomes during meiosis, the specialized cell division program by which diploid organisms generate haploid gametes. These events are crucial for reproduction, since failure to execute them correctly leads to aneuploidy, one of the leading causes of miscarriages and birth defects in humans. One major goal is to understand the mechanisms and regulation of genetic recombination, which is responsible both for reassortment of genetic traits and for promoting segregation of homologous chromosomes during meiosis. An inter-related goal is to understand how meiosis-specific chromosome organization is established, maintained, and remodeled to bring about successful genome inheritance. We approach these issues primarily using the nematode Caenorhabditis elegans, a simple organism that is especially amenable to combining sophisticated microscopic, genetic and genomic approaches in a single experimental system. Our research interrogates the process of meiosis at multiple different scales: 1) at the level of the DNA repair complexes that assemble at the sites of meiotic recombination; 2) at the level of the meiosis-specific chromosome structures that promote, regulate and respond to meiotic recombination events; 3) at the level of DNA organization at the whole-chromosome scale; and 4) at the level of cell biological mechanisms that promote developmental progression of meiosis and execute chromosome segregation.
Current Projects
Green Eggs & Him 2.0: An updated genetic screen to identify new meiotic genes
We have designed an updated version of our previous Green Eggs & Him (High Incidence of Males) screen (Kelly et al. 2000), which used a GFP-based reporter for detection of X chromosome missegregation/aneuploidy. Green Eggs & Him 2.0 incorporates: 1) new features to enable rapid screening and capture defects in multiple aspects of the meiotic program, and 2) an efficient and cost-effective pipeline, involving multiplexed whole genome sequencing (WGS) of un-backcrossed mutants to enable rapid identification of new meiotic genes. Chantal Akerib (Genetics Lead) and R. Yokoo (Sequencing Analysis Lead) have been integral to the success of this screen, and newly discovered genes are being investigated by many members of the V-lab!
Developing cytological methods for improved visualization of recombination site architecture and chromosome organization
Through a combination of super resolution imaging and our development of new cytological preparations of the C. elegans germline, we have revealed previously unrecognized structural features of meiosis that inform our thinking about meiotic processes. Specifically, we have visualized the architecture of crossover sites and the molecular stoichiometry of chromosome axes and developed image analysis approaches to facilitate the interpretation of complex data (Pattarbiraman et al 2017; Woglar and Villeneuve 2018; Woglar et al. 2020; Hinman et al 2021).
Caenorhabditis interspecies hybrid system for investigating meiotic mechanisms
We have validated a Caenorhabditis interspecies hybrid system as a new model for interrogating mechanisms of meiosis. Postdoc Charlotte Choi is using this system to test hypotheses regarding the mechanisms of homolog recognition and to investigate the modular organization of protein complexes underlying meiotic chromosome architecture in C. briggsae and C. nigoni sister species hybrids.
Mechanisms underlying robustness of crossover designation and maturation
We are exploring mechanisms that promote and ensure reliable crossover formation through investigating the designation, organization, and function of crossover-specific repair sites. Postdoc Celja Uebel is investigating COSA-2, a new factor required for meiotic crossover formation that was discovered in the Green Eggs and Him 2.0 genetic screen. She is exploring the potential for COSA-2, which is unstructured/intrinsically disordered, to promote accumulation and/or stabilization of pro-crossover factors at crossover-designated sites. This project seeks to illuminate mechanisms of disordered proteins in ensuring successful crossover formation.
Revealing hidden roles of RAD-54 family proteins in meiosis
In meiosis, efficient repair of programmed double-strand breaks (DSBs) is crucial for genome integrity and faithful chromosome segregation. Graduate student Kei Yamaya is investigating the in vivo functions of C. elegans RAD54 paralogs, RAD-54.L and RAD-54.B, during meiotic prophase. She has uncovered distinct contributions of these proteins to both the dynamics of RAD-51 association with DNA and the progression of meiotic DSB repair.
Weird Meiosis of Non-Model Nematode Species
We are examining the molecular and cellular bases of alterations in the meiotic program in a three-sexed nematode genus, Auanema, in which XX females, XX hermaphrodites and XO males co-exist in natural populations. Graduate student Liesl Strand is specifically investigating mechanisms driving sex- and gamete-specific modifications of the meiotic program that shape unusual patterns of sex chromosome inheritance in this genus. This project seeks to provide new insights into the unusual biology of these organisms and probe how fundamental features of the meiotic program can be modulated across evolutionary time.
Mechanisms of spindle assembly and chromosome segregation during oocyte meiosis
We are interested in understanding how microtubule-based mechanisms of chromosome segregation are modified during meiosis. Postdoc Emmanuel Nsamba is investigating how microtubule composition and proteins that interact with microtubules enable successful chromosome segregation during oocyte meiosis.
Coordinating the meiotic program through reversible protein modification
We are pursuing two different avenues investigating the roles and consequences of reversible protein modifications in meiosis:
1) Understanding how meiotic events are coordinated through counterbalancing activities of protein kinases and phosphatases (Roelens et al 2019), and 2) Investigating the roles of a newly-discovered putative deubiquitinating enzyme in assembly and maintenance of meiosis-specific structures, progression of DSB repair, and meiotic chromosome compaction.
