1. Research Background:

Female fertility strongly decreases with advancing maternal age, a phenomenon known as “reproductive aging”. As our society has been progressively delaying maternity since decades, the impact of reproductive aging is becoming increasingly relevant, with major social, economic, and demographic consequences. However, reproductive aging remains a poorly understood phenomenon for which there is currently no effective prevention or mitigation strategy.

Reproductive aging is largely driven by reduced oocyte quality with advanced maternal age. Oocytes, the female germ cells that develop into fertilizable eggs, are extremely long-lived cells that need to preserve their intracellular components to allow proper embryogenesis after fertilization. Protein homeostasis (proteostasis) is essential in all cell types to maintain intracellular integrity, and long-lived cells are particularly sensitive to its decay during aging. In the ProteOostasis lab, we are broadly interested in how proteostasis is regulated throughout the oocyte life, how it contributes to preserve oocyte quality, and whether its decline with age contributes to reproductive aging in mammals.

2. Research questions addressed by the group:

We have recently discovered (Zaffagnini et al., 2024) that mouse oocytes sequester and degrade aggregated proteins, a hallmark of impaired proteostasis, in novel “super-organelles” named ELVAs. ELVAs consist of clustered endosomes, lysosomes and autophagic vesicles (autophagosomes) embedded in a liquid-like condensate formed by RUFY1. Largely non-degradative in immature oocytes, ELVAs acquire degradative activity during the maturation of the oocyte into a fertilizable egg, thereby disposing of the sequestered aggregates and enabling proper embryogenesis. Our research currently focuses on understanding how ELVAs are assembled, how they sequester their cargos (aggregates), how they activate degradation, and how they are altered during reproductive aging. Our results will yield new mechanistic insight for the maintenance of proteostasis in long lived cells, and will shed new light on oocyte quality decline during female reproductive aging.

3. Possible projects:

1. In vitro and in vivo reconstitution of ELVAs. Vesicular trafficking to the lysosomes is tightly regulated during endocytosis and autophagy. In ELVAs, endosomes, autophagosomes and lysosomes are embedded in a liquid-like condensate, yet they are still capable of fusion to allow cargo degradation during oocyte maturation. How does vesicular trafficking occur inside a liquid-like matrix? How does RUFY1, the ELVA “glue” protein, assemble ELVAs and recruit vesicles? How is vesicular fusion specifically upregulated during oocyte maturation inside ELVAs? To answer these questions this project will aim to reconstitute ELVAs in vitro and in vivo, using recombinant proteins and purified components, followed by validations in cells and oocytes.

2. How ELVAs loss affects oocyte metabolism, ovarian dynamics, and reproductive aging. Our data indicate that loss of ELVAs results in altered lysosomal dynamics in the oocyte, which in turn affect female fertility and shorten the reproductive lifespan. How does lysosomal dynamics in the oocyte impact long-term fertility? To answer this question, this project will aim to characterize the molecular and functional consequences of ELVAs’ loss in oocytes, and to investigate how these alterations affect ovarian dynamics, fertility, and the female reproductive lifespan.

4. Applied Methods and model organisms:

We use a variety of methods and model systems, including in vitro reconstitutions, advanced fluorescence imaging, omics, microinjections, cultured cells, and primary mouse oocytes, providing a diverse, stimulating, and collaborative research environment.

5. Desirable skills and qualifications:

We are seeking for a highly motivated, proactive, and curiosity-driven candidate. Structured, creative thinking, rigorous experimentation and excellent teamwork skills are required, as well as basic experience in a molecular/cell biology lab (e.g., familiarity with routine lab techniques such as PCR, cell culture, etc.). Previous experience with oocytes, in vitro reconstitutions, and/or animal experimentation is nice to have, but not required. As projects may partially or entirely depend on the isolation of mouse oocytes and/or embryos, the candidate should not have a priori objections to work with experimental animals (mice).

6. References and key publications:

Zaffagnini G, et al. Mouse oocytes sequester aggregated proteins in degradative super-organelles. Cell. 2024. doi: 10.1016/j.cell.2024.01.031. PMID: 38382525.

Rosswag de Souza S, Böke E, Zaffagnini G. Proteostasis in cellular dormancy: lessons from yeast to oocytes. Trends Biochem Sci. 2025. doi: 10.1016/j.tibs.2025.05.004. PMID: 40506311.