Determining the roles of autophagy in gametogenesis in S. cerevisiae

PROJECT SUMMARY Gametogenesis, the intricate process of generating cells specialized in sexual reproduction through meiosis, necessitates a profound alteration in gene expression, organelle homeostasis, and programmed cell development and differentiation in the context of targeted proteolysis. Autophagy—a highly-conserved lysosomal degradation process—plays a crucial role in cell survival under diverse stress conditions and has emerged as a pivotal player in governing reproductive and developmental stages, including gametogenesis. In the yeast Saccharomyces cerevisiae, autophagy is active and essential at multiple stages including meiosis entry, DNA replication, meiosis exit and the subsequent daughter cell membrane biogenesis. Phenotypes associated with failed meiosis exit include aberrant spindle pole body (SPB, yeast centrosome) formation and chromosome segregation. To date, Cdc14, a conserved cell cycle phosphatase is the only meiosis-specific autophagy regulator identified. Cdc14 is involved in guiding autophagy at anaphase I to remove Rim4 selectively, a meiosis-specific RNA binding protein (RBP) that inhibits translation. This finding, from my laboratory, reveals a novel link between autophagy and temporal meiotic translation at a specific stage of meiosis, meiosis II, while critical autophagy functions and regulations at other stages of gametogenesis are yet to be revealed. On the other hand, yeast gametogenesis in nature is exposed to stresses, such as starvation, heat, and oxidation. I recently discovered meiosis-specific stress granules (SGs) triggered by stressors, including heat and oxidation. The SGs typically sequester mRNAs to inhibit translation until being disassembled during recovery, and autophagy degrades the persistent SGs. Intriguingly, meiotic SGs discovered in our study exhibit features including high heat sensitivity and autophagy resistance. Moreover, the capacity of meiotic SG formation correlates with the efficiency of meiotic DNA replication and gametogenesis. Nevertheless, the functions and regulation of meiotic SGs remain mysterious. Employing a multidisciplinary approach encompassing genetics, biochemistry, cellular imaging, proteomics, and computational methods, this proposal will investigate three overarching directions: D1) Determine how autophagy promotes gametogenesis; D2) Determine how gametogenesis regulates autophagy; and D3) Investigate how stresses affect autophagy and gametogenesis through stress granules (SGs). My investigation will primarily focus on the steps of meiosis but also cover pre-meiotic and post-meiotic stages of yeast gametogenesis. This research is poised to yield interdisciplinary conceptual breakthroughs in autophagy, gametogenesis, and stress responses. The revealed mechanisms, once confirmed in higher eukaryotes, including humans, will shed light on infertility, miscarriage, and specific human disorders like Turner syndrome (monosomy X, frequency: 1/2,500 newborn girls) and Down syndrome (trisomy 21, frequency: 1/800 newborns).