The control of stem cell proliferation is crucial during the whole life of an organism. In fact, stem cells are at the origin of every differentiated cell types populating tissues and organs, ensuring their proper development, function, and homeostasis. Defects in stem cell regulation can lead to developmental disorders and pathologies like cancer. Two factors are known to control germline stem cell (GSC) proliferation in C. elegans: nutrient uptake and the quantity of mature oocytes present in the proximal gonad. In the latter, oocyte accumulation promotes GSC quiescence, to prevent oocyte hyperaccumulation. Although we have identified DAF-18/PTEN, PAR-4/LKB-1 and AAK-1/AMPK as effectors of this negative feedback loop, other effectors are likely missing to join them together in a complete molecular cascade. That cascade somehow needs to sense oocyte abundancy and signal across several cells to modulate GSC proliferation. Here, we used an
oma-1;
oma-2 background to trigger oocyte accumulation and homeostatic inhibition of GSC proliferation. We then screened for mutants that caused oocyte hyperaccumulation, and thus phenocopied
aak-1;
oma-1;
oma-2 homeostatic-defective triple mutants. We screened approximately 8 000 haploid genomes over two separate screens, and isolated 17 candidates. Using whole-genome sequencing and bioinformatics tools, we identified a list of genes that had severe mutations in two or more of the isolated mutants. Among this list was
aak-1, which was severely disrupted in two of the candidates, demonstrating that the screening strategy was effective at isolating mutations that disrupt homeostatic signalling. We will next use RNAi to knockdown the remaining genes on our list and identify those that will cause a hyperaccumulation of oocytes upon RNAi inactivation. Positive clones will likely represent new genes involved in homeostatic regulation of GSC proliferation, and the corresponding genes will be further functionally investigated. Hence, our results will provide new insights into the mechanisms of homeostatic control of GSC proliferation.