Germ Granule Remodeling Reveals Germline Age in Caenorhabditis elegans

Germline aging limits reproductive lifespan, yet quantitative measures of germline age at cellular resolution within intact tissue remain limited. Here, we show that two germline condensates, P granules and Mutator foci, undergo systematic age-associated remodeling in Caenorhabditis elegans, changing in morphology, spatial organization, and mutual associations. From these single-nucleus features, we develop Germ Granule Clock (GG-Clock), an image-based aging clock that accurately predicts chronological age. Intermittent fasting, a pro-longevity intervention, shifts GG-Clock predictions toward a younger germline state, demonstrating the clock's responsiveness to anti-aging interventions. To make the approach broadly usable, we introduce GGProfiler, an open-source tool that automates granule segmentation and feature extraction. Together, our findings establish germ granule architecture as an interpretable, image-based readout of germline aging and provide a platform for quantifying condensate remodeling across genetic and environmental interventions, with potential translation to other systems.