Fig. 3. Aggregation kinetics of Q40-YFP in C. elegans muscle cells. (A) Fluorescence images of individual animals showing the increase in aggregates over different days of adulthood. Note that aggregation is only initiated once the animals are adults, in contrast to previous work using a strain with higher overexpression levels (Fig. 2). (B) Experimental data for four strains expressing the protein at different levels, fitted to a model based on independent nucleation events in individual cells. (C) The same dataset as in B, fitted to a model including cooperativity. In this model, which does not recapitulate the data well, the aggregation rate increases as a function of the aggregate mass already present, e.g. due to cell-to-cell spreading or a proteostasis decline. Based on ref. 49.